JPH1162677A - Solenoid valve drive - Google Patents

Abstract

(57) [Problem] To appropriately perform continuous operation of an electromagnetic valve using a single charging circuit. An electromagnetic valve drive circuit includes a constant current circuit for generating a predetermined constant current from a power supply voltage, and a charge circuit having a capacitor for storing a voltage higher than the power supply voltage. The solenoid valve 17 provided on the fuel injection valve that supplies fuel to the diesel engine is connected to the constant current circuit 41 and the charge circuit 33, and is driven by energization of the solenoid coil 30. The solenoid valve 17 (fuel injection valve) is
And the main injection and the pilot injection preceding it are performed at a short time interval shorter than the charging completion time. In this case, during the pilot injection, the charge circuit
The solenoid valve 17 is driven only by the constant current circuit 41 by prohibiting the energization of the solenoid coil 30 by 33, and at the time of the main injection, the energization of the solenoid coil 30 by the charge circuit 33 is permitted and the charge circuit 33 and the constant current circuit 41 To drive the electromagnetic valve 17.

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 relatively short time interval applied to a fuel injection device of an internal combustion engine (diesel engine) for performing main injection or pilot injection preceding it. The present invention relates to an electromagnetic valve driving device for continuously driving an electromagnetic valve.

[0002]

2. Description of the Related Art As is well known, a solenoid valve opens and closes a valve body by using an electromagnetic attraction force generated when a solenoid coil is energized. For example, when high responsiveness is required, such as when applied to a device, a device is applied to increase the valve opening speed by applying a high current at the beginning of energization.

A common rail fuel injection device for a diesel engine will be described as an example. In the fuel injection device, fuel is injected from a fuel injection valve a plurality of times during one cycle of intake, compression, explosion, and exhaust. This has reduced engine noise and improved exhaust emissions. For example, first, pilot injection for producing a spark in the cylinder with a small amount of injection is performed, and then main injection corresponding to the fuel amount necessary for the original work is performed. At the time of the main injection, the fuel burns following the fire created by the pilot injection. Such combustion suppresses rapid combustion in one cycle, thereby realizing explosion sound and reduction of nitrogen oxides (NOx) during combustion. However, it is necessary to operate the fuel injection valve at a high speed in order to achieve the injection in one cycle in such a very short time, and further, the injection under 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 charging energy of a capacitor provided in a charging circuit to a solenoid coil of the electromagnetic valve at a timing when the electromagnetic valve is operated. This is because the rise of the magnetic flux (= force) in the solenoid coil of the solenoid valve is slow only by application of the battery voltage of the vehicle and cannot be performed in time for control. However, a high voltage equal to or higher than the battery voltage is stored in the capacitor, and the capacitor is connected to the solenoid coil. The magnetic flux rapidly rises by performing discharge from the solenoid valve to perform a high-speed valve opening operation of the solenoid valve. In general, a charge circuit and a constant current circuit are used in combination, and at the beginning of energization, a high current is supplied by the charge circuit to open the solenoid valve, and subsequently the solenoid valve is opened at a predetermined constant current by the constant current circuit. The valve is kept open.

More specifically, in the fuel injection device, the interval between the pilot injection and the main injection may be shortened to 1 msec or less. After the energy used by the capacitor used for driving the pilot injection is released, the charging of the capacitor used for driving the main injection is performed. It is difficult in time to complete.
That is, when the pilot injection and the main injection are performed, the solenoid valve (fuel injection valve) is driven to open and close at such short time intervals that the charging completion time of the capacitor is not reached.
Therefore, a pilot injection capacitor and a main injection capacitor are prepared and individually provided with charge circuits, and the recharge is completed by the fuel injection in the next cycle using the energy of the two charge circuits during one cycle. I was trying to do it.

[0006]

However, when performing multi-stage injection with a short time interval as in the above-described pilot injection and main injection, a charge circuit is required for the number of injections. Further, when performing post-injection after main injection in addition to pilot and main injection, a charge circuit (capacitor) for the post-injection may be required in addition. In this case, the use of the charge capacitor a plurality of times in succession increases the amount of heat generated, and the provision of a plurality of charge circuits makes it necessary to secure a space for circuit installation or increase costs. Occurs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a solenoid valve capable of appropriately performing continuous operation of a solenoid valve using a single charging circuit. A drive device is provided.

