JPH11200931A - Solenoid valve driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep an ON state of a solenoid valve at least for a required shortest period even when abnormality occurs at a constant-current circuit. SOLUTION: A solenoid valve driving circuit 5 adapted to a high pressure fuel control device of a vehicular engine supplies voltage to be required for driving a fuel injection valve 3 upon receiving a solenoid valve driving signal, and opens a solenoid valve 17 of the fuel injection valve 3. The solenoid valve driving circuit 5 has a constant-current circuit which generates specified constant current, and a plurality of charging means (capacitors) which sotores voltage higher than the power source voltage. High voltage of the charging means is discharged at once at the starting time of driving the solenoid valve 17. The ON state of the solenoid valve 1.7 is kept by the constant current of the constant-current circuit. A microcomputer 4 executes pilot injection and main injection with respect to the cylinder of the engine. The microcomputer 4 judges presence/absence of abnormality of the constant-current circuit. When abnormality presence is determined, discharging is continuously performed by the plural charging means, and thereby one fuel injection is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solenoid valve driving device, and more particularly to a solenoid valve driving device for driving a solenoid valve of a fuel injection valve so as to be applied to a fuel injection control device of a diesel engine and to perform a main injection and a pilot injection preceding the main injection. The present invention relates to a solenoid valve driving device for performing the operation.

[0002]

2. Description of the Related Art As a method of driving a solenoid valve at high speed, a voltage higher than a battery voltage (power supply voltage) is previously stored in a capacitor, and a high voltage is discharged from a capacitor to a driving solenoid at a stretch (peak current is supplied). In some cases, a constant current (hold current) generated from a battery voltage flows. According to such a method, the magnetic flux in the solenoid for driving the solenoid valve is sharply raised, so that a high-speed ON operation can be realized, and the ON state thereafter can be maintained for a desired period. Also, in a fuel injection control device for performing two fuel injections of a pilot injection and a main injection to one cylinder during one cycle of the engine, a charging circuit for charging two capacitors for the pilot injection and the main injection is provided. ,
2. Description of the Related Art A technique for forming an electromagnetic valve driving device by using one constant current circuit has been disclosed (for example, Japanese Patent Application Laid-Open No. 9-89).
147 publication).

[0003]

However, when an abnormality occurs due to an open failure of the constant current circuit, the constant current after the peak current stops flowing. Therefore, after the solenoid valve is driven by the peak current, the on-state (drive state) of the solenoid valve cannot be maintained, and the original on-time of the solenoid valve cannot be secured. When applied to the fuel injection control device as described above, a sufficient fuel injection amount cannot be obtained, and there is a problem that the engine falls into an extremely low speed operation or the engine stalls at worst. In other words, when the constant current circuit is abnormal, the driving energy of the solenoid valve is only the electric charge stored in the two capacitors for pilot injection and main injection. The fuel injection amount cannot be secured.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problem, and has as its object to maintain the ON state of the solenoid valve at least for a minimum necessary time even when an abnormality occurs in the constant current circuit. It is an object of the present invention to provide an electromagnetic valve driving device capable of performing the above-mentioned operations.

[0005]

The solenoid valve driving device according to the present invention is based on the premise that a constant current circuit for generating a predetermined constant current from a power supply voltage and a plurality of charging means for storing a voltage higher than the power supply voltage. The high voltage of the charging means is discharged at a burst at the beginning of driving of the solenoid valve, and the solenoid valve is kept on by the constant current of the constant current circuit.

According to the first aspect of the present invention, the first driving means discharges a high voltage by the plurality of charging means to drive the solenoid valve at predetermined intervals. In addition, when the second driving unit determines that the constant current circuit is abnormal, the second driving unit narrows a discharge interval of the plurality of charging units and drives the solenoid valve as one ON operation.

According to the above configuration, if the constant current circuit becomes abnormally open, the solenoid valves are not driven for an extremely short time by the single discharge of the charging means, but the discharging of the plurality of charging means is performed. It is performed continuously. In this case, the solenoid valve keeps on due to the continuous discharge of the plurality of charging means, whereby the on time of the solenoid valve per one time can be adjusted (the on time can be prolonged). As a result, even when an abnormality occurs in the constant current circuit, the ON state of the solenoid valve can be maintained at least for a minimum necessary time.

The interval between the discharges by the plurality of charging means may be determined according to the residual magnetic flux of the drive solenoid constituting the solenoid valve. Before turning off), the subsequent discharging means is discharged. In this specification,
The ON state of the solenoid valve means a state in which the solenoid for driving the solenoid valve is energized to drive the solenoid valve.The normally-closed valve is open, and the normally-open valve is closed. Refers to the valve state.

According to the second aspect of the present invention, the second driving means performs the discharging by the preceding charging means at once, and performs the discharging by the subsequent charging means in small steps to maintain the ON state of the solenoid valve. In such a case, when maintaining the ON state of the solenoid valve by discharging the subsequent charging means, it is preferable to gradually increase the ON time of the solenoid valve.

