JP2000345898A - Solenoid valve driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solenoid valve driving device having a simple structure and capable of stably performing the valve opening operation at high speed. SOLUTION: A monostable signal from a monostable circuit 51 is input into a flip-flop circuit 50. The set state of the flip-flop circuit 50 and the reset state are switched each time an ON-signal from the monostable circuit 51 is input, and simultaneously, an input signal boosted through a drive circuit 41 or 42 of either base of a MOS transistor HS1 as a discharge switching element of a first drive condenser C1 or a MOS transistor HS2 as a discharge switching element of a second drive condenser C2 is turned on. Therefore, either the first drive condenser C1 or the second drive condenser C2 is discharged, and the large current is supplied to a common circuit 300.

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 fuel injection control device for a diesel engine which performs pilot injection prior to main injection.

[0002]

2. Description of the Related Art In a fuel injection control device for a diesel engine, fuel is injected twice from a fuel injection valve (injector) during one cycle of intake, compression, explosion, and exhaust to reduce engine noise and reduce exhaust gas quality. Has been improved. The two injections are a pilot injection that explodes a fire in the cylinder with a small amount of injection, and a main injection corresponding to the amount of fuel required for the original work. In the main injection, fuel burns following the pilot injection. Such combustion suppresses rapid combustion in one cycle, thereby realizing reduction of explosion sound and nitrogen oxides (NOx) during combustion. However, it is necessary to operate the fuel injection valve at a high speed in order to achieve injection in one cycle having such a very short time, and further, injection at a high pressure.

As a method of driving a fuel injection valve, that is, an electromagnetic valve at a high speed, there is a method of discharging energy previously charged in a capacitor to a drive solenoid of the electromagnetic valve at the timing of operating the electromagnetic valve. This is because the magnetic flux (=
Since the rise of force) is too slow to control, the high voltage that is higher than the battery voltage is stored in the capacitor, the drive solenoid discharges from the capacitor, and the magnetic flux rises rapidly to open the solenoid valve at high speed. It is. In more detail, in the fuel injection control device, the interval between the pilot and the main injection may be reduced to about 0.1 msec, so that the charging of the capacitor used for the main injection is completed after the capacitor used for driving the pilot injection is released. Since it is difficult to keep time, it is necessary to prepare two pilot capacitors and a main capacitor as charging capacitors, use the energy of the two charging capacitors during one cycle, and re-use it by the next cycle of fuel injection. Complete charging.

[0004]

However, in the above-described conventional solenoid valve driving device, a capacitor for supplying a current necessary for opening the solenoid valve and a circuit such as a DC-DC converter for charging the capacitor are provided. Must be provided for the pilot injection and the main injection, respectively. Especially D
Since the C-DC converter includes an inductor for boosting the voltage, there is a problem in that providing two of them increases the size of the entire driving device. In addition, since the pilot injection is performed only when the engine is running at low and medium speeds, the load is biased only to the DC-DC converter for main injection and the driving capacitor at the time of high speed rotation in the above-described drive device, and the life of the main injection components May be shorter.

In order to solve such a problem, as shown in Japanese Patent No. 2598595, it is conceivable to use a single drive capacitor. In this case, however, an extremely short drive capacitor between the pilot injection and the main injection is used. Since the drive capacitor must be charged in time, a large load is instantaneously applied to the drive capacitor, thereby deteriorating operation stability and component life. Accordingly, an object of the present invention is to provide an electromagnetic valve driving device capable of performing a high-speed valve opening operation stably with a simple configuration.

[0006]

According to the solenoid valve driving device of the present invention, the charging means having one inductor for charging a plurality of driving capacitors and the driving capacitor for discharging are provided one by one. And a selection circuit for selecting in order. Usually, only one inductor is required for the charging means provided for each capacitor to be charged, so that the size of the device can be reduced. In addition, since one drive capacitor that discharges from the plurality of charged drive capacitors is selected, a large current can be continuously supplied from the plurality of drive capacitors in a short time, and a plurality of electromagnetic waves can be supplied at short time intervals. The valve can be opened and closed. In particular, the present invention is suitable for controlling a fuel injection device used for an engine that performs a plurality of injections. Further, since the plurality of drive capacitors are sequentially discharged one by one, even when only the main injection is performed, the respective drive capacitors are used equally, and the difference in component life can be reduced.