[0008]

The solenoid valve driving device according to the present invention includes a constant current circuit for generating a predetermined constant current from a power supply voltage, and a charge circuit having a charge capacitor for storing a voltage higher than the power supply voltage. . According to this solenoid valve driving device, at the beginning of energization of the solenoid coil, the charging energy of the capacitor in the charging circuit is discharged to the solenoid coil of the solenoid valve, whereby the solenoid valve is driven at high speed.
Subsequently, the constant current of the constant current circuit flows through the solenoid coil, so that the operation state of the solenoid valve is maintained.

According to the first aspect of the present invention, when the solenoid valve is continuously driven at a short time interval shorter than the charging completion time of the charge capacitor, the solenoid circuit is energized by the charging circuit each time the solenoid valve is driven. Permission and energization prohibition are repeatedly performed. In this case, since the energization of the solenoid coil by the charging circuit is not performed every time continuously, the electromagnetic valve can be continuously driven even with a single charging circuit. In other words, the inconvenience of the conventional device is avoided, such as increasing the amount of heat generated by continuously using the charge capacitor a plurality of times, increasing the circuit installation space and increasing the cost by providing a plurality of charge circuits. As a result, the continuous operation of the solenoid valve can be properly performed using a single charging circuit.

The invention of claim 1 can be embodied as in claim 2 or claim 3. In the invention according to claim 2,
Only when the power supply voltage is higher than a predetermined threshold voltage (common use range), the solenoid valve is continuously driven at short time intervals, and the energization of the solenoid coil by the charge circuit is prohibited. If the solenoid valve is driven only by the constant current circuit when the power supply voltage drops, the responsiveness of the solenoid valve may be degraded, so the solenoid valve is continuously driven at short time intervals shorter than the charging completion time of the charge capacitor The prohibition of energization of the solenoid coil by the charging circuit is prohibited (permission of energization by the charging circuit is permitted). In this case, the driving method of the solenoid valve can be switched according to the voltage level of the power supply voltage.

According to the third aspect of the present invention, it is determined whether the drive interval of the solenoid valve is longer than the charge completion time of the charge capacitor, and if the drive interval of the solenoid valve is longer than the charge completion time of the capacitor, Permits energization of the solenoid coil by the charge circuit. In other words, when the drive interval of the solenoid valve is longer than the charging completion time of the charge capacitor, continuous drive of the solenoid valve can be performed by continuously using a single charging circuit.

On the other hand, the solenoid valve driving device of the present invention can be applied to a fuel injection device for injecting high-pressure fuel into an internal combustion engine in accordance with energization of the solenoid valve. Thus, the apparatus is embodied as an apparatus that opens and closes a solenoid valve to perform main injection and pilot injection preceding it.

Therefore, in the present invention, during the pilot injection, energization of the solenoid coil by the charge circuit is prohibited, and during the main injection, energization of the solenoid coil by the charge circuit is permitted. In this case, when the pilot and the main injection are performed, the solenoid coil is not continuously energized by the charge circuit, so that the solenoid valve can be continuously driven even with a single charge circuit. More specifically, during the first stage pilot injection, the solenoid coil is energized only by the constant current circuit,
At the time of the main injection of the stage, the solenoid coil is energized by the charge circuit or by the combined use of the charge circuit and the constant current circuit. In other words, the inconvenience of the conventional device is avoided, such as increasing the amount of heat generated by continuously using the charge capacitor a plurality of times, increasing the circuit installation space and increasing the cost by providing a plurality of charge circuits. As a result, the continuous operation of the solenoid valve can be properly performed using a single charging circuit.

The invention according to claim 4 can be embodied as claims 5 to 7. In the invention according to claim 5,
Only when the power supply voltage is higher than the predetermined threshold voltage,
The pilot injection is performed. This means that the pilot injection is not performed when the power supply voltage is reduced, that is, the solenoid valve is not continuously driven in a short time interval shorter than the charging completion time of the charge capacitor. In this case, the driving method of the solenoid valve can be switched according to the voltage level of the power supply voltage.

According to the present invention, it is determined whether or not the injection interval accompanying the opening of the solenoid valve is longer than the charging completion time of the capacitor, and the injection interval by the solenoid valve is determined based on the charging completion time of the capacitor. If it is longer, the energization of the solenoid coil by the charge circuit is permitted in the post injection following the main injection. That is, when the drive interval of the solenoid valve is longer than the charging completion time of the charge capacitor, a single charge circuit is continuously used, thereby enabling continuous drive of the solenoid valve during main injection and post injection.