[0010] That is, the solenoid valve usually requires a large amount of energy when transitioning from off to on, and can maintain the on state with relatively little energy after the completion of switching from off to on. Therefore, as described above, by discharging the subsequent charging means little by little after discharging the preceding charging means, the ON state of the solenoid valve can be maintained for a long time. Desirably, at the time of discharging by the subsequent charging means, a current approximately equal to the constant current by the constant current circuit is supplied to the solenoid valve.

In particular, according to the configuration of the third aspect, during the period from the start of the subsequent discharge to the end of the discharge, the necessary energy is always supplied to the solenoid valve, and the on-state is prolonged. That is, the discharging time is shortened at the beginning of discharging when the charging voltage of the charging means (capacitor) is relatively large, and the discharging time is lengthened as the charging voltage decreases.

The invention described in claim 4 is applied to a high-pressure fuel injection control device of a vehicle engine, and performs a main injection and a pilot injection preceding the main injection to a cylinder of the engine. Then, the first drive unit performs the pilot injection and the main injection, respectively, by discharging by the plurality of charging units and subsequently applying a constant current. The second driving means continuously performs the discharging by the plurality of charging means, and performs one fuel injection by the discharging of the charging means. In this case, the minimum required fuel injection amount for the operation of the engine can be secured, and problems such as the engine falling into an extremely low speed operation or engine stall can be avoided.

[0013] In the invention according to claim 5, the abnormality judging means judges the presence or absence of an abnormality based on the output level of the constant current circuit after a predetermined time has elapsed since the discharging of the charging means. In this case, the presence or absence of an abnormality in the constant current circuit can be reliably detected, and the solenoid valve can be appropriately driven.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of the present invention will be described below with reference to the drawings. In the present embodiment, the present invention is embodied as a common rail type fuel injection device for a multi-cylinder diesel engine. Supplied. The solenoid valve is driven by a solenoid valve drive circuit having a constant current circuit and a plurality of charging means (capacitors), and the main injection and the pilot injection preceding the main injection are appropriately performed by opening and closing the solenoid valve. The details of the fuel injection device will be described below.

FIG. 1 shows the overall configuration of a common rail fuel injection system for a diesel engine. The fuel injection device includes a high-pressure pump 1 for pressurizing fuel, a common rail 2 for storing high-pressure fuel pressurized by the high-pressure pump 1, a fuel injection valve 3 for injecting high-pressure fuel from the common rail 2, and a fuel injection control. And an electronic control unit (hereinafter referred to as an ECU) 32 for controlling the operation of the electronic control unit. The fuel injection valve 3 is provided for each cylinder in a multi-cylinder diesel engine.

The ECU 32 comprises a microcomputer (hereinafter referred to as a microcomputer) 4 comprising a logical operation circuit, an electromagnetic valve driving circuit 5 for opening and closing the fuel injection valve 3 according to a command of the microcomputer 4, and a constant flowing through the electromagnetic valve driving circuit 5. A constant current detecting circuit 70 for detecting a current level.

Engine operation information such as an accelerator opening signal, an engine speed signal NE, and a cylinder discrimination signal G is input to the microcomputer 4 from various sensor groups (not shown). The microcomputer 4 calculates an optimal fuel injection amount and fuel injection timing based on various types of engine operation information, and transmits the calculation results to the solenoid valve drive circuit 5 as a solenoid valve drive signal. Further, the microcomputer 4 transmits to the solenoid valve drive circuit 5 a boost permission signal for boosting the battery voltage to a voltage higher than the voltage value and a main injection permission signal for permitting the execution of the main injection.

The solenoid valve driving circuit 5 receives the solenoid valve driving signal and supplies a voltage necessary for driving to the fuel injection valve 3. The solenoid valve 17 of the fuel injection valve 3 (in this embodiment, a three-way solenoid valve) ) Is opened. The constant current detection circuit 70 outputs a constant current detection signal to the microcomputer 4 for determining whether there is an abnormality in the constant current flowing through the current drive circuit 5 (the solenoid valve 17).

In the high-pressure pump 1, a drive shaft 7 is rotatably supported in a housing 6, and the drive shaft 7 is drivingly connected to an output shaft of a diesel engine. A cam 8 is eccentrically fixed to the drive shaft 7, and a piston 9 is urged by a spring 10 on a cam surface (outer peripheral surface) of the cam 8. The piston 9 is slidably supported in the cylinder 11 and the drive shaft 7
By the rotation of the cam 8 accompanying the rotation of, it slides in the vertical direction in the figure. At this time, the fuel tank 12
And the fuel in the cylinder 11 is pressurized with the upward movement of the piston 9, and the pressurized fuel is supplied to the common rail 2 via the check valve 13.

The microcomputer 4 controls the opening and closing of an electromagnetic valve 15 provided in the high-pressure pump 1 while monitoring the fuel pressure in the common rail 2 with a pressure sensor 14 provided in the common rail 2 to store the pressurized fuel in the tank 12. Spill to the side. Thus, the pressure of the fuel in the common rail 2 is maintained at a constant value.