According to the solenoid valve driving device of the second aspect of the present invention, two driving capacitors are provided, and the selection circuit is provided with two driving capacitors.
A discharge switching element connected to each of the two drive capacitors; and a flip-flop circuit connected to the discharge switching element. Therefore, the two driving capacitors can be alternately selected and discharged. When applied to solenoid valve control of a fuel injection device used for an engine that performs pilot injection and main injection, the two drive capacitors are used equally even if the operation state in which only main injection is continued.

According to a third aspect of the present invention, there is provided a solenoid valve driving device including a means for sequentially selecting driving capacitors to be discharged one by one. Therefore, the charging can be performed in order from the discharged driving capacitor, and the charging is completed in a short time. Therefore, the interval between discharges, that is, the interval between valve opening times can be shortened.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a plurality of embodiments in which the solenoid valve driving device of the present invention is applied to a fuel injection control device for a multi-cylinder diesel engine will be described with reference to the drawings. (First Embodiment) FIG. 1 shows the overall configuration of a fuel injection control device for a diesel engine. A fuel injection control device for a diesel engine includes a pump 1 for pressurizing fuel, a pump 1
A common rail 2 for storing the high-pressure fuel pressurized by the fuel injector, an injector 3 as a fuel injection valve for injecting the high-pressure fuel from the common rail 2, a microcomputer (microcomputer) 4, and the opening and closing drive of the injector 3 according to a command from the microcomputer 4. And a solenoid valve driving circuit 5. The injector 3 is provided for each cylinder of the multi-cylinder diesel engine. An electronic control unit (ECU) 32 is provided by the microcomputer 4 and the solenoid valve driving circuit 5.
Is composed.

In the 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 in contact with a cam surface (outer peripheral surface) of the cam 8 by a spring 10. The piston 9 is slidably supported in the cylinder 11 and slides up and down by rotation of the cam 8 accompanying rotation of the drive shaft 7. At this time, the fuel is introduced from the fuel tank 12 into the cylinder 11 by the downward movement of the piston 9, and the fuel in the cylinder 11 is pressurized by the upward movement of the piston 9, and the pressurized fuel is checked. It is supplied to the common rail 2 via a valve 13. Further, the microcomputer 4 controls the opening and closing of the solenoid valve 15 provided on the pump 1 by monitoring the fuel pressure in the common rail 2 with the pressure sensor 14 provided on the common rail 2 and sends the pressurized fuel to the tank 12 side. By spilling, the pressure of the fuel in the common rail 2 is kept constant.

The injector 3 comprises a fuel injection valve body 16 and a three-way solenoid valve 17, and high-pressure fuel from the common rail 2 is supplied to the fuel injection valve body 16 and the three-way solenoid valve 17. The fuel injection valve body 16 is provided in the fuel chamber 1
A needle valve 19 is disposed in the needle valve 8.
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 and an outer valve 23 in an internal hole 22a.
Are slidably supported up and down. A first port (fuel intake port) 24 and a second port 2
5, a drain port 26 is provided. The first port 24 is the common rail 2 and the second port 25 is the piston 2
0 and the drain port 26 are connected to the drain tank 27, respectively. The outer valve 23 has a port 28 corresponding to the first port 24 and a second port 2
5 are provided.

A drive solenoid 30 is provided above the housing 22. When the drive solenoid 30 is not energized, the outer valve 23 is
Is urged downward, so that the first port 24 of the housing 22 communicates with the port 28 of the outer valve 23, and the second port 25 of the housing 22 communicates with the port 29 of the outer valve 23. Therefore, high-pressure fuel from the common rail 2 is supplied to the piston 20 through these ports 24, 28, 29, 25 and the inner hole 23 a of the outer valve 23.
The needle valve 19 is pressed downward by this pressure to close the injection port.

When the drive solenoid 30 is energized,
The outer valve 23 is sucked and rises to close the port 24, and the port 25 and the port 26 communicate with each other.
Is leaked to the drain tank 27 side (low pressure side) through the port 25 and the port 26. Therefore, the needle valve 19 is raised by the high-pressure fuel in the fuel chamber 18 and opens the injection port to inject the fuel.

When the drive solenoid 30 is not energized, the high-pressure fuel from the common rail 2 and the urging force of the spring 31 act downward on the outer valve 23, and the ports 25 and 26 communicate with each other so that the port 25 and the port 26 communicate with each other. In order to inject high-pressure fuel, the downward force F of the outer valve 23 is required.
Not only is it necessary to absorb absorbed energy to overcome the above problem, but if the operation of sucking the outer valve 23 is not performed at a high speed, the port 24 and the port 26 communicate with each other, and the 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 high fuel pressure, the solenoid valve drive circuit 5
As a result, the battery voltage (12
Volts or 24 volts), and discharges when the drive solenoid 30 of the three-way solenoid valve 17 is energized to supply a high voltage to the three-way solenoid valve 17. The magnetic flux rapidly increases due to the sudden rising current accompanying the supply of such a high voltage, thereby enabling a high response even under a high fuel pressure.