According to the present invention, the solenoid coil is operated by discharging the charge capacitor during a predetermined number of injections regardless of the number of fuel injections. This also means that the energization of the solenoid coil by the charge circuit is prohibited depending on the number of post-injections. Thus, the amount of heat generated by the charge capacitor can be limited.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. In the present embodiment, the present invention is embodied in a common rail type fuel injection device of a multi-cylinder diesel engine. High-pressure fuel stored in a common rail is supplied from an injector (injector) to an engine combustion chamber in accordance with energization or interruption of energization of an electromagnetic valve. It is injected and supplied. The solenoid valve is driven by a solenoid valve drive circuit including a constant current circuit and a charge circuit, 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 common rail type fuel injection device shown in FIG.
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 well-known microcomputer (hereinafter referred to as a microcomputer) 4 comprising a logic operation circuit. And an electromagnetic valve driving circuit 5 that drives the fuel injection valve 3 to open and close according to a command from the microcomputer 4. The fuel injection valve 3 is provided for each cylinder in a multi-cylinder diesel engine.

Electronic control unit (hereinafter referred to as ECU)
Reference numeral 32 denotes the microcomputer 4 and the solenoid valve drive circuit 5. The microcomputer 4 receives an accelerator opening signal, an engine speed signal, a water temperature signal, a battery voltage signal, and the like from various sensors (not shown).

Here, the microcomputer 4 calculates an optimal fuel injection amount and fuel injection timing based on engine operation information such as the engine speed and the engine load state (accelerator opening), and calculates the electromagnetic valve driving result. The signal is transmitted to the solenoid valve drive circuit 5 as a signal. The solenoid valve driving circuit 5 receives the solenoid valve driving signal and supplies a voltage required for driving to the fuel injection valve 3.
The solenoid valve 17 (in this embodiment, a three-way solenoid valve) of the fuel injection valve 3 is opened. Further, the microcomputer 4 sends to the solenoid valve drive circuit 5 a charge pulse signal for boosting the battery voltage to a voltage higher than the voltage value and a discharge prohibition signal for appropriately prohibiting discharge of charging energy by a charge circuit described later. Send to. The solenoid valve drive circuit 5
The voltage value of the capacitor in the (charge circuit to be described later) is sequentially monitored by the microcomputer 4.

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 monitors the fuel pressure in the common rail 2 with a pressure sensor 14 provided in the common rail 2, and controls the opening and closing of an electromagnetic valve 15 provided in the high-pressure pump 1 to store 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 comprises a fuel injection valve body 16 and a solenoid valve 17, and high-pressure fuel from the common rail 2 is supplied to the fuel injection valve body 16 and the solenoid valve 17. In the fuel injection valve body 16, the fuel chamber 18
A needle valve 19 is arranged inside. Needle valve 1
9 is connected to a piston 20 and is urged by a spring 21 in a direction to close the injection port.

The solenoid valve 17 has a housing 22, and an outer valve 23 is supported in an inner hole 22a so as to be slidable in the vertical direction in the figure. 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 port 26 is connected to a drain tank 27,
Each is connected. 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 solenoid coil 30 is provided above the housing 22. Here, the outer valve 23 is urged downward by a spring 31, and when the solenoid coil 30 is not energized, the first port 24 of the housing 22 communicates with the port 28 of the outer valve 23 and the second port of the housing 22. 25 and outer valve 23
Communicates with the port 29. In such a case, high pressure fuel from the common rail 2 is supplied to these ports 24, 28, 29, 2
5 and the inner hole 23 a of the outer valve 23, the pressure is applied to the upper surface of the piston 20.
9 is pressed downward, and the injection port is held in a closed state (the state shown).

When the solenoid coil 30 is energized, the outer valve 23 is suctioned 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.

