JP2002021679A - Fuel injection device and internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection device, excellent in responsiveness and suitable for injection of fuel, at a low cost and to suppress the occurrence of worsening of control precision of an injection amount occasioned by a change of working environment. SOLUTION: Two power sources are connected to the fuel injection device through a switching means 5 such that the fuel injection device is provided with the two power sources 27 and 28 different in a voltage and the two power sources can be selectively used. A high current energizing time during opening of a valve is decided based on a current detected by a primary delay current detecting means 40 and injection amount control precision on a change of working environment also is ensured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic fuel injection device and, more particularly, to a technique for driving a valve body.

[0002]

2. Description of the Related Art In an electromagnetic fuel injection device for an internal combustion engine, the amount of fuel injection is generally determined by controlling the opening and closing of an electromagnetic valve by an electronic circuit. Specifically, the amount of time to apply a voltage to the solenoid coil of the electromagnetic fuel injection valve is controlled to determine the fuel injection amount.

[0003] As a conventional example of such an electromagnetic fuel injection device, Japanese Patent Application Laid-Open No. H11-141381 discloses a first example in which a first predetermined voltage is applied to a drive circuit of an electromagnetic valve at the start of energization of the electromagnetic valve. By providing the high voltage applying means and the second high voltage applying means for applying the second predetermined voltage, the battery voltage is applied to the solenoid coil for an arbitrary period from when the valve is closed to when it is completely opened. A device has been disclosed in which the time during which a voltage exceeding the voltage can be applied can be set arbitrarily to ensure that the solenoid valve can be opened reliably. Note that this device includes a constant current circuit that supplies a constant current for maintaining or assisting the open state of the solenoid valve, and a switching circuit that controls voltage application to the solenoid valve,
In the valve-open holding operation, voltage and current are applied to the solenoid coil from a vehicle-mounted battery power supply connected via a diode and a resistor.

Japanese Patent Application Laid-Open No. 4-353240 discloses that
Regarding the transition from the energized state in the opening operation of the injection valve to the energized state when holding the injection valve in the open state, the starting current level required to fully open the injection valve is reached,
An apparatus is disclosed that switches to a holding current level after a certain operation time has elapsed, thereby ensuring both responsiveness and stability of the opening operation of the injection valve.

[0005]

In order to improve the fuel efficiency of an internal combustion engine, it is necessary for a fuel injection device to have a wide dynamic range, which is a ratio between the maximum injection amount that can be injected and the minimum controllable injection amount. Therefore, it is required that the valve element accurately responds to the width of the energization time and that the injection amount can be controlled with high accuracy. For this reason, when the valve is opened, a large magnetomotive force is generated and the valve is quickly opened to open the valve. It is necessary to hold the valve body with a small magnetomotive force during holding, and to quickly close the valve when power supply is stopped.

In the device described in Japanese Patent Application Laid-Open No. H11-141381, it is necessary to provide first and second boosting power supply units as first and second high voltage applying means. The boost power supply must be installed separately from the ECU (engine control unit) due to the problem of physical size or heat generation, and the boost power supply itself is expensive. Rises.

Further, the internal combustion engine usually has a plurality of cylinders,
In particular, in an in-cylinder direct injection internal combustion engine, each cylinder needs to be provided with at least one fuel injection device. Therefore, when the number of cylinders increases, the boosting power supply unit becomes large or complicated.

Further, in this apparatus, consideration is given to generating the minimum voltage necessary for maintaining the large current started by the first boosting power supply unit by the second boosting power supply unit. Injection is still limited by the capacity of the capacitors used in the first and second boost power supply units. That is, when the capacitor is discharged, fuel injection cannot be performed, and the condition becomes severe especially when continuous fuel injection is repeatedly performed in a short time. For example, in a direct injection type internal combustion engine, in order to obtain stable combustion, it is effective to perform two injections that are close in time for one combustion, but in this case, the capacity of the capacitor is reduced. It becomes a problem.

Further, in this apparatus, there is no disclosure of a method of appropriately determining a timing for shifting a large current at the time of valve opening from energization to a holding operation.

In the valve opening operation of the fuel injection device, it is desirable that the dynamic range can be maintained even when the applied voltage, the internal resistance of the coil, and the environmental conditions to be used such as the temperature are changed. In addition, it is necessary that the injection amount control accuracy with a small injection amount is not reduced by excessive current input, and it is preferable to compensate for the current supply time or the current value of the large current in the valve opening operation.

Japanese Patent Application Laid-Open No. 4-353240 discloses a method of switching to a holding current level after a current value necessary for fully opening an injection valve has been reached at the time of opening and a certain operating time has elapsed. The appropriate valve opening current value and energization time for balancing valve opening stability and fuel injection amount control accuracy are not necessarily uniquely determined.The applied voltage, coil internal resistance and temperature, etc. Consideration was not always given to changes in usage conditions.

An object of the present invention is to provide a small-sized fuel injection device with high responsiveness at low cost.

It is a further object of the present invention to provide a fuel injection device capable of performing fuel injection with high control accuracy even when the operating conditions change.

[0014]

SUMMARY OF THE INVENTION In order to provide a responsive and compact fuel injection device at low cost, the present invention provides a power supply having two different voltages provided in a vehicle. The two power supplies are connected by switching means so that the higher voltage of the storage battery (battery) can be applied when the valve is opened and the lower voltage can be applied during the holding. As a result, quick opening required at the time of opening the valve and holding of the valve body with a small magnetomotive force are realized, and a voltage raising means for boosting the battery voltage becomes unnecessary, so that an increase in cost can be suppressed.