The fuel injection valve 3 includes a fuel injection valve body 16 and a three-way solenoid valve 17. High-pressure fuel from the common rail 2 is supplied to the fuel injection valve body 16 and the three-way solenoid valve 17. In the fuel injection valve main body 16, a needle valve 19 is disposed in the fuel chamber 18. The needle valve 19 is connected to a piston 20 and is urged by a spring 21 in a direction to close the injection port.

The three-way solenoid valve 17 has a housing 22.
An outer valve 23 is supported in the inner hole 22a so as to be slidable up and down. The housing 22 is provided with a first port (fuel intake port) 24, a second port 25, and a drain port 26. The first port 24 is provided on the common rail 2, the second port 25 is provided on a space above the piston 20, The drain ports 26 are connected to drain tanks 27, respectively. The outer valve 23 is provided with a port 28 corresponding to the first port 24 and a port 29 corresponding to the second port 25.

A drive solenoid 30 is provided above the housing 22. Here, the outer valve 23 is urged downward by a spring 31 and the drive solenoid 3
0, the first port 24 of the housing 22
And the port 28 of the outer valve 23 communicate with each other, and the second port 25 of the housing 22 communicates with the port 29 of the outer valve 23. Accordingly, high-pressure fuel from the common rail 2 is applied to the upper surface of the piston 20 through these ports 24, 28, 29, 25 and the inner hole 23a of the outer valve 23, and the needle valve 19 is pressed downward by this pressure, and Is held in a closed state (the state shown).

When the drive solenoid 30 is energized, the outer valve 23 is sucked up, the port 24 is closed, and the ports 25 and 26 communicate with each other. Therefore, the pressure applied to the piston 20 passes through the ports 25 and 26 to the drain tank 27 side ( Leak to the low pressure side). Therefore, the needle valve 19 is raised by the high-pressure fuel in the fuel chamber 18, and the fuel injection valve 3 opens the injection port to inject the fuel.

When the drive solenoid 30 is not energized, the common rail 2 is directed downward with respect to the outer valve 23.
And the urging force of the spring 31 are acting,
In order to connect the ports 25 and 26 to inject high-pressure fuel in the common rail 2, not only is the absorbed energy required to overcome the downward force “F” of the outer valve 23 necessary, but also the operation of sucking the outer valve 23 is performed. If not performed at high speed, the ports 24 and 26 communicate with each other, and fuel escapes to the drain tank 27. Further, in order to precisely control the injection start timing, the suction operation of the outer valve 23 must be performed at an extremely high speed.

Therefore, in order to quickly operate the three-way solenoid valve 17 against the fuel pressure reaching a maximum of 150 MPa, the solenoid valve drive circuit 5 controls the voltage (12 volts or 24 Volts) to drive the solenoid 3 of the three-way solenoid valve 17
Discharge is performed when 0 is applied. The magnetic flux sharply increases due to the sudden rising current accompanying such high-voltage discharge, thereby enabling high response even under a high fuel pressure.

FIG. 2 shows the solenoid valve driving circuit 5 in the ECU 32.
3 is an electric circuit diagram showing a specific configuration of a constant current detection circuit 70. FIG. A primary coil 34a of a transformer 34, a transistor 35 as a boost switching element, and a resistor 36 are connected in series to a battery (a battery terminal 33 in FIG. 2) which is a DC power supply. A diode 37 and a main injection capacitor 38 are connected in series to the secondary coil 34b of the transformer 34. Transformer 3
4, a diode 39 and a pilot injection capacitor 40 are connected in series to the secondary coil 34b.

At a connection point a between the diode 37 and the main injection capacitor 38, a disconnecting circuit 41, a diode 42, and a drive solenoid 30 of the three-way solenoid valve 17 are provided.
And a transistor 43 as a switching element for driving an electromagnetic valve are connected in series. Here, the transistor 43 is provided corresponding to the fuel injection valve 3 (the three-way solenoid valve 17) provided in each cylinder, and the drive solenoid is turned on by turning on the transistor 43 corresponding to each fuel injection valve 3. Current flows through 30. In other words, the solenoid valve drive current I1 is supplied to the drive solenoid 30 of the first cylinder, the solenoid valve drive current I2 is supplied to the drive solenoid 30 of the second cylinder which is the next combustion cylinder, and so on. The solenoid valve drive current In flows through 30.