On the other hand, when the solenoid coil 30 is not energized, the common rail 2 faces downward with respect to the outer valve 23.
And the urging force of the spring 31 are acting,
In order for the ports 25 and 26 to communicate with each other and 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 at a high speed. Otherwise, the ports 25 and 26 communicate 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 solenoid valve 17 against the fuel pressure reaching a maximum of 150 MPa,
The solenoid valve driving circuit 5 generates a high voltage exceeding the voltage of a battery (12 volts in the present embodiment), which is a DC power source for a vehicle, so that the solenoid coil 30 of the solenoid valve 17
Is discharged when the power is supplied to the solenoid valve 17 to supply a high voltage to the 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 is an electric circuit diagram for explaining a specific configuration of the solenoid valve driving circuit 5. The solenoid valve drive circuit 5 is provided with a charge circuit 33, and the charge circuit 33
, A primary coil 34a of a transformer 34 and a transistor 35 as a boosting switching element are connected in series to a battery + B. The charge pulse signal from the microcomputer 4 is transmitted to the transistor 35. The secondary coil 34b of the transformer 34 has a diode 3
6 and the capacitor 37 are connected in series.

At a connection point A between the diode 36 and the capacitor 37, a diode 39, a solenoid coil 30 of the solenoid valve 17 and a switching element for driving the solenoid valve are connected via a transistor 38 as a switching element for switching the charge circuit. And the transistor 40 is connected in series. In this case, turning on the transistor 38 closes the electric path between the capacitor 37 and the solenoid coil 30, and turning off the transistor 38 opens the electric path between the capacitor 37 and the solenoid coil 30. It has become. The solenoid valve driving transistor 40 is provided with a fuel injection valve 3 provided in each cylinder.
(Electromagnetic valve 17) is provided for each.
The base terminal of each transistor 40 is connected to the microcomputer 4 and the solenoid coil 30 is turned on by the solenoid valve drive signal from the microcomputer 4 to turn on the solenoid coil 30.
Is energized.

A constant current circuit 41 is connected to the battery + B, and a constant current generated by the constant current circuit 41 is supplied to the solenoid coil 30 via a diode 42.

In the solenoid valve driving circuit 5 having the above configuration, when the transistor 40 for driving the solenoid valve is turned on while the transistor 38 for connecting and disconnecting the charge circuit is turned on,
First, a high current due to the charging voltage of the capacitor 37 flows through the solenoid coil 30. Subsequently, the constant current circuit 4
1, a constant current flows. Thus, a steep valve opening operation of the electromagnetic valve 37 can be realized, and the valve opening state can be maintained within a desired injection time.

Next, the operation of the fuel injection device configured as described above will be described. FIG. 3 shows the solenoid valve 17 (fuel injection valve 3).
This routine is executed by the microcomputer 4 for each fuel injection of each cylinder (for example, for every six cylinders, every 120 ° CA).

Now, when the routine of FIG. 3 starts,
The microcomputer 4 firstly starts the charging circuit 33 in step 101.
And a battery voltage (power supply voltage) Vb for supplying a current to the constant current circuit 41, and in a subsequent step 102, the read battery voltage Vb is set to a predetermined threshold voltage V
It is determined whether it is larger than s. When Vb> Vs,
The microcomputer 4 makes an affirmative decision in step 102 and proceeds to step 1
Proceeding to 03, it is determined whether or not the current fuel injection is performed once, that is, whether or not the pilot injection is not performed and the single-stage injection is performed.

Here, whether or not pilot injection is performed is determined based on engine operation information such as engine speed and engine load (accelerator opening). For example, the necessity of pilot injection is determined based on the characteristics shown in FIG. In other words, multi-stage injection including pilot injection is performed in the low-medium-speed / low-medium load region of the engine, and only main injection (one-stage injection) is performed without pilot injection in the high-speed region or high load region of the engine. It is supposed to be.

If the determination in step 103 is affirmative, the microcomputer 4 proceeds to step 104, where 1 is determined by the fuel injection valve 3.
Carry out step injection. That is, the charge circuit 33 and the constant current circuit 41 are used together, and the solenoid coil 30 is used only once.
To drive the solenoid valve 17. However, in the case of this one-stage injection, the constant current circuit 41 is used without using the charge circuit 33.
Only the solenoid valve 17 may be driven. Constant current circuit 41
When only the solenoid valve 17 is driven, a steep high current cannot be obtained.
N is recommended.

If a negative determination is made in step 103, the microcomputer 4 executes multi-stage injection in the processing of step 105 and subsequent steps. Specifically, the microcomputer 4 determines in step 105
The first stage pilot injection is performed by energizing the solenoid coil 30 only with the constant current circuit 41, and the second stage main injection is performed by energizing the solenoid coil 30 by using the charge circuit 33 and the constant current circuit 41 together. Is performed. At the time of pilot injection using only the constant current circuit 41, the transistor 38 for switching the charge circuit is turned off. In addition, at the time of main injection in combination with the charge circuit 33, the transistor 38 is turned on.