Further, in order to provide a fuel injection device capable of performing fuel injection with high control accuracy even when the use condition changes, the magnetic attraction force is detected by a primary delay of current or a time integral value. As a result, a desired magnetic attraction force can be generated even when the voltage of the power supply, the internal resistance value of the coil, and the like fluctuate, the valve opening operation can be reliably performed, and a large current flows when the valve is opened. The fluctuation of the magnetic attraction force at the time of switching from the operation (energized state) to the holding operation for maintaining the valve open state can be suppressed, and the accuracy of the injection amount control can be secured.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

First, the configuration of the fuel injection device according to the present invention will be described with reference to FIG. In FIG. 1, the fuel injection device 1 includes a fuel injection valve 2, a drive circuit 3, a low-voltage power supply 27 and a high-voltage power supply 28. The fuel injection valve 2 is a type of a normally closed solenoid valve, and includes a solenoid coil 21.
When the power is not supplied to the valve seat 12, the movable valve body 12 is in close contact with the valve seat 18 by the force urged by the coil spring 17. The fuel injection valve 2 has a core 1
3, a magnetic circuit is constituted by the anchor 11, and the yoke 15, and a gap is provided between the anchor 11 and the core 13.

Next, the basic operation of the fuel injection valve 2 will be described.

When the solenoid coil 21 is energized, a magnetic attractive force is generated between the anchor 11 and the core 13. When the magnetic attractive force is larger than the force of the coil spring 17 pushing the anchor 11 in the valve closing direction, the anchor 11 is moved to the core. 13 and is opened by creating a gap between the valve body 12 and the valve seat 18 joined to the anchor 11 to open the fuel passage 10.
The supplied fuel is injected from the injection port 14.
Here, due to the influence of the eddy current in the magnetic circuit, a magnetic flux is generated with a first-order delay of the current, and the anchor 11 and the core 13
The magnetic attraction force generated during the period becomes a first-order lag of the current. Therefore, the valve body 12 opens with a time lag from the start of energization to the solenoid coil 21.

When the valve is closed, the movable body 12 in the magnetic circuit is in close contact with the valve seat 18, so that the gap between the anchor 11 and the core 13 is large and the magnetic resistance is large. It is in. Further, in the fuel injection valve 2, a force in a valve seat direction (downward in the drawing), that is, a direction in which the valve is kept closed, is applied to the valve body 12 by a coil spring 17 due to a difference between the supplied fuel pressure and a pressure outside the injection port 14. Act on the valve body 12 in addition to the force urged by the valve. Therefore, in order to perform the valve-opening operation of operating from the valve-closed state to the valve-opened state, the magnetic flux is increased against the magnetic resistance due to the gap between the core 13 and the anchor 11, and the valve closing direction acting on the valve body 12 is increased. In order to generate an attraction force that opens the valve against the force, it is necessary to excite the solenoid circuit 21 with a large current to excite the magnetic circuit. The operation of supplying a large current when the valve is opened as described above is hereinafter referred to as a valve opening overexcitation operation.

When the valve is opened by the valve opening over-excitation operation, the gap between the anchor 11 and the core 13 is narrowed and the magnetic resistance is reduced, and the pressure difference due to the fuel pressure before and after the valve body 12 is balanced by the flow of fuel. The fluid force acting on the valve body 12 is only due to the pressure loss, and the force acting on the valve body 12 in the valve closing direction is reduced. Therefore, the current for maintaining the valve opening state may be smaller than the current value required for the valve opening operation. The operation of maintaining the valve open state in this manner is referred to as a holding operation.

When the energization of the solenoid coil 21 is stopped, the magnetic flux in the magnetic circuit decreases, the magnetic attraction force decreases, and the valve body 12 is seated on the valve seat 18 by the force urged by the coil spring 17. Fuel injection is stopped. Also at this time, due to the influence of the eddy current, the magnetic attraction force falls with a first-order delay from the stop of the current, and the valve body 12 closes with a time lag from the stop of the energization.

The amount of fuel injection is controlled by the length of time during which the solenoid coil 21 is energized.

Next, the configuration of the drive circuit 3 for driving the fuel injection valve 2, the valve opening overexcitation operation when the valve is opened, and the holding operation when the valve is held will be described.

One terminal 16a of the solenoid coil 21 is grounded via a switch 32 and a current detecting resistor 24. The non-grounded terminal 16b of the solenoid coil 21 is connected to a low voltage side (for example, 14V) power supply 27 via the switch 22 and the diode 30 constituting the switching means 5, while the high voltage side (for example, 42V). ) The power supply 28 is also connected via the switch 23 constituting the switching means 5. The non-grounded terminal of the solenoid coil 21 is grounded via a diode 31 whose forward direction is from the ground to the solenoid coil 21.

Each of the low-voltage power supply 27 and the high-voltage power supply 28 is a storage battery (battery) mounted on the vehicle.

The switches 22 and 23 are turned ON / OFF.
The signal to be turned off is input from the current control circuit 29.
A semiconductor switch element (such as a field-effect transistor or a bipolar transistor; a P-channel power MOSFET in this example) may be used for the switches 22 and 23.