The disconnecting circuit 41 comprises a transistor 44, a diode 45, a transistor 46, and resistors 47, 48 and 49 as switching devices for disconnection. A transistor 44 is provided between the connection point a and the diode 42.
Is arranged, and a diode 45 is interposed between the gate terminal and the source terminal of the transistor 44. A resistor 47 and a transistor 4 are connected to the gate terminal of the transistor 44.
6 is connected, and a resistor 48 is interposed between the base terminal and the emitter terminal of the transistor 46. The base terminal of the transistor 46 is connected to the microcomputer 4 via a resistor 49.
It is connected to the. Transistor 4 of disconnection circuit 41
4 is turned on / off via a transistor 46 by a main injection permission signal M from the microcomputer 4. When the transistor 44 is off, the main injection capacitor 3
8 and the drive solenoid 30 are electrically disconnected, and when the transistor 44 is in the ON state, the main injection capacitor 38 and the drive solenoid 30 are electrically connected.

At a connection point b between the diode 39 and the pilot injection capacitor 40, a diode 50, a driving solenoid (load) 30 of the three-way solenoid valve 17, and a transistor 43 are connected in series.

The gate terminal of each transistor 43 for driving the solenoid valve is connected to the microcomputer 4 by a drive signal line. Each transistor 43 is turned on by a solenoid valve drive signal T1, T2,..., Tn from the microcomputer 4. A constant current circuit 51 is connected to the battery terminal 33, and a constant current generated by the constant current circuit 51 is supplied to the drive solenoid 30 via a diode 52. Note that 64 in FIG.
Is a diode provided on the ground side in a power supply line to the drive solenoid 30.

On the other hand, a series circuit (voltage dividing circuit) including resistors 53 and 54 is provided for the pilot injection capacitor 40, and a connection point c between the resistors 53 and 54 is connected via a resistor 55 to an inversion of a comparator 56. Connected to input terminal. That is, a signal of a level corresponding to the voltage between the terminals of the pilot injection capacitor 40 is sent to the comparator 56 as a voltage monitoring signal. Further, a constant-voltage power supply 57 is connected to a non-inverting input terminal of the comparator 56, and the comparator 56 compares the level of the voltage monitoring signal with a constant voltage value (corresponding to a boosting end value) from the constant-voltage power supply 57.

The output terminal of the comparator 56 is connected to one input terminal of the AND gate 58. An oscillation circuit 59 is connected to the other input terminal of the AND gate 58,
The oscillating circuit 59 outputs an oscillating signal to the AND gate 58 in response to the boost permission signal from the microcomputer 4. The output terminal of the AND gate 58 is connected to the transistor 6 via the resistor 60.
2 base terminals. A resistor 61 is provided between the base and the emitter of the transistor 62. The collector terminal of the transistor 62 is connected to the battery terminal 33 via the resistor 63, and the collector terminal is connected to the gate terminal of the transistor 35.

Here, the charging operation of the capacitors 38 and 40 will be briefly described. When the fuel injection (main injection) in a certain cylinder ends, the boost permission signal is set to the permission side until the start of fuel injection (start of pilot injection) in the next combustion cylinder. Thus, under the condition that the voltage monitoring signal becomes equal to or lower than the potential of the constant-voltage power supply 57, the transistor 6
2, 35 operate on / off. When the transistor 35 is turned on and off, the secondary coil 34 of the transformer 34 is turned on.
The secondary current flows through b, and charges are charged to the capacitors 38 and 40 through the diodes 37 and 39. At this time, the capacitor 3 is connected to the secondary coil 34b of the transformer 34.
Since the capacitor 8 and the capacitor 40 are connected together, the two capacitors 38 and 40 are charged on the side with less charge, and the capacitors 38 and 40 store substantially the same voltage (equal energy if the capacity is the same). .

On the other hand, when the three-way solenoid valve 17 is driven by the constant current of the constant current circuit 51,
A current level flowing through the drive solenoid 30 is detected, and the detection result is output to the microcomputer 4 as a constant current detection signal DG. That is, in the constant current detection circuit 70, the current detection resistor 71 is connected to the source terminal of each transistor 43 for driving the solenoid valve. The non-inverting input terminal of the comparator 73 is connected to the current detecting resistor 71 via the resistor 72. A constant-voltage power supply 74 is connected to an inverting input terminal of the comparator 73.

The comparator 73 compares a voltage value corresponding to a constant current with a predetermined constant voltage value from the constant voltage power supply 74, and outputs the comparison result to the microcomputer 4. Constant current circuit 51
Is normal, the constant current flowing through the drive solenoid 30 is 3
A [Ampere]. In this case, if the drive current flowing through the drive solenoid 30 is, for example, 1 A [ampere] or more, the comparator 73 outputs the H level constant current detection signal DG. If the drive current flowing through the drive solenoid 30 is less than, for example, 1 A [ampere], the comparator 73 outputs an L level constant current detection signal DG.

Next, the operation of the fuel injection control device configured as described above will be described with reference to FIGS. FIG. 3 is a flowchart showing a fuel injection control routine executed by the microcomputer 4. FIG. 4 is a time chart showing the normal operation of the constant current circuit 51, and FIG. 5 is a time chart showing the normal operation of the constant current circuit 51.

