JPH11107882A - Drive device for fuel injection valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a cost of a drive device for a fuel injection valve. SOLUTION: Before the fuel injection period of an electromagnetically-driven fuel injection valve, preliminary energization is effected on the electromagnetic coil of the fuel injection valve and a current at the vicinity of upper limit current value S/L1 is caused to flow. After entering a fuel injection period, an energization current to an electromagnetic coil is rapidly increased to fully open a valve element, and thereafter, held at the vicinity of a holding current value S/L2 to hold an energization current in an opening valve state. This constitution, since an energization current is increased for opening the valve from a state that an electromagnetic coil is stored at the electromagnetic coil before a fuel injection period, increases a valve opening speed even when a source voltage is low, and ensures responsiveness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive device for an electromagnetic (solenoid) type fuel injection valve.

[0002]

2. Description of the Related Art In recent years, in a spark ignition type engine such as a gasoline engine, fuel is directly injected into a combustion chamber, and in a low / medium load region, the fuel is injected in a compression stroke to thereby form a combustible mixture only near an ignition plug. A technology has been developed in which stratified combustion is performed in a stratified form, thereby enabling combustion with a significantly lean air-fuel ratio to greatly improve fuel efficiency and exhaust gas purification performance.

In this type of fuel injection valve, it is necessary to inject the fuel at a high pressure in a short period against the compression pressure during the compression stroke. In order to expand the dynamic range of the fuel injection amount under such restrictions, it is necessary to improve the responsiveness of the fuel injection valve. For this reason, conventionally, when the fuel injection valve is opened, the high voltage stored in the capacitor is applied to the electromagnetic coil of the fuel injection valve, and the current is rapidly raised to shorten the valve opening time. A relatively small current required to maintain a valve open state by applying a battery voltage to the battery is supplied.

[0004]

However, such a conventional fuel injection valve driving device requires a high voltage charging circuit capable of coping with the entire range of engine rotation for each cylinder. A high-voltage circuit and a switching circuit of a complicated drive system for driving the fuel injector while switching and using a high voltage and a battery voltage are required.In addition, since the current consumption is large, a shield for reducing radiation noise is required. A line was needed. For this reason, the circuit scale becomes large and the cost is high.

The present invention has been made in view of such a conventional problem. By improving the method of energizing an electromagnetic coil of a fuel injection valve, it becomes possible to drive the fuel injection valve only at a low voltage. It is an object of the present invention to provide a fuel injection valve drive device that solves the above problems.

[0006]

According to a first aspect of the present invention, there is provided a fuel injection valve driving apparatus in which a valve element is opened and closed by turning on and off energization of an electromagnetic coil.
A preliminary current is applied to the electromagnetic coil so that the valve body does not open before the fuel injection period, and after the fuel injection period, the current is rapidly increased to fully open the valve body. Until the operation is completed, a holding current sufficient to maintain the valve open state of the valve element is supplied.

According to the first aspect of the present invention, by supplying a preliminary current to the electromagnetic coil of the fuel injection valve before the valve is opened before the fuel injection period, electromagnetic energy is previously supplied to the electromagnetic coil. Since the current is stored, if the valve body rapidly increases the current from this state, the valve body is fully opened quickly in a short time. Therefore, responsiveness can be ensured even at a low voltage.
Further, after the valve element is fully opened, the power consumption can be minimized by reducing the holding current to a value that can maintain the valve open state.

The invention according to claim 2 is characterized in that an upper limit current value at the time of the preliminary energization is set based on a fuel supply pressure to the fuel injection valve. According to the invention according to claim 2, the current supplied to the electromagnetic coil required to open the fuel injection valve changes depending on the fuel supply pressure, and accordingly, by setting the upper limit current value at the time of preliminary energization, Necessary and minimum energization can be performed.

Further, the invention according to claim 3 is characterized in that the energizing time at the time of the preliminary energizing is set based on a power supply voltage. According to the third aspect of the present invention, the time required to rise from the start of energization to the upper limit current value at the time of the preliminary current changes, so that the energizing time at the time of the preliminary energization is set accordingly. In addition, minimum energization can be performed.

The invention according to a fourth aspect is characterized in that an energizing time for rapidly increasing a current to the electromagnetic coil after the fuel injection period is set based on a power supply voltage. According to the invention according to claim 4, since the speed at which the current is rapidly increased after the fuel injection period starts depends on the power supply voltage, it is necessary and necessary to set the energizing time at the time of the current sudden increase in accordance with the power supply voltage. Minimal energization can be performed.