Thereafter, the microcomputer 4 determines in steps 106 to 106
At 108, post-injection (injection of the third and subsequent stages) following the main injection is performed. 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 rotation speed and the load. Since this fuel amount is very small, it is not necessary to carry out post-injection every time (if post-injection is not carried out, steps 106 to 108 are not carried out and step 105 is carried out.
After this processing, the routine is terminated as it is).

When the post-injection of the third and subsequent stages is performed, the microcomputer 4 determines in step 106 that the solenoid valve 17
It is determined whether or not the time interval of the fuel injection by the continuous driving (hereinafter, simply referred to as the injection interval) is longer than the charging completion time of the capacitor 37 in the charging circuit 33 (hereinafter, the charging UP time). Here, the injection interval between the main injection and the first post injection or between post injections performed a plurality of times is obtained by converting a minute crank angle set in advance into time. In the rotation range, it is assumed that the charge UP time is shorter than the charge UP time.

If the injection interval is longer than the charge UP time, the microcomputer 4 proceeds to step 107, in which the solenoid coil 30 is energized by the combined use of the charge circuit 33 and the constant current circuit 41 for the required number of post-injections, and the solenoid valve is turned on. 17
Is driven (or once). If the injection interval is shorter than the charge UP time, the microcomputer 4 proceeds to step 10.
Then, the solenoid coil 30 is energized to drive the solenoid valve 17 by the constant current circuit 41 only for the required number of times of post-injection (only one time may be used).

On the other hand, when the battery voltage Vb decreases and it is determined in step 102 that Vb ≦ Vs, the microcomputer 4 proceeds to step 109. Then, the microcomputer 4 determines in a step 109 whether or not the injection interval is longer than the charge UP time.

In step 109, the injection interval is set to charge UP
If it is determined that the time is longer than the time (step 109 is Y
In the case of ES), the microcomputer 4 drives the solenoid valve 17 by energizing the solenoid coil 30 a required number of times by using the charge circuit 33 and the constant current circuit 41 together in step 110.
For example, when the engine is started at a low temperature, a positive determination is made in step 109 and a multi-stage injection is performed in step 110. In the multi-stage injection at the time of starting the engine, a so-called "split injection" is performed before the main injection. In the split injection, even in the same pre-injection, the injection interval between the main injection and the pilot injection is relatively longer, and the multi-stage injection is performed. A charge UP time can be secured between injections.

If it is determined in step 109 that the injection interval is shorter than the charge-up time (NO in step 109), the microcomputer 4 proceeds to step 111 and performs single-stage injection. That is, the charge circuit 33
The solenoid valve 30 is driven by energizing the solenoid coil 30 only once by using the combination of the solenoid valve 30 and the constant current circuit 41.

FIG. 5 is a time chart for more specifically explaining the control operation of the solenoid valve 17 (fuel injection valve 3). The figure shows an example in which multi-stage injection is performed, and periods T1, T2, and T3 in the figure are pilot injection and period T1, respectively.
The period during which the solenoid valve drive signal is turned on to execute the main injection and the post injection is shown. That is, FIG.
Corresponds to a time chart showing in detail the operations of steps 105 to 108 in the flowchart of FIG.

In FIG. 5, first, in a period T1, the first stage pilot injection is performed. At this time, the transistor 38 for disconnecting the charge circuit is turned off by the discharge prohibition signal (OFF signal), so that the solenoid valve 17 is driven only by the constant current circuit 41. Then, when the coil current reaches the valve opening operating current, the fuel injection valve 3 is opened, and fuel injection is started. At this time, the charge valve 33 sends the solenoid valve 1
7 is not supplied with a high current, and the capacitor voltage is maintained in a fully charged state.

Thereafter, in period T2, main injection is performed. In such a case, the charge circuit interrupting transistor 38 is turned on by the discharge inhibition signal (ON signal), so that the solenoid valve 17 is driven using both the charge circuit 33 and the constant current circuit 41. At this time, the charging voltage of the capacitor 37 is discharged at once, and the coil current rises sharply. Then, with the end of the main injection (period T2), charging of the capacitor 37 is started.