First, the basic operation of the solenoid valve drive circuit 5 in a normal state will be described with reference to FIG. The engine speed signal NE is generated as a pulse signal for each predetermined crank angle. In this embodiment, one revolution of the engine (360 ° C.
A), 48 NE pulses are output for each cylinder. In the case of a four-cylinder engine, each cylinder injection (180 °
NE pulses of “0” to “23” are output for each CA). The cylinder discrimination signal G is output, for example, every two revolutions of the engine.

The drive signals Tn and Tn + 1 for the nth and (n + 1) th cylinder solenoid valves are output based on the pilot injection timing TTP and the main injection timing TTM based on the "0" th NE pulse. The driving signals Tn and Tn + 1 are
It is kept on at the respective injection times TP and TM corresponding to the pilot injection amount QP and the main injection amount QM.

Time t in the figure corresponding to the pilot injection timing
When the drive signal Tn is turned on at 1, the transistor 43 corresponding to the n-th cylinder solenoid valve is turned on. At this time, the main injection permission signal M is off. That is, the transistor 44 of the disconnection circuit is turned off, and the main injection is prohibited. Therefore, at this time t1, the charge of the pilot injection capacitor 40 is discharged at a stretch, and the drive solenoid 30 is energized. At this time, the driving solenoid 3
Even when a large current (peak current) flows to zero and the fuel pressure is high, high-speed response can be realized. That is, when the valve is opened for pilot injection, the valve opening operation is quickly performed by the current from the pilot injection capacitor 40.

After the discharge, a constant current is subsequently supplied to the drive solenoid 30 from the constant current circuit 51. Thus, at the time of fuel injection of the fuel injection valve 3, the valve open state is held by the constant current (hold current) from the constant current circuit 51. Thereafter, when the drive signal Tn is turned off at time t2, the fuel injection by the fuel injection valve 3 is stopped accordingly. Incidentally, the actual fuel injection timing due to the opening of the fuel injection valve 3 is slightly delayed from the drive signal Tn as shown by the hatched area in the figure.

When the drive signal Tn is turned on at time t3 in the figure corresponding to the main injection timing, the transistor 43 corresponding to the n-th cylinder solenoid valve is turned on again. At this time, the main injection permission signal M is turned on. That is, the transistor 44 of the disconnection circuit is turned on, and the main injection is permitted. Therefore, at this time t3, the electric charge of the main injection capacitor 38 is discharged at once, and the drive solenoid 30 is energized. At this time, a high-speed response can be realized even under a high fuel pressure in which a large current (peak current) flows through the drive solenoid 30. That is, when the valve is opened for the main injection, the valve opening operation is promptly performed by the current from the main injection capacitor 38.

After the discharge, similarly to the pilot injection, a constant current is subsequently supplied from the constant current circuit 51 to the drive solenoid 30, and the valve open state is held by the constant current (hold current). Thereafter, when the drive signal Tn is turned off at time t4, the fuel injection by the fuel injection valve 3 is stopped accordingly. At time t4, the main injection permission signal M is turned off.

At time t5 after the end of the main injection, the boost permission signal (not shown) is switched from the inhibition side to the permission side, and
Accordingly, charging of the capacitors 38 and 40 for the main injection and the pilot injection is started. This boost permission signal is switched to the prohibition side at the pilot injection timing of the next combustion cylinder.

FIG. 5 shows a state where, for example, the constant current circuit 51 has an open abnormality. In such a case, after the discharge of the pilot injection capacitor 40 and the discharge of the main injection capacitor 38, the constant current circuit 51 stops flowing due to the abnormality of the constant current circuit 51. That is, the capacitor 4
When a peak current is generated due to the discharge of 0, 38, the hold current cannot flow.

In the case of FIG. 5, the microcomputer 4 outputs two solenoid valve drive signals corresponding to the pilot injection and the main injection as one solenoid valve drive signal. For example, the drive signal Tn for the n-th cylinder solenoid valve is output based on the injection timing TT based on the "0th" NE pulse, and is kept on for an injection time (TP + TM) corresponding to the total injection amount QTL. You.

That is, when the drive signal Tn is turned on at time t11 in the figure, the transistor 43 corresponding to the n-th cylinder solenoid valve is turned on. At this time, the main injection permission signal M is initially turned off. Therefore, at this time t11,
The charge of the pilot injection capacitor 40 is discharged at a stretch, the drive solenoid 30 is energized, and the drive solenoid 3
A large current (peak current) flows through zero. The drive current In of the n-th cylinder solenoid valve reaches a peak current with the discharge of the pilot injection capacitor 40, and then starts decreasing. When the drive current In decreases, the value thereof decreases relatively slowly due to the residual magnetic flux of the solenoid valve 17.

Then, at time t before the closing of the n-th cylinder solenoid valve,
At 12, the main injection permission signal M is output. As a result, the electric charge of the main injection capacitor 38 is discharged at a stretch while the open state of the n-th cylinder solenoid valve is maintained, and a peak current flows through the drive solenoid 30 again. The n-th cylinder solenoid valve is kept open by the residual magnetic flux after the peak current.