The invention according to claim 5 is characterized in that the fuel injection valve is mounted so as to directly inject fuel into a combustion chamber of an internal combustion engine. According to the fifth aspect of the invention, a sufficient effect can be exerted when applied to a drive device of a fuel injection valve of a gasoline engine or the like that performs stratified combustion by injecting fuel in a compression stroke.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a circuit configuration of a fuel injection valve driving device according to an embodiment of the present invention. Although not shown, the fuel injection valve according to the present embodiment is mounted so as to directly inject fuel into a combustion chamber of a spark ignition engine such as a gasoline engine, and in particular, injects fuel at a high pressure during a compression stroke in a low to medium load region. This applies to those that perform stratified combustion.

In FIG. 2, an electromagnetic coil 1 of a fuel injection valve is shown.
Is connected to a battery power supply VB via a first switching transistor Tr1 in series, and the other end of the electromagnetic coil 1 is grounded via a second switching transistor Tr2 and a current detecting resistor R1 in series. You. The flywheel diode FD is grounded via the electromagnetic coil 1, the second switching transistor Tr2 and the current detecting resistor R1 in parallel.

The terminal voltage of the current detecting resistor R1 is A /
An injection timing arithmetic unit 3 composed of a CPU or the like of a microcomputer based on the value of the current flowing through the electromagnetic coil 1 that is input to a current detection circuit 2 composed of a D converter or the like and detected by the current detection circuit Sets an injection control signal as described later and outputs the signal to the first switching transistor Tr1 and the second switching transistor Tr2. As a result, the switching of the first switching transistor Tr1 and the second switching transistor Tr2 is controlled, the energization of the electromagnetic coil 1 is controlled, and the opening and closing of a valve (not shown) is controlled. In addition, between the electromagnetic coil 1 and the second switching transistor Tr2, the back electromotive force generated when the energization of the electromagnetic coil 1 is turned off is quickly absorbed, and the first switching transistor Tr1 and the second switching transistor Tr2 are absorbed. Is connected.

Next, the operation of this embodiment according to the injection control signal of the injection timing arithmetic unit 2 will be described with reference to the time chart of FIG. The fuel injection period is set based on the operating state of the engine, the preliminary energization to the electromagnetic coil 1 is started before the set time T1 before the fuel injection period, and the energizing current for the set time T2 is rapidly increased after entering the fuel injection period. ,
Thereafter, the holding current is reduced to a holding current that can hold the valve open state until the end of the injection period.

The upper limit current value S / L at the time of the preliminary energization
Numeral 1 is set to a predetermined level at which the valve body does not open, and after the first switching transistor Tr1 and the second switching transistor Tr2 are turned on to start energizing the electromagnetic coil 1, the energizing of the detected electromagnetic coil 1 is performed. When the current reaches the upper limit current value S / L1, the first switching transistor Tr1 is turned off for a predetermined time to decrease the current value, and is turned on again to increase the current to increase the upper limit current value S / L.
When the value reaches 1, the switching control of turning off for a predetermined time is repeated to control the value near the upper limit S / L1.

A set time T2 from the start of the fuel injection period
Keeps the ON state of the first switching transistor Tr1 and the second switching transistor Tr2,
Since the current is increased from the state where the electromagnetic coil 1 is energized near the upper limit current value S / L1 and the electromagnetic energy is stored, the valve body is quickly opened and fully opened. After the lapse of the set time T2, the first switching transistor Tr1
Is turned off, the current supplied to the electromagnetic coil 1 is reduced,
When the detected current value decreases to a holding current value S / L2 (set to a value slightly larger than the upstream current value S / L1) necessary to hold the valve open, the first switching transistor Tr1 Is turned on for a predetermined time, the energizing current is increased, the energizing current is turned off again, the energizing current is reduced, and when the detected current value decreases to the holding current value S / L2, the switching control of turning on for a predetermined time is repeated, and the holding current value is repeated. Control is performed near S / L2.

When the fuel injection period ends, the first switching transistor Tr1 and the second switching transistor Tr2 are both turned off, and the power supply to the electromagnetic coil 1 is stopped immediately. With this configuration, the fuel injector can be driven with high responsiveness only by the battery power supply voltage, whereby the high-voltage power supply circuit can be eliminated, and the driving method can be greatly simplified to reduce the circuit scale.
Furthermore, since the current consumption can be reduced, a shield line for reducing radiation noise is not required, and the cost can be greatly reduced.