FIG. 2 shows a specific configuration of the solenoid valve driving circuit 5 in the first embodiment. Battery 3 which is a DC power supply
3 includes an inductor 34a of the DC-DC converter 34 as a charging unit and an M as a boosting switching element.
The OS transistor 35 and the resistor 36 are connected in series. The first between the inductor 34a and the transistor
And the second diode D2 are connected in parallel. Further, a first driving capacitor C1 is connected in series to the first diode D1, and a second driving capacitor C2 is connected in series to the second diode D2.

Outputs from the current detection circuit 38, the charging voltage detection circuit 39, and the monostable circuit 51 are input to the DC-DC stop logic circuit 40. When all inputs are off, the DC-DC drive 37 outputs The signal that is boosted and input to the gate of the MOS transistor 35 is turned on, and the inductor 34a is energized.

When a current equal to or more than a predetermined value is detected by the current detection circuit 38, the output from the DC-DC drive 37 is turned off, and the current supply to the inductor 34a is stopped. When the current supply to the inductor 34a is stopped, no current is detected by the current detection circuit 38, whereby the output from the DC-DC drive 37 is turned on again, and the inductor 34a is turned off.
Is energized. The first drive capacitor C1 and the second drive capacitor C2 are charged by repeating the on / off of the current supply to the inductor 34a as described above.

When the charging voltage detecting circuit 39 detects that the voltages of the first driving capacitor C1 and the second driving capacitor C2 have exceeded a predetermined value and the charging has been completed, the output from the DC-DC drive 37 is output. Turns off,
Power supply to the inductor 34a is stopped. Monostable circuit 51
When the output from is turned on, since the first drive capacitor C1 and the second drive capacitor C2 are being discharged, the current supply to the inductor 34a is stopped to stop charging.

The flip-flop circuit 50 receives a monostable signal from a monostable circuit 51. Each time an ON signal is input from the monostable circuit 51, the flip-flop circuit 5
0 is switched between the set state and the reset state, and at the same time, the base of one of the MOS transistor HS1 as the discharge switching element of the first drive capacitor C1 and the MOS transistor HS2 as the discharge switching element of the second drive capacitor C2 The input signal which has been boosted via the drive circuit 41 or 42 is turned on. As a result, one of the first drive capacitor C1 and the second drive capacitor C2 is discharged, and a large current is supplied to the common circuit 300. The flip-flop circuit 50 and the MOS transistors HS1 and HS2 form a selection circuit described in claims.

At this time, the injector 300 is connected to the injector drive MOS transistors 43, 44, 45 provided corresponding to the injectors of the respective cylinders.
46 is determined by ON and OFF. The drive solenoid 30 shown in FIG. 1 is shown in FIG. 2 as one drive solenoid 301, 302, 303, 304 for each of the four cylinders.

The microcomputer 4 receives an accelerator opening signal, an engine speed signal, a water temperature signal, and the like, and detects the operating state of the diesel engine based on these signals. Drive signals Ijt1 to Ijt4 are output from the microcomputer 4 corresponding to the four-cylinder injectors in accordance with the operating state of the engine, shaped by waveform shaping circuits 63 to 66, and driven circuits 53 to 56.
As a switching element for driving the solenoid valve
Input to the gates of OS transistors 43-46.

FIG. 3 is a time chart showing signals when pilot injection and main injection are performed twice in one cycle in each cylinder. A combined injection signal obtained by combining Ijt1 to Ijt4 by an OR circuit is a monostable circuit. The monostable signal input to the mono-stable circuit 51 and output from the monostable circuit 51 is supplied to the flip-flop circuit 50 and the DC-DC stop logic 40.
Is input to

Hereinafter, changes in the voltages of the capacitors C1 and C2 caused by the injector drive signal Ijt1 for performing the pilot injection and the main injection will be described with reference to FIG. First, from a state in which C1 and C2 are charged together sufficiently, the input to the gate of the MOS transistor HS1 at the rising edge of T ₁₁ of the monostable signal corresponding to the pilot injection is on, the input to the gate of the MOS transistor HS2 It turns off, and current is discharged from the first drive capacitor C1 to the drive solenoid 301, and the voltage of C1 decreases.