Thereafter, when the drive signal Tn is turned off at time t13, the fuel injection by the fuel injection valve 3 is stopped accordingly. As a result, a fuel amount corresponding to the injection time (TP + TM) is injected and supplied to the engine.

The injection timing TT for shifting the drive signal Tn of the n-th cylinder solenoid valve from off to on is desirably substantially equal to the main injection timing TTM in FIG. By setting “TT ≒ TTM”, the combustion torque by the fuel injection can be secured at the fuel injection timing corresponding to the original main injection. The interval between the discharges by the capacitors 38 and 40 may be determined in accordance with the residual magnetic flux of the drive solenoid 30, and before the residual magnetic flux due to the discharge of the previous capacitor disappears (before the electromagnetic valve 17 is turned off), the subsequent interval. To discharge the capacitor.

Next, the fuel injection control routine of FIG. 3 will be described. This routine is started for each fuel injection of each cylinder, and the microcomputer 4 first fetches various sensor information such as an engine speed, an accelerator opening, a fuel injection pressure (common rail pressure) in step 101. Also, the microcomputer 4
In the following step 102, it is determined whether or not the constant current abnormality flag F is "1". The constant current abnormality flag F indicates the presence or absence of an abnormality in the constant current circuit 51. F = 0 indicates no abnormality and F = 1 indicates an abnormality.

If F = 0, the microcomputer 4 proceeds to step 1
03, the pilot injection amount QP, the main injection amount Q
M, pilot injection timing TTP, main injection timing TTM
Is calculated. Each of these values is calculated using a well-known calculation method,
For example, engine speed and accelerator opening (engine load)
Required based on such as. Thereafter, the microcomputer 4 makes the QP, QM, TTP, TTM calculated in step 104
The solenoid valve drive signal Tn is obtained based on the following equation, and this solenoid valve drive signal Tn is output to the solenoid valve drive circuit 5 (transistor 43). At this time, the solenoid valve drive signal Tn is composed of a pilot injection signal (t1 to t2 in FIG. 4) and a main injection signal (t3 to t4 in FIG. 4).

Thereafter, the microcomputer 4 sets the constant current detection circuit 7
It is determined whether the constant current detection signal DG taken from 0 is at the H level. Specifically, the output level of the constant current detection circuit 70 after 500 μs from the output of the solenoid valve drive signal Tn (rising of Tn) is determined. The timing 500 μs after the rise of Tn corresponds to the timing at which the peak current due to the discharge of the capacitors 38 and 40 stops and a predetermined constant current should flow from the constant current circuit 51 (the peak current is about 300 μs after the output of Tn). Flows between them).

In this case, if the constant current circuit 51 is normal, the DG signal 500 μs after the output of Tn becomes “H”, and the microcomputer 4 once terminates this routine.
If a predetermined constant current does not flow 500 μs after the output of Tn and the constant current circuit 51 is abnormal, the DG signal becomes “L”.
Becomes In this case, the microcomputer 4 proceeds to step 106, sets “1” to the constant current abnormality flag F, and ends this routine.

When "1" is set to the constant current abnormality flag F, the affirmative determination is made every step 102 thereafter. Therefore, the microcomputer 4 calculates the fuel injection amount (total injection amount QTL) for one injection by the continuous discharge of the capacitors 38 and 40 and the injection timing TT in step 107.
In this case, the maximum amount of fuel injection by only the capacitors 38 and 40 is limited. Therefore, for example, the total injection amount QTL according to the accelerator opening (engine load) is calculated according to the relationship in FIG.

Thereafter, the microcomputer 4 obtains the solenoid valve drive signal Tn based on the calculated total injection amount QTL and the injection timing TT in step 108, and sends the solenoid valve drive signal Tn to the solenoid valve drive circuit 5 (transistor 43). Output. In this embodiment, the rise 30 of the solenoid valve drive signal Tn
It is set so that the fuel injection corresponding to the main injection is started after 0 μs. That is, the main injection permission signal M is turned on 300 μs after the rise of the solenoid valve drive signal Tn. At this time, the solenoid valve drive signal Tn is
The pilot injection signal and the main injection signal are combined (t11 to t13 in FIG. 5).

In the present embodiment, the steps 103 and 104 in FIG. 3 correspond to first driving means, and the steps 107 and 108 correspond to second driving means. Step 106 corresponds to abnormality determination means.

According to the above-described embodiment, the following effects can be obtained. (A) In the present embodiment, it is determined whether or not there is an abnormality in the constant current circuit 51. If there is an abnormality, the interval between discharges of the two capacitors 40 and 38 for pilot injection and main injection is narrowed. The solenoid valve 17 is driven as one ON operation. That is, discharging by the capacitors 38 and 40 is continuously performed, and the capacitors 38 and 40 are discharged.
, One fuel injection is performed.