The current control circuit 29 performs an ON / OFF operation of the switches 22 and 23 based on a pulse signal (Ti pulse) having a time width input from the ECU 4.

The ECU 4 operates the internal combustion engine (rotation speed,
Load, accelerator opening, etc.)
A Ti pulse having a time width corresponding to the determined injection amount is output to the current control circuit 29. The ECU 4 determines the time width of the Ti pulse based on the determined injection amount, the fuel pressure (fuel supply pressure), and the power supply voltages of the power supplies 27 and 28. The ECU 4 outputs the determined Ti pulse to the current control circuit 29.

The side of the current detection resistor 24 that is not grounded is connected to the current control circuit 29 and the ECU 4.

FIG. 2 shows the Ti pulse output from the ECU 4, the ON / OFF operation of the switches 22 and 23, the voltage applied to the solenoid coil 21, the current flowing through the solenoid coil 21 (the voltage between the terminals of the current detection resistor 24). ) And the lift amount of the valve element 12.

First, a series of operations relating to driving of the fuel injection device will be described.

When the Ti pulse is input to the current control circuit 29, the current control circuit 29 first turns on the switches 32 and 23, and supplies the high voltage power supply 2 to the solenoid coil 21.
8 is applied. By supplying a current from the power supply 28 on the high voltage side, a large magnetomotive force can be quickly applied to the magnetic circuit, and a magnetic flux is generated against the magnetic resistance due to the gap between the core 13 and the anchor 11, The valve is opened by applying magnetic attraction to the valve element 12.
Here, even when the switch 23 is ON, the presence of the diode 31 allows a current to flow from the high-voltage power supply 28 to the low-voltage power supply 27 through the diode that the switch 22 has equivalently. Can be prevented.

After the valve is opened, the current control circuit 29 turns off the switch 23 and shifts to the holding operation. When the valve 12 is held, the switch 23 is turned off, and the current control circuit 29 is turned off.
Turns on / off the switch 22 so that the current value detected by the current detection resistor 24, specifically, the voltage between terminals of the current detection resistor 24, takes a predetermined value range, and controls so that a constant current flows. . That is, the switch 22 is turned off when the voltage between the terminals of the current detection resistor 24 exceeds a predetermined value, and the switch 22 is turned on when the voltage between the terminals of the current detection resistor 24 becomes smaller than the predetermined value. The predetermined value of the voltage between the terminals of the current detection resistor 24 when the switch 22 is turned on may be different from the predetermined value when the switch 22 is turned off. It is preferable that the predetermined value of the voltage is larger than that when the voltage is turned off. As described above, the O of the switch 22 is controlled so that the voltage between the terminals of the current detection resistor 24 falls within a predetermined range.
By controlling N / OFF, the ON / O of the switch 22 is controlled.
It is possible to prevent the interval between the FFs from being too small, and not to exceed the limit of the frequency at which the switching element can switch.

When the Ti pulse falls, the switch 22
Is stopped and turned off, and the switch 32 is turned off. The switch 32 turns off the switch 23
This is for preventing the current from flowing back to the coil after the Ti pulse is stopped and preventing the current from falling sharply from the diode 31 that prevents the current from flowing back to the solenoid coil 21 to generate an excessive flyback voltage. is there.

By connecting the two power supplies 27 and 28 to the solenoid coil 21 via the switching means 5 as described above, the solenoid coil 21 can be selectively energized as necessary from both high voltage and low voltage power supplies. Will be able to do that. At the time of opening the valve, the voltage is applied from the high voltage power supply side to increase the time change rate of the current, and it becomes possible to quickly and supply a large current, so that the time change rate of the magnetic attraction force at the time of opening the valve also increases, Therefore, the valve element 1 responds to the input Ti pulse.
2 can respond quickly.

The two power supplies 2 mounted on the vehicle as described above
By using the switching means 7 and 28 by the switching means 5, it is not necessary to use a voltage increasing means for the valve opening over-excitation operation, so that space can be saved and the cost of the fuel injection device can be suppressed.

As described above, since the current is directly supplied from the power supply to the solenoid coil 21 without using the voltage raising means, it is necessary to apply a high voltage without depending on the discharge from the high voltage storage means such as a capacitor. Thus, the high voltage application time can be set arbitrarily regardless of the capacity of the high voltage storage means and the stored charge. This makes it possible to reliably open the valve even when the fuel pressure, temperature, coil internal resistance, wiring resistance, power supply voltage, etc., change and a high voltage needs to be applied for a relatively long time. Become.

In addition, the fact that a high voltage can be applied from the power supply without depending on the discharge from the high voltage storage means means that the voltage is increased and the high voltage is stored between one fuel injection and the next injection. This time is not required, so that it is possible to perform the fuel injection several times closely at short intervals.

Further, by using a diode 30 having a forward direction from the switch 22 to the solenoid coil 21 between the switch 22 and the contact between the switch 22 and the switch 23 as a component of the switching means 5, the voltage of the voltage is reduced. It is possible to prevent a current from flowing from the high voltage power supply 28 to the low voltage power supply 27 when two different power supplies are connected.