Thereafter, post injection is performed in a period T3. At this time, if, for example, the time interval (Ta in the figure) between the pilot injection and the post injection as shown is shorter than the charge UP time, the discharge prohibition signal is turned off. Therefore, in this period T3, the solenoid valve 17 is driven only by the constant current circuit 41.

According to the embodiment described above, the following effects can be obtained. (A) In the present embodiment, at the time of pilot injection when performing multi-stage injection, the energization of the solenoid coil 30 by the charge circuit 33 is prohibited, the solenoid valve 17 is driven only by the constant current circuit 41, and at the time of main injection. In the above, the energization of the solenoid coil 30 by the charge circuit 33 is permitted, and the solenoid valve 17 is driven by using the charge circuit 33 and the constant current circuit 41 together. In this case, since the solenoid circuit 30 is not continuously energized by the charge circuit 33 during the pilot and main injection, the electromagnetic valve 17 can be continuously driven by the single charge circuit 33.
In other words, the inconvenience of the conventional device is avoided, such as increasing the amount of heat generated by continuously using the charge capacitor a plurality of times, increasing the circuit installation space and increasing the cost by providing a plurality of charge circuits. As a result, the continuous operation of the solenoid valve 17 can be properly performed using the single charging circuit 33.

(B) The pilot injection is performed only when the battery voltage Vb is higher than a predetermined threshold voltage Vs. This means that the pilot injection is not performed when the battery voltage Vb decreases, that is, the solenoid valve 17 is not continuously driven at a short time interval shorter than the charging completion time of the capacitor 37.
In this case, the driving method of the solenoid valve 17 can be switched according to the voltage level of the battery voltage Vb.

(C) It is determined whether the injection interval due to the opening of the solenoid valve 17 is longer than the charge UP time (charge completion time) of the capacitor 37. If the injection interval is longer than the charge UP time, the main injection is performed. Then, the energization of the solenoid coil 30 by the charge circuit 33 is permitted in the post injection. That is, by permitting or prohibiting the use of the single charging circuit 33 in accordance with the comparison between the injection interval and the charge UP time, it is possible to realize a suitable continuous drive of the solenoid valve 17 during the main injection and the post injection.

The embodiment of the present invention can be realized in the following modes other than the above. In the fuel injection device according to the above-described embodiment, as described in the flowchart of FIG. 3, the pilot injection, the main injection, the post injection, and the split injection are selectively used as necessary.
The present invention may be embodied in a configuration in which only the pilot injection and the main injection with relatively short injection intervals are performed (the configuration relating to the post injection and the split injection can be omitted).

Regardless of the number of times of fuel injection, the solenoid coil 30 is operated by discharging the charge circuit 33 (capacitor 37) during a predetermined number of injections of the number of injections.
This is because the charge circuit 3 depends on the number of post injections.
3 means that the energization of the solenoid coil 30 is prohibited. Thus, the amount of heat generated by the charge capacitor 37 can be limited.

On the premise that the battery voltage Vb (power supply voltage) can always be maintained at a predetermined threshold voltage Vs or higher, the switching of the solenoid valve driving method according to the battery voltage Vb may not be performed. In such a case as well, when performing the multi-stage injection, the energization of the solenoid coil by the charge circuit is prohibited during the pilot injection, and the energization of the solenoid coil by the charge circuit is permitted during the main injection, so that a single charge circuit is used. The main object of the present invention is to achieve the proper operation of the solenoid valve continuously.

In the flowchart of FIG. 3, in steps 104, 105, 107, 110, and 111, the fuel injection is performed by energizing the solenoid coil 30 by using the charge circuit 33 and the constant current circuit 41 together. In each step, the fuel injection may be performed by energizing the solenoid coil 30 only by the charge circuit 33. For example, when the amount of fuel injection at one time is small, a desired fuel injection amount can be obtained even by driving the solenoid valve only with the charge circuit 33. In this embodiment, a switching element for interrupting the constant current circuit is provided between the constant current circuit 41 and the solenoid coil 30 shown in FIG. 2, and the switching element may be turned off when the constant current circuit 41 is not used. .

In the above embodiment, the present invention is embodied in the three-way solenoid valve 17 for switching three passages (ports). However, the present invention is changed to the two-way solenoid valve 17 for switching two passages (ports). The invention can also be applied to valves.