After the first drive capacitor C1 is discharged, the constant current control circuit 70 and the constant current drive transistor Tr
, A substantially constant current is supplied to the drive solenoid 301, and the injector is kept in the valve-open state while the injector drive signal Ijt1 is on. When the monostable signal is turned off, the input to the gate of the MOS transistor 35 is turned on, and charging of the drive capacitor C1 is started.

[0026] Then, at a timing T ₁₂ of the rise of the monostable signal corresponding to the main injection, the input to the gate of the MOS transistor HS1 is OFF, the MOS transistor H
The input to the gate of S2 is turned on, and the driving capacitor C
2, the current is discharged, and the voltage of C2 decreases.

After the second drive capacitor C2 is discharged, a substantially constant current is supplied to the drive solenoid 301 by the constant current control circuit 70 and the constant current drive transistor Tr, as in the case of the pilot injection, and the injector drive signal is generated. While Ijt1 is on, the injector remains open. When the monostable signal is turned off, the input to the gate of the MOS transistor 35 is turned on. Here, since the first drive capacitor C1 and the second drive capacitor C2 are connected in parallel, one of the lower drive voltage (here, C1
Only 2) is charged. Voltage of C2 rises and the timing T ₁₃ C1 and the C2 will be the same voltage, until T ₁₃ of the completion of charging two driving capacitors C1, C2 is charged evenly. Rise timing T ₁₅ of the next injector drive signal Ijt4, the charging of both the drive capacitor is set so that after the completion. Hereinafter, similar operations are repeated for injector drive signals Ijt4, Ijt3, and Ijt2.

According to this embodiment, the number of inductors required for the charging means and usually provided for each driving capacitor to be charged and requiring a large volume can be reduced to one. The physique can be reduced.

In FIG. 3, the pilot injection and the main injection are performed.
The time chart for the case of
At time, as shown in FIG.
The ejector drive signals Ijt1 to Ijt4 are
Only one main injection signal is provided. In this case, I
jt1 and Ijt3 rising timing T_{twenty one}, T_{twenty three}
Discharges the first drive capacitor C1, and outputs Ijt4 and Ijt4.
jt2 rising timing T _{twenty two}, T_{twenty four}The second drive
The dynamic capacitor C2 is discharged and the two drive capacitors C
1 and C2 can be discharged alternately. That
Therefore, only the main injection is performed, such as when the engine is running at high speed.
Drive capacitors are used equally even when
The difference in component life can be reduced.

(Second Embodiment) FIG. 5 shows a solenoid valve driving circuit 5 according to a second embodiment of the present invention. The portion for outputting the drive signals Ijt1 to Ijt4 from the microcomputer 4 to the injector drive MOS transistors 43 to 46 and the monostable circuit 51 is the same as that of the first embodiment, and is not shown in FIG.

In the second embodiment, the first drive capacitor C
Separate charging voltage detection circuits 391 and 392 are connected to the first and second drive capacitors C2, and their output signals are input to the flip-flop circuit 501. When the charging of the driving capacitor C1 or C2 is completed, the charging voltage detection circuit 3
Each time the signal from 91 or 392 switches from off to on, the flip-flop circuit 501 switches between the set state and the reset state. The input signal boosted via the drive circuit 81 or 82 to one of the bases of the MOS transistor CS2 as a charge switching element of the drive capacitor C2 is turned on. This allows
Only one of the first drive capacitor C1 and the second drive capacitor C2 can be charged.

Hereinafter, in the second embodiment, changes in the voltages of the capacitors C1 and C2 caused by the injector drive signal Ijt1 for performing the pilot injection and the main injection will be described with reference to FIG.

Firstly, from a state in which C1 and C2 are charged together well, at the timing T ₃₁ of the rise of the monostable signal corresponding to the pilot injection, the current from the first driving capacitor C1 is discharged to drive the solenoid 301 C1
Voltage decreases.

After the first drive capacitor C1 is discharged, the constant current control circuit 70 and the constant current drive transistor Tr
, A substantially constant current is supplied to the drive solenoid 301, and the injector is kept in the valve-open state while the injector drive signal Ijt1 is on. Further, the input to the gate of the MOS transistor CS1 is on, the input to the gate of the MOS transistor CS2 is off, and the charging of the drive capacitor C1 is started.