The operation during the valve-opening overexcitation can be performed by turning on the switch 23 as described above. However, when the valve-opening overexcitation operation is performed for a relatively long time for the purpose of opening the valve more reliably, , The switch 23 may be ON / OFF controlled, for example, so that the detection value from the current detection resistor 24 becomes constant. By extending the time of the valve opening over-excitation operation in this way, it is possible to reduce the instability of the mechanical motion state such as the vibration of the valve body 12 immediately after the valve is opened,
This can prevent the accuracy of the fuel injection amount control from deteriorating,
By controlling the current, it is possible to prevent an unnecessary current from being supplied at the time of opening the valve, to prevent an increase in valve closing delay in a small Ti pulse width due to excessive generation of a magnetic attraction force due to an excessive current. Control accuracy of the fuel injection amount in the pulse width can be ensured.

In the holding operation, by controlling the current flowing through the solenoid coil 21 to be constant as described above, the magnetic attraction force in the holding state can be kept constant regardless of the power supply voltage. , The valve closing delay is constant, and the accuracy of the injection amount control of the fuel injection device can be improved.

According to the constant current control as described above, the holding current can be set smaller than the current for valve opening overexcitation, and the inductance of the solenoid coil 21 for high speed valve opening overexcitation. Even if the resistance is reduced or the resistance is reduced, the current value is independent of this.
The current does not flow more than the current value required for maintaining the open state of No. 2. This has the effect of making the magnetic attraction force at the time of holding smaller than that at the time of valve opening. Therefore, the valve closing delay when injection is stopped, that is, when current supply is stopped, can be reduced.

The current control circuit 29 is connected to the low-voltage power supply 27.
The voltage applied to the solenoid coil 21 is turned ON / OFF by using the voltage supplied from the power supply, so that the time change rate of the current when the voltage is turned ON is reduced as compared with the case where a high voltage is applied, and the switch 22 is turned on. The frequency at which the switch 22 is turned on / off is reduced, so that heat generation due to switching loss of the switch element used for the switch 22 can be suppressed, and a low-priced switch element can be used to reduce cost. Alternatively, when the width of the threshold value of the current control is determined so that the switching frequency becomes equal to that when the high voltage is applied and held, the width of the threshold value is small because the rate of change of the current with time is small. As a result, the accuracy of current control can be improved. Further, since the rate of change of current with time is small, radiation noise is reduced, and a shielded wire or the like for suppressing radiation noise can be replaced with an inexpensive one.

The resistance value and the number of turns of the solenoid coil 21 can be applied with a current value that saturates with the applied voltage at the time of holding and a magnetomotive force that can be held. Further, when the valve is opened, a sufficiently high speed and sufficient magnetomotive force can be obtained. The current control operation can be omitted by selecting it so that it can be turned on. By not controlling the current value by turning on / off the switch, a sudden change in the current value does not occur, and radiation noise caused by a sudden change in the current value does not occur. As a result, such as shielded wires to prevent radiation noise from leaking to the outside,
There is no need to take noise countermeasures, and costs can be reduced.

In the following, a description will be given of a method of determining the transition timing with respect to the transition from the valve opening over-excitation operation to the holding operation.

FIG. 3 shows the transition from the input of the Ti pulse to the over-opening operation and holding operation of the solenoid coil 2.
1, a current value flowing through the solenoid coil 21 (a detection voltage from the current detection resistor 24), a detection value of a first-order lag current simulating a magnetic attraction force, a magnetic attraction force,
And the lift amount of the valve element 12.

In the over-opening operation of the valve, when a current is applied to the solenoid coil 21, the magnetic attraction rises with a first-order delay of the current. When the magnetic attraction force exceeds the magnitude of the force required to open the valve (valve opening level in the figure) determined by the sum of the force of the coil spring 17 pressing the valve body 12 and the force due to the supplied fuel pressure, the valve opens. Lifting of the body 12 is started. When the valve body 12 is lifted, the valve body 12 collides with a stopper provided in the fuel injection device and eventually opens while being bounced. When the valve body 12 is opened, the anchor 11 and the core 1
Reducing the gap between the three reduces the reluctance, increases the magnetic flux and increases the magnetic attraction. On the other hand, the level of the magnetic attraction force required for holding (holding limit level in the figure) decreases because the fluid force decreases by opening the valve. After the valve is opened, the current continues to increase with a first-order lag until the valve-opening overexcitation operation ends, and when the valve-opening overexcitation operation is stopped and the current value is reduced to the holding current, the magnetic attraction force Decreases with a first-order delay of the current value, and converges to a certain level of magnetic attraction (holding level). When the Ti pulse falls and the holding current is turned off, the magnetic attraction falls with a first-order delay, and when the magnetic attraction falls below the holding limit level, the valve body 12 is displaced in the valve seat direction and closes.

Here, the change in the magnetic attraction force due to the reduction of the gap due to the opening of the valve element 12 is a change by a certain amount determined by the characteristics of the magnetic circuit constituting the fuel injection valve 2. In addition, there is no such change between the opening and closing of the valve, and the current becomes first-order lag. The magnetic attraction between the valve opening and the valve closing which determines the characteristics of the fuel injection valve can be represented by a first-order lag value of the current.

FIG. 4 shows a primary operation in the case where the switching from the valve opening over-excitation operation to the holding operation is performed by providing a threshold value for the current value and detecting that the current value has reached a predetermined value. 3 shows an example of a delay current value and a lift amount of the valve element 12.