According to the above configuration, if the constant current circuit 51 becomes abnormally open, the solenoid valves are not driven for an extremely short time by one-time discharge of the capacitors 38, 40, but the capacitors 38, 40 are driven. The on time of the solenoid valve 17 can be prolonged by performing the discharge continuously. As a result, even when an abnormality occurs in the constant current circuit 51, the ON state of the solenoid valve 17 can be maintained in at least a minimum necessary time, and a required fuel injection amount can be secured. In this case, the minimum required fuel injection amount for the operation of the engine can be secured, and problems such as the engine falling into an extremely low speed operation or engine stall can be avoided.

(B) After a predetermined time has elapsed from the start of discharging of the capacitors 38 and 40, the presence or absence of an abnormality is determined based on the output level of the constant current circuit 51. in this case,
Abnormality of the constant current circuit 51 can be reliably detected, and the solenoid valve 17 can be appropriately driven.

(C) Since the transformer 34, the transistor 35 and the oscillation circuit 59 for charging the two capacitors 38 and 40 have a single structure, the solenoid valve 17 can be driven at a high speed while simplifying the structure. Becomes

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. However, in the configuration of the second embodiment, the same components as those of the above-described first embodiment are denoted by the same reference numerals and the description thereof is simplified. And below is the first
The following description focuses on the differences from this embodiment.

FIG. 7 is a time chart showing an outline of the operation of the solenoid valve drive circuit 5 in the present embodiment, and FIG. 7 shows the operation of the constant current circuit 51 when it is abnormal (the normal operation is It is omitted because it is the same as FIG. 4).

In FIG. 7, the microcomputer 4 outputs two solenoid valve drive signals corresponding to the pilot injection and the main injection as one solenoid valve drive signal. For example, the drive signal Tn for the n-th cylinder solenoid valve is output based on the injection timing TT based on the “No. 0” NE pulse, and is kept on for an injection time corresponding to the total injection amount QTL. The injection timing TT substantially coincides with the main injection timing TTM in FIG. 4, as in FIG.

That is, when the drive signal Tn is turned on at time t21 in the figure, the transistor 43 corresponding to the n-th cylinder solenoid valve is turned on. At this time, the main injection permission signal M is initially turned off. Therefore, at this time t21,
The charge of the pilot injection capacitor 40 is discharged at a stretch, the drive solenoid 30 is energized, and the drive solenoid 3
A large current (peak current) flows through zero.

Then, at time t22 (for example, from t21 to 3)
After 00 μs), the main injection permission signal M is output. The main injection permission signal M is a signal that is repeatedly turned on and off little by little, and the charging voltage of the main injection capacitor 38 gradually decreases during a period from time t22 to t23. At this time, the on-time (discharge time) is shortened at the beginning of the discharge in which the charging voltage of the main injection capacitor 38 is relatively large, and the on-time is increased as the charging voltage decreases. However, the off time may be constant.

The drive current In for the n-th cylinder solenoid valve is at time t
After reaching the peak current due to the discharge of the pilot injection capacitor 40 at 21, it starts to decrease. And time t
During the ON / OFF period of the main injection permission signal M from 22 to t23, the drive current In is held at a substantially constant current value. Therefore, during the period from time t21 to time t23, the n-th
The open state of the cylinder solenoid valve is maintained. Here, the drive current In from the time t22 to t23 is
The on / off time of the main injection permission signal M is adjusted so that the value becomes approximately the same as the constant current of 1.

The processing of the microcomputer 4 for realizing the operation of FIG. 7 is almost the same as that of FIG. 3 except that the content of step 108 in FIG. 3 is partially changed. It is. Therefore, although not shown here, as a general outline, the microcomputer 4 obtains the solenoid valve drive signal Tn corresponding to the total injection amount QTL and the injection timing TT in step 108 and outputs the signal to the solenoid valve drive circuit 5. At the same time, it outputs a command to turn on / off the main injection permission signal M.

According to the present embodiment, as in the first embodiment, even when an abnormality occurs in the constant current circuit 51, the ON state of the solenoid valve 17 can be maintained in at least the minimum necessary time. The required fuel injection amount can be secured. Further, in the present embodiment, the pilot injection capacitor 40
Discharging by the (previous charging means) is performed at once, and discharging by the main injection capacitor 38 (subsequent charging means) is performed in small steps, so that the ON state of the solenoid valve 17 is maintained. That is, the solenoid valve 17 normally requires a large amount of energy when shifting from off to on, and can maintain the on state with relatively little energy after the completion of switching from off to on. Therefore, as described above, after the capacitor 40 is discharged, the subsequent capacitor 38 is discharged little by little, so that the ON state of the solenoid valve 17 can be maintained for a long time.

Further, at the time of discharging by the main injection capacitor 38, the on-time of the solenoid valve 17 is gradually increased. Therefore, during the period from the start of discharging of the capacitor 38 to the end of discharging, only a necessary amount of energy is always supplied to the solenoid valve 17, and the on-state of the solenoid valve 17 is prolonged.