Next, the rise timing T ₃₂ of the monostable signal corresponding to the main injection, drive capacitor C2
, A current is discharged, and the voltage of C2 decreases. After the second drive capacitor C2 is discharged, a substantially constant current is supplied to the drive solenoid 301 by the constant current control circuit 70 and the constant current drive transistor Tr as in the case of the pilot injection, and the injector drive signal Ijt1 is turned on. During this time, the injector remains open. Here, since the input to the gate of the MOS transistor CS1 is on and the input to the gate of the MOS transistor CS2 is off, only the first drive capacitor C1 is charged.

[0036] When the charging of C1 is to complete T _33, 39
The signal input from 1 to the flip-flop circuit 501 changes from off to on, the input to the gate of the MOS transistor CS1 turns off, the input to the gate of the MOS transistor CS2 turns on, and the charging of the drive capacitor C2 starts. .

In the second embodiment, when charging of one of the two drive capacitors is started, charging of the other is started after the charging is completed. Therefore, it is possible to charge one capacitor in a shorter time than charging both capacitors simultaneously, shortening the time interval from T ₃₂ performing the second time discharge to T ₃₄ to perform third round of discharge that Can be. Further, in the second embodiment using the circuit shown in FIG. 5, the charging time can be shortened because one driving capacitor can charge the other driving capacitor even during discharging.

(Third Embodiment) FIG. 7 shows a solenoid valve driving circuit 5 according to a third embodiment of the present invention. Components that are substantially the same as those in the first and second embodiments are given the same reference numerals, and descriptions thereof are omitted. In the circuit of the third embodiment, the MOS transistor CS1 as the charging switching element of the first driving capacitor C1 and the MOS transistor CS2 as the charging switching element of the second driving capacitor C2 are grounded. An output signal from the amplifier can be input to the bases of the drive transistors CS1 and CS2 to turn on / off the transistors. The drive circuit for boosting used in the second embodiment is not required, and the circuit structure is simplified. Can be Also, the third
In the embodiment, the monostable signal from the monostable circuit 51 is DC-
It is necessary to input the signal to the DC stop logic circuit so that one drive capacitor is not charged while the other drive capacitor is discharging.

In the above embodiments of the present invention, two drive capacitors have been described. However, the same effect can be obtained by using three or more drive capacitors. Further, the present invention can be applied not only to a fuel injection control device for a diesel engine, but also to a solenoid valve drive device that performs a valve opening operation continuously in a short time.

[Brief description of the drawings]

FIG. 1 is a diagram showing a fuel injection control device for a diesel engine using an electromagnetic valve driving device according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a solenoid valve driving circuit according to a first embodiment of the present invention.

FIG. 3 is a time chart showing a relationship between an injector drive signal and a capacitor voltage according to the first embodiment of the present invention.

FIG. 4 is a time chart showing a relationship between an injector drive signal and a capacitor voltage according to the first embodiment of the present invention.

FIG. 5 is a circuit diagram showing a solenoid valve driving circuit according to a second embodiment of the present invention.

FIG. 6 is a time chart showing a relationship between an injector drive signal and a capacitor voltage according to a second embodiment of the present invention.

FIG. 7 is a circuit diagram showing a solenoid valve driving circuit according to a third embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 30 drive solenoid 33 battery 34 DC-DC converter (charging means) 34a inductor 35 MOS transistor 50 flip-flop circuit C1 first drive capacitor C2 second drive capacitor HS1 MOS transistor (discharge switching element) HS2 MOS transistor (discharge switching element) Ijt1 to Ijt4 Injector drive signal

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) F02M 51/00 F02M 51/00 F 51/06 51/06 M // F16K 31/06 310 F16K 31/06 310A F term (Reference) 3G066 AA07 AC09 AD02 BA19 BA46 CB12 CC05U CD26 CE22 CE29 DA04 DA09 DC04 DC14 DC18 3G301 HA02 JA14 JA18 LB13 LC10 MA23 MA26 PB08Z PE01Z PE08Z PF03Z PG02Z 3H106 DA07 DA13 DA23 DB02 DB12 DB23 DB32 DC02 FB04

Claims (3)

[Claims] An electromagnetic valve that opens when a drive solenoid is energized; a plurality of drive capacitors that supply current to the drive solenoid; a charging unit having one inductor that charges the plurality of drive capacitors; And a selection circuit for sequentially selecting one drive capacitor at a time. 2. The method according to claim 1, wherein the two drive capacitors are provided, and the selection circuit includes a discharge switching element connected to each of the two drive capacitors, and a flip-flop circuit connected to the discharge switching element. The electromagnetic valve driving device according to claim 1, wherein 3. The solenoid valve driving device according to claim 1, further comprising means for sequentially selecting driving capacitors to be charged one by one.