When the voltage of the power supply fluctuates and the voltage rises, the current rises rapidly, but the first-order lag current, that is, the magnetic attraction force, rises later than the current and opens when the magnetic attraction force is insufficient. The current of the valve over-excitation operation is stopped, and the magnetic attraction force is reduced while the movement of the valve body 12 is not stable. Therefore, the movement of the valve body 12 when the valve is opened becomes unstable, and the control accuracy of the fuel injection amount is reduced. Getting worse. In a low voltage state, the rise of the current value is slow, the time required to reach a predetermined current value is long, and the magnetic attraction force is excessively generated. As a result, the small Ti pulse width The valve closing delay increases, and the control accuracy of the fuel injection amount deteriorates.

Therefore, in order to maintain the control accuracy of the fuel injection amount even when the power supply voltage fluctuates, it is necessary that the magnetic attraction force is generated without excess or deficiency.

In the present invention, in order to solve the above-mentioned problem, from the operation of the valve opening overexcitation, that is, the rapid current supply by turning on the switch 23, the operation of the holding excitation, that is, the switch 23 is turned off and the switch 22 is turned on / off. The timing of switching to the constant current operation by turning OFF is determined based on the voltage between the terminals of the capacitor 26 of the primary delay current detecting means 40 connected to the current control circuit 29 shown in FIG.

The first-order lag current detecting means 40 is a means comprising a capacitor 26 and a resistor 25 for simulating the magnetic attraction. The first-order lag current detecting means 40 includes a capacitor 26 and a resistor 25 connected in series, and is connected in parallel with the current detecting resistor 24.

The primary delay current detecting means 40 forms a CR series circuit by the capacitor 26 and the resistor 25 connected in series. The voltage applied to both ends of the primary delay detecting means 40 is applied to the terminal of the current detecting resistor 24. It is a value proportional to the inter-voltage, that is, the value of the current flowing through the coil. With such a connection, a voltage value proportional to the first-order lag value of the current value can be generated between the terminals of the capacitor 26.

The respective values of the capacitor 26 and the resistor 25 connected in series are determined by the time constant of the CR series circuit formed by them and the time constant of the magnetic circuit of the injector, that is, the magnetic constant with respect to the current applied to the solenoid coil 21. It is preferable to set the time constant so as to match the time constant of the rise of the suction force. Generally, the magnetic attraction force becomes a first-order lag of the current flowing through the solenoid coil 21 due to the magnetic field formed by the eddy current generated in the magnetic circuit when the current is applied, and thus, by using the first-order lag detecting means 40 as described above, The rise of the magnetic attractive force can be read out as the voltage between the terminals of the capacitor 26, and it can be easily detected that the magnetic attractive force required for opening the valve has been reached.

In this embodiment, one terminal of the current detecting resistor 24 and the capacitor 26 is grounded, and the other terminal is used as an input to the current control circuit 29 so that a voltage with the ground becomes an input signal. However, the current detection resistor 24 and the capacitor 26 do not necessarily need to be directly connected to the ground. If the current detection resistor 24 and the capacitor 26 are not directly connected to the ground, the voltage between the terminals of the current detection resistor 24 and the terminal of the capacitor 26 are used. May be input to the current control circuit 29.

Control using the primary delay current detecting means 40 will be described with reference to FIG.

The current control circuit 29 receives the Ti
The switch 23 is turned on in response to the pulse input, the voltage on the high voltage power supply side is applied to the solenoid coil 21, and a current for valve-opening overexcitation flows. During this time, the current control circuit 29
Monitors the voltage between the terminals of the capacitor 26, and turns the switch 23 OFF when the voltage between the terminals reaches a predetermined value.
Set to FF.

The threshold value of the first-order lag current value corresponding to the magnetic attraction required to open the valve is determined by the operating environment conditions of the fuel injection device,
That is, it is preferable that the temperature can be changed depending on the temperature, the supplied fuel pressure, and the like. For example, when the supply fuel pressure is high, by increasing the threshold value, a sufficient magnetic attraction force can be supplied, and the valve can be reliably opened even when the fuel pressure is high. When the supply fuel pressure is low, the threshold value is reduced so that an excessive magnetic attraction force is not supplied immediately after the stop of the valve opening overexcitation, so that the valve closing delay with a small Ti pulse width increases. Can be suppressed, and the injection amount control accuracy can be improved. By properly controlling the threshold value of the first-order lag current value according to the level of the fuel pressure, fuel injection can be reliably performed without impairing the injection amount accuracy over a wide range of fuel pressure.

When the switch 23 is turned off, the application of the high voltage is stopped, and the current flowing through the solenoid coil 21 decreases sharply. At this stage, the operation is switched to the above-mentioned holding excitation operation, and the switch 2 is switched by the current control circuit 29.
The constant current control by ON / OFF operation of No. 2 is performed.

By monitoring the voltage between the terminals of the capacitor 26, the primary delay value of the current can be monitored, and the same effect as monitoring the magnetic attractive force can be obtained. It is possible to generate the magnetic attraction necessary for opening the valve regardless of the influence of the power supply voltage, the resistance of the wiring, the internal resistance of the coil, etc.

FIG. 6 shows a comparison between the characteristics of the fuel injection amount with respect to the Ti pulse width according to the present invention and the method using current control.