The embodiment of the present invention can be realized in the following modes other than the above. When an abnormality occurs in the constant current circuit 51, the interval between the discharge of the pilot injection capacitor 40 and the discharge of the main injection capacitor 38 is variably set according to the engine operating state such as the common rail pressure. In such a case, if the intervals between the discharges by the capacitors 38 and 40 are increased according to the engine operating state, the combustion torque can be increased even when an abnormality occurs.

In the second embodiment, the constant current circuit 5
1, the pilot injection capacitor 40
The discharge of the main injection capacitor 38 following the discharge of the capacitor 38 is performed in small increments, and the ON time (discharge time) of the capacitor 38 is set variably. At this time, the ON time of the capacitor 38 is controlled by feedback control based on the drive current. May be. In such a case, a configuration for detecting the drive current and taking the detection result into the microcomputer 4 is added. And
The feedback amount is calculated so that the drive current matches the constant current of the constant current circuit 51, and the ON time of the capacitor 38 is set according to the calculation result. Further, the configuration may be simplified by setting the ON time of the capacitor 38 to a constant value.

In each of the above embodiments, the solenoid valve drive circuit 5 is constituted by using two capacitors 38 and 40 for main injection and pilot injection as a plurality of charging means.
It is also possible to configure the solenoid valve drive circuit 5 using three or more capacitors. For example, the above two capacitors 3
In addition to 8, 40, a capacitor for post-injection performed after the main injection is provided. When an abnormality occurs in the constant current circuit 51, the three capacitors are continuously discharged to perform one fuel injection. Incidentally, the post-injection is performed to use the fuel (HC component) as a reducing agent for the catalyst, and injects an amount of fuel corresponding to the NOx generation amount predicted from the engine speed and the load.

The electromagnetic valve driving device of the present invention can be embodied as a driving device for an electromagnetic valve in a high-pressure pump or as a driving device for an electromagnetic spill valve in a distribution type fuel injection pump. In the above embodiment, the solenoid valve (three-way solenoid valve 17) is embodied as a normally closed valve, but may be embodied as a normally open valve instead.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing an outline of a common rail fuel injection device for a diesel engine according to an embodiment of the invention.

FIG. 2 is an electric circuit diagram showing a solenoid valve driving circuit.

FIG. 3 is a flowchart showing a fuel injection control routine.

FIG. 4 is a time chart for explaining the operation of the solenoid valve drive circuit.

FIG. 5 is a time chart for explaining the operation of the solenoid valve drive circuit.

FIG. 6 is a diagram for setting the total injection amount when the constant current circuit is abnormal.

FIG. 7 is a time chart for explaining the operation of the solenoid valve drive circuit in the second embodiment.

[Explanation of symbols]

Reference numeral 3 denotes a fuel injection valve, 4 denotes a first drive unit, a second drive unit, a microcomputer (microcomputer) serving as an abnormality determination unit, 5 a solenoid valve drive circuit, 17 a three-way solenoid valve, 38
... Main injection capacitor constituting charging means, 40 ...
Pilot injection capacitor constituting charging means, 51
... constant current circuit, 70 ... constant current detection circuit.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01F 7/18 H01F 7/18 K // F02M 45/10 F02M 45/10 47/00 47/00 EF

Claims (5)

[Claims] A constant current circuit for generating a predetermined constant current from a power supply voltage; and a plurality of charging means for storing a voltage higher than the power supply voltage. A solenoid valve driving device that discharges at a stretch and continuously maintains the on state of the solenoid valve by the constant current of the constant current circuit, wherein the plurality of charging means discharges a high voltage to drive the solenoid valve at predetermined intervals. First driving means for causing the constant current circuit to determine whether there is an abnormality, and determining that the constant current circuit is abnormal, by narrowing an interval of discharge by the plurality of charging means for one time. And a second driving means for driving the solenoid valve as an ON operation of the solenoid valve. 2. The solenoid valve according to claim 1, wherein said second drive means discharges said first charging means at a stroke and discharges said succeeding charging means in small steps to maintain an ON state of said solenoid valve. Drive. 3. The electromagnetic valve driving device according to claim 2, wherein the on-time of the electromagnetic valve is gradually increased when the on-state of the electromagnetic valve is maintained by discharging by the subsequent charging means. Drive. 4. A high-pressure fuel injection control device for a vehicle engine, wherein fuel is supplied from a fuel injection valve to an engine by driving an electromagnetic valve. An electromagnetic valve driving device for performing a pilot injection preceding the pilot valve, wherein the first driving unit individually performs the pilot injection and the main injection by discharging the plurality of charging units and applying a constant current thereafter. The second driving unit is configured to continuously perform discharge by the plurality of charging units and perform one fuel injection by discharging the charging units. A solenoid valve driving device according to any one of the above. 5. The apparatus according to claim 1, wherein said abnormality determining means determines whether or not there is an abnormality based on an output level of said constant current circuit after a predetermined time has elapsed from said discharging of said charging means. The electromagnetic valve driving device as described in the above.