Further, the present invention can be embodied not only in a fuel injection device for a diesel engine but also in another electromagnetic valve driving device that performs opening and closing operations continuously in a short time. In this case, when the solenoid valve is continuously driven at a short time interval shorter than the charging completion time of the charge capacitor, the energization of the solenoid coil by the charging circuit and the energization prohibition by the charging circuit are performed each time the solenoid valve is driven. The energization permission and energization prohibition of the solenoid coil are desirably performed in the order of "energization prohibition → energization permission". However, the present invention is not limited to this, and either may be performed first.

When the embodiment other than the fuel injection device is used, only when the power supply voltage is higher than a predetermined threshold voltage, the solenoid valve is continuously driven at short time intervals, and the energization of the solenoid coil by the charging circuit is prohibited. It is determined whether the drive interval of the solenoid valve is longer than the charge completion time of the capacitor.If the drive interval of the solenoid valve is longer than the charge completion time of the capacitor, energize the solenoid coil by the charge circuit. You may make it permit every time.

[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 configuration of a solenoid valve driving circuit.

FIG. 3 is a flowchart showing a drive control routine of a solenoid valve.

FIG. 4 is a characteristic diagram showing an execution region of pilot injection (multi-stage injection).

FIG. 5 is a time chart for explaining an operation in the embodiment.

[Explanation of symbols]

Reference numeral 3 represents a fuel injection valve, 4 represents a microcomputer (microcomputer), 5 represents a solenoid valve drive circuit, 17 represents a solenoid valve, 30 represents a solenoid coil, 33 represents a charge circuit, 37 represents a capacitor (charge capacitor), and 41 represents a constant current circuit.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification code FI F16K 31/06 310 F16K 31/06 310A // H01F 7/18 H01F 7/18 D (72) Inventor Toshio Kondo Kariya, Aichi 1-1-1 Showacho Inside DENSO Corporation

Claims (7)

[Claims] 1. A constant current circuit for generating a predetermined constant current from a power supply voltage, and a charge circuit having a charge capacitor for storing a voltage higher than the power supply voltage, wherein a solenoid coil is connected to the constant current circuit and the charge circuit. In an electromagnetic valve driving device that continuously opens and closes a solenoid valve driven by energization at a short time interval less than the charging completion time of the capacitor. A solenoid valve driving device, wherein energization permission and energization prohibition of a solenoid coil by the charge circuit are repeatedly performed. 2. The solenoid valve driving device according to claim 1, wherein only when the power supply voltage is higher than a predetermined threshold voltage,
An electromagnetic valve driving device that continuously drives the electromagnetic valve at short time intervals and prohibits energization of a solenoid coil by the charging circuit. 3. A means for determining whether a drive interval of the solenoid valve is longer than a charge completion time of the capacitor. If the drive interval of the solenoid valve is longer than a charge completion time of the capacitor, the charging is performed. The solenoid valve driving device according to claim 1 or 2, wherein energization of the solenoid coil by the circuit is permitted. 4. A constant current circuit for generating a predetermined constant current from a power supply voltage, a charge circuit having a charge capacitor for storing a voltage higher than the power supply voltage, and energization of a solenoid coil connected to the constant current circuit and the charge circuit. An electromagnetic valve that is driven by the electromagnetic valve, is applied to a fuel injection device that injects high-pressure fuel into the internal combustion engine with the energization of the electromagnetic valve, and is performed at a short time interval less than the charging completion time of the capacitor. An electromagnetic valve driving device that opens and closes a solenoid valve to perform a main injection and a pilot injection preceding the solenoid valve. In a pilot injection, energization of a solenoid coil by the charge circuit is prohibited. An electromagnetic valve driving device characterized in that energization of the solenoid valve is permitted. 5. The solenoid valve driving device according to claim 4, wherein only when the power supply voltage is higher than a predetermined threshold voltage,
An electromagnetic valve driving device for performing the pilot injection. 6. A means for determining whether an injection interval accompanying opening of the solenoid valve is longer than a charge completion time of the capacitor, wherein the injection interval by the solenoid valve is longer than the charge completion time of the capacitor. 6. The solenoid valve driving device according to claim 4, wherein the energization of the solenoid coil by the charge circuit is permitted in a post injection following the main injection. 7. The solenoid valve driving device according to claim 4, wherein the solenoid coil is operated by discharging the charge capacitor during a predetermined number of injections regardless of the number of fuel injections. apparatus.