The switching from the valve opening over-excitation operation to the holding operation is performed as follows.
In the case of a method for detecting that the current value of the solenoid coil 21 has reached a predetermined value, since the current value does not match the magnetic attraction force as described above, the magnetic attraction force immediately after switching is excessive. Or shortages. If the suction force immediately after the switching is excessive, the valve closing delay increases, so that the fuel injection amount changes in a direction to increase with respect to the input Ti pulse width, and the fuel injection amount T
The linearity with respect to the i-pulse deteriorates, and the accuracy of the fuel injection amount control deteriorates. Also, if the magnetic attraction force immediately after switching is insufficient, the movement of the valve body after opening the valve becomes unstable due to bouncing, and for small pulse widths, the valve closing delay becomes small, and the injection amount changes in a direction to decrease. I do. Therefore, the linearity of the injection amount with respect to the Ti pulse width input to the fuel injection device is deteriorated, and the accuracy of the fuel injection amount control is deteriorated. According to the present invention, the timing of the transition from the valve opening over-excitation operation to the holding operation is determined using the first-order lag current value simulating the magnetic attractive force, so that the magnetic attractive force immediately after the switching is almost constant. Therefore, the problem of excess or deficiency of the magnetic attractive force as described above does not occur, the linearity of the fuel injection amount with respect to the Ti pulse width is improved, and the accuracy of the fuel injection amount control can be improved.

In the valve opening overexcitation operation, the capacitor 2
6 so that the terminal voltage of the switch 6 falls within a predetermined range.
May be turned ON / OFF to extend the time of valve opening overexcitation. By extending the time of the valve opening over-excitation operation in this way, the instability of the mechanical motion state such as the vibration of the valve immediately after the valve is opened can be attracted to the valve opening side for a required time by the magnetic attraction force. By continuing, it is possible to prevent the accuracy of the fuel injection amount control from deteriorating. In addition, the magnetic attraction force within the extension time can be kept constant irrespective of the extension time of the valve-opening overexcitation, and the generation of an excessive magnetic attraction force can be suppressed. As a result, it is possible to prevent an increase in valve closing delay with a small Ti pulse width, and to ensure control accuracy of the fuel injection amount with a small Ti pulse width. In addition, since the control is based on the magnetic attraction force, it is constant when the valve is opened without affecting factors such as the voltage of the high-voltage side power supply, the internal resistance of the solenoid coil 21, the resistance of the wiring, and the temperature that may affect the injection amount accuracy. The magnetic attraction force can be given, and the injection amount accuracy can be improved.

In the current control of the holding excitation operation, control may be performed so that the voltage between the terminals of the capacitor 26 falls within a predetermined range, instead of keeping the current value constant. FIG.
Are the switches 12, 1 when the control is performed such that the voltage between the terminals of the capacitor 26 falls within a predetermined range as described above.
3 shows the operation, the voltage applied to the solenoid coil 21, and the current flowing through the solenoid coil 21. When the control is performed so that the voltage between the terminals of the capacitor 26 is constant, the voltage between the terminals of the capacitor 26 is slower than the change in the current value because the voltage between the terminals of the capacitor 26 has a first-order lag. ON / O current
The frequency of the FF can be reduced, the heat generation of the semiconductor switching element can be suppressed, and the cost can be suppressed by using a low-priced semiconductor switching element.

By determining the current for the holding operation based on the voltage between the terminals of the capacitor 26 as described above, it is possible to apply the voltage until the magnetic attraction after stopping the application of the high voltage is reduced to the attraction required for holding. Will be suspended. As a result, the magnetic attraction force after the stop of the valve-opening overexcitation operation falls to a predetermined value at a large time change rate, and the time until the magnetic attraction force becomes constant can be shortened. The constant magnetic attraction force means that the valve closing delay is constant, and by using such a method, a shorter Ti
The linearity of the injection amount with respect to the Ti pulse width is maintained up to the pulse width, and a small injection amount can be obtained with high accuracy.

The effect of lowering the magnetic attraction force to the holding level immediately after the stop of the valve opening overexcitation operation as described above is effective even when the current value is controlled to be within a predetermined range even when the high voltage application is stopped. It is also possible to obtain ON / OFF of the switches 22 and 23 by the voltage between the terminals of the capacitor 26 as described above during the time from immediately after to the transition to the holding operation. That is, immediately after the high voltage is stopped by turning off the switch 23, both the switches 22 and 23 are turned off until the voltage between the terminals of the capacitor 26 corresponding to the magnetic attraction decreases to a predetermined value instead of a predetermined time or a predetermined current value.
By stopping the voltage application to the solenoid coil 21 at F, the magnetic attraction force immediately after the high voltage application is stopped becomes a predetermined value regardless of the conditions such as the power supply voltage, the internal resistance of the coil, the resistance of the wiring, and the temperature. Can be shifted to the holding operation at the point in time. As a result, a constant magnetic attraction force can be obtained immediately after the application of the high voltage is stopped, the valve closing delay quickly becomes a constant value, and the accuracy of the fuel injection amount can be obtained even with a small Ti pulse width.

The above-mentioned determination of the transition timing from the valve opening over-excitation operation to the holding operation is based on the detection of the primary delay current by the primary delay current detecting means 40. It can also be performed by replacing it with an integrated value detecting means. Generally, the time integral of the current value matches well with the primary delay value of the current value in a range where the time is smaller than the time constant, and therefore, the primary delay detecting means 40 of the current value is replaced with the time integral value detecting means. be able to.

The ECU 4 connected to the current detecting means 24 is an example of the means for detecting the time integral of the current value. When the current value is monitored by the ECU 4,
This can be performed by periodically adding current values monitored inside the ECU 4 without using a means for separately obtaining a first-order lag current value. Since the calculation is light, it is possible to calculate the timing of transition from the valve opening over-excitation operation to the holding operation without requiring a large amount of calculation time, and to perform the switching operation accurately.

When the primary delay detecting means 40 is not used, the switching operation from the valve opening overexcitation to the holding excitation can be performed by detecting that the current value in the valve opening overexcitation operation has exceeded a certain threshold value. it can. The above threshold value may be determined according to the use environment conditions of the fuel injection device, that is, the supply fuel pressure, the temperature, the internal resistance of the coil, the resistance of the wiring, the power supply voltage and the like.

FIG. 8 shows an electromagnetic fuel injection valve 2 provided to inject fuel directly into a cylinder 51, a fuel pressure sensor 50, an accumulator 52, and a high-pressure pump 53.
, An internal combustion engine including a feed pump 54 and a fuel tank 55.

As shown in FIG. 8, by providing a pressure sensor 50 for measuring the fuel pressure in the fuel pipe and connecting the pressure sensor 50 to the ECU 4, the ECU 4 can obtain information on the fuel pressure. The threshold can be determined based on the fuel pressure. Note that the pressure sensor 50 may be connected to the ECU 4 via an A / D converter. Also, by connecting the outputs of the power supplies 27 and 28 to the ECU 4, the ECU 4 can obtain information on the power supply voltage, and can determine the threshold based on the power supply voltage. Note that the output unit of the power supply may be connected to the ECU 4 via an A / D converter.

For example, when the supply fuel pressure is high, the required magnetic attraction force can be obtained by increasing the threshold value, and the valve opening operation can be reliably performed. Also, when the internal resistance of the coil is large and the power supply voltage is low, the time required to reach the required magnetic attractive force is long, and therefore the magnetic attractive force, which is the primary delay of the current value, is short. Since the ratio between the magnetic attraction force and the current value is larger than when the target value is reached in time, lowering the threshold value can prevent excessive magnetic attraction force from being generated. The accuracy of fuel injection amount control with a short Ti pulse width can be ensured while reliably opening the valve.

The switching operation from the over-excitation to the holding excitation can also be performed by limiting the time for performing the opening excitation operation. The time for performing the valve-opening over-excitation operation may be determined according to the usage environment conditions of the fuel injection device, that is, the supply fuel pressure, temperature, internal resistance of the coil, resistance of the wiring, power supply voltage, and the like.

For example, in a state where the load is large, such as a high supply fuel pressure, a low power supply voltage, a high wiring resistance, and a high internal resistance of the coil, the valve opening overexcitation time is extended to open the valve. Can be ensured. In addition, when the load is low, such as when the supply fuel pressure is low, the power supply voltage is high, the wiring resistance is low, and the internal resistance of the coil is low, reducing the valve opening over-excitation time will reduce the excess magnetic attraction force. Injection can be suppressed, and as a result, the accuracy of fuel injection amount control with a short Ti pulse width can be ensured.

In the case where the time for the valve opening overexcitation operation is limited as described above, the switching from the valve opening overexcitation operation to the holding operation may be determined by the ECU 4 instead of the current control circuit 29. That is, the ECU 4 may output a pulse having a time width of the valve opening over-excitation operation to the switch 23.

When the fuel injection device according to the present invention is connected to a power supply of, for example, a high-voltage power supply voltage of 42 V and a low-voltage power supply voltage of 14 V, the number of turns of the fuel injection device coil is 80 to 80 V. When the frequency is relatively small, such as about 120 times, the change in the current waveform of the valve opening overexcitation operation becomes large with respect to the change in the power supply voltage and the resistance value of the coil. By the control, the time of the valve opening over-excitation operation can be appropriately limited, and the control accuracy of the injection amount is not impaired. Further, when the number of turns of the coil is relatively large, such as about 120 to 200 turns, when the resistance value of the coil is relatively large, such as 1.5 to 2.5Ω, the time change rate of the current during the valve opening overexcitation operation Therefore, when the valve opening over-excitation operation time is determined by setting a threshold value for the current value, the valve opening over-excitation operation time changes in response to a change in the power supply voltage and a change in the coil resistance value. Although the accuracy of the amount control is impaired, the over-excitation operation time of the valve opening is controlled based on the primary delay current value or the integral value of the current value according to the present invention, whereby the over-excitation operation time of the valve opening can be appropriately controlled, and the injection amount control There is no loss of accuracy.

When the fuel injection device 1 of the above embodiment is employed in the internal combustion engine shown in FIG. 8, stable combustion can be obtained by performing two injections that are temporally close to each combustion. In this embodiment, since the battery voltage is applied to the fuel injection valve 2 without being boosted, it is not necessary to use a capacitor for boosting. Therefore, there is no need to consider that the capacitor is discharged due to insufficient capacity, and it is possible to stably perform close fuel injection.

[0080]

According to the present invention, a fuel injection device having good responsiveness and suitable for fuel injection is provided by providing two power supplies having different voltages so that a high voltage can be applied when the valve is opened and a low voltage can be applied when the valve is held. Can be provided at low cost.

Further, since the first-order lag value or the time integral value of the current is detected to switch between the over-excitation and the holding excitation, the voltage of the power supply, the internal resistance of the coil, and the like are changed. In addition, a desired magnetic attraction force can be generated, a reliable valve opening operation can be performed, and a change in the magnetic attraction force at the time of switching can be suppressed, thereby ensuring the accuracy of the injection amount control.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a fuel injection device according to an embodiment of the present invention.

FIG. 2 is a time chart showing a driving operation of the fuel injection device according to one embodiment of the present invention.

FIG. 3 is a time chart showing a magnetic attraction force and a valve body operation in driving the fuel injection device according to one embodiment of the present invention.

FIG. 4 is a time chart showing a driving operation of the fuel injection device in which a variation in a power supply voltage is compensated by a coil current value in one embodiment of the present invention.

FIG. 5 is a time chart illustrating a driving operation of the fuel injection device in which power supply voltage fluctuation is compensated by a first-order lag current value in one embodiment of the present invention.

FIG. 6 is a relationship diagram showing a relationship between a fuel injection amount and a Ti pulse width when one embodiment of the present invention is used.

FIG. 7 is a time chart showing a driving operation when a first-order lag current value is used for current control in one embodiment of the present invention.

FIG. 8 is a wiring diagram showing connections when the present invention is mounted on an internal combustion engine.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fuel injection device, 2 ... Fuel injection valve, 3 ... Drive circuit, 4
... ECU, 5 ... Switching means, 10 ... Fuel passage, 11 ... Anchor, 12 ... Valve, 13 ... Core, 14 ... Injection port, 15 ... Yoke, 16a ... Plus terminal, 16b ... Ground terminal, 17 ... Coil spring , 18 ... valve seat, 21 ... solenoid coil, 22 ... electric switch, 23 ... electric switch, 24 ... current detection resistor, 25 ... resistor, 26 ... capacitor, 27 ... low voltage side power supply, 28 ... high voltage side Power supply, 29
... current control circuit, 30 ... diode, 31 ... reflux diode, 32 ... electric switch, 40 ... primary delay current detection means.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Makoto Yamamon 502, Kandate-cho, Tsuchiura-shi, Ibaraki Pref. Machinery Research Laboratories, Hitachi, Ltd. Inside the Machinery Research Laboratory (72) Inventor Tohru Ishikawa 2520 Address Takahiroba, Hitachinaka City, Ibaraki Prefecture Inside the Automotive Equipment Group, Hitachi, Ltd. Within the Automotive Equipment Group (72) Inventor Takashi Hasunuma 2477 Takaba, Hitachinaka-shi, Ibaraki F-term in Hitachi Car Engineering Co., Ltd. 3G066 AB02 AD07 BA19 BA51 BA61 CC05Z CD26 CE29 3G301 JA14 LB01 LC01 NA04 PG01Z PG02Z 3H106 DA07 DA13 DA23 DB02 DB12 DB23 DB32 DC02 DC17 DD03 EE05 EE22 FA01 KK18

Claims (6)

[Claims] 1. A fuel passage, comprising: a valve seat; a valve body for opening and closing a fuel passage between the valve seat; and driving means having at least one coil to drive the valve body. A fuel injection device comprising: an electromagnetic fuel injection valve that opens and closes to inject fuel, and a control device that controls energization of the coil, wherein an electric power between two storage batteries mounted on a vehicle and the coil is provided. An opening / closing device for opening and closing the connection, wherein the control device connects a storage battery having a higher voltage among the two storage batteries to the coil when the valve body is driven in a valve opening direction from a valve closing state; In a state where the valve body completes the valve-opening operation and maintains the valve-open state, the device that controls the opening / closing device so as to connect a low-voltage storage battery of the two storage batteries to the coil. Boosting the voltage of each battery Fuel injection system and applying the Ku said coil. 2. The fuel injection device according to claim 1, further comprising: means for detecting a first-order lag value of a current value flowing through the coil, wherein the control device determines the second-order lag value based on the first-order lag value. The fuel injection device, wherein the switching device is controlled so as to open a connection between a storage battery having a high voltage among the two storage batteries and the coil. 3. The fuel injection device according to claim 2, wherein said means for detecting a first-order lag value includes a capacitor and a resistor. 4. The fuel injection device according to claim 1, further comprising: means for detecting a time integrated value of a current value flowing through the coil, wherein the control device is configured to detect the time integrated value based on the time integrated value. The fuel injection device, wherein the switching device is controlled so as to open a connection between a storage battery having a high voltage among the two storage batteries and the coil. 5. The fuel injection device according to claim 4, further comprising a current value detecting means for detecting a current value flowing through the coil, wherein the means for detecting a time integrated value of the current value comprises an arithmetic means, A fuel injection device, wherein the time integration value is detected by numerically calculating a current value detected by the current value detection means. 6. An electromagnetic fuel injection valve, wherein the amount of fuel injected from the electromagnetic fuel injection valve is controlled by controlling energization from a storage battery to a coil provided in the electromagnetic fuel injection valve. In an internal combustion engine that generates power by driving a piston by burning injected fuel in a cylinder, two storage batteries having different voltages as the storage batteries, and an electrical connection between the two storage batteries and the coil An opening / closing device that opens and closes, as a control device that controls energization of the coil, when the valve body is driven in a valve opening direction from a closed state, a storage battery having a higher voltage among the two storage batteries is connected to the coil. The opening and closing device is connected to connect the low-voltage storage battery of the two storage batteries to the coil in a state where the valve body completes the valve-opening operation and maintains the valve-open state. And a control device for controlling an internal combustion engine and applying a voltage of said two battery to the coil without boosting, respectively.