FIG. 3 shows a circuit configuration of a fuel injection valve driving device according to a second embodiment of the present invention. The fuel pressure sensor 5 for detecting the fuel supply pressure to the fuel injection valve is provided in the configuration of FIG. In addition, the upper limit current value S / L1 at the time of the preliminary energization is variably set based on the detected fuel supply pressure. That is, the valve opening time of the fuel injection valve increases in proportion to the fuel supply pressure because the valve body is pressed in the valve closing direction by the fuel supply pressure. In order to improve the effect of the fuel supply pressure on the valve opening time, the higher the fuel pressure, the larger the upper limit current value S / L1 is set, and the electromagnetic energy is stored in the electromagnetic coil 1 as long as the valve is not opened. To Thereby, necessary and sufficient preliminary energization can be performed.

Strictly speaking, the in-cylinder pressure in the combustion chamber acts as a valve opening force. (The biasing force in the valve closing direction due to the fuel supply pressure is sufficiently larger than the valve closing force. However, a sensor for detecting the in-cylinder pressure may be provided, and the upper limit current value S / L1 may be corrected and set based on the in-cylinder pressure. FIG. 4 shows a circuit configuration of a driving device for a fuel injection valve according to a third embodiment of the present invention.
And a configuration in which a detection value of the battery voltage is input and the energization time T1 of the preliminary energization is variably set.

That is, the pre-energization may be performed by energizing the electromagnetic coil 1 near the upper limit current value S / L1 immediately before the start of the fuel injection period, and the switching control time for repeating the ON / OFF of the first switching transistor Tr1 May be short, and longer will only increase power consumption. Then, the increasing speed of the energizing current after the start of the pre-energization increases as the battery voltage increases, and the time required to reach the upper limit current value S / L1 also decreases as the battery voltage increases. With a configuration in which the pre-energization time T1 is shortened, necessary and sufficient pre-energization can be performed.

The first switching transistor T
The ON state of r1 is continued and the energizing current is increased to the upper limit current value S / L.
Since the rate of increase of the current at the time of sudden increase from 1 also increases with the increase of the battery voltage, if the ON duration T2 is also shortened with the increase of the battery voltage, the necessary and sufficient ON duration is obtained. can do. further,
When the fuel supply pressure is high, the valve closing speed is large, and the valve opening speed of the valve body tends to be delayed.
2 may be added.

Further, by combining the second embodiment and the third embodiment, the setting of the upper limit current value S / L1 according to the fuel supply pressure and the setting of the pre-energization time T1 according to the battery voltage are performed. It goes without saying that the setting, and further, the setting of the ON continuation energization time T2 according to the battery voltage and the fuel supply pressure may be performed.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of a fuel injection valve driving device according to a first embodiment of the present invention.

FIG. 2 is a time chart showing an operation state of the embodiment.

FIG. 3 is a circuit configuration diagram of a fuel injection valve driving device according to a second embodiment of the present invention. 4 is a flowchart illustrating a routine for learning characteristics of a fuel pressure sensor according to the embodiment.

FIG. 4 is a circuit configuration diagram of a fuel injection valve driving device according to a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electromagnetic coil 2 Current detection circuit 3 Injection timing calculation device 5 Fuel pressure sensor Tr1 First switching transistor Tr2 Second switching transistor VB Battery voltage

Claims (5)

[Claims] 1. A driving device for a fuel injection valve in which a valve body is opened and closed by turning on and off energization of an electromagnetic coil, wherein a current is supplied to the electromagnetic coil such that the valve body does not open before a fuel injection period. And the current is rapidly increased from the start of the fuel injection period to fully open the valve body, and thereafter, the valve body can be kept open until the fuel injection period ends. A driving device for a fuel injection valve, characterized by flowing a holding current. 2. The fuel injection valve driving device according to claim 1, wherein an upper limit current value at the time of the preliminary energization is set based on a fuel supply pressure to the fuel injection valve. 3. The fuel injection valve driving device according to claim 1, wherein the energization time during the pre-energization is set based on a power supply voltage. 4. An energizing time for rapidly increasing a current to said electromagnetic coil after entering said fuel injection period is set based on a power supply voltage. 4. The driving device for a fuel injection valve according to claim 1. 5. The fuel injection valve according to claim 1, wherein the fuel injection valve is mounted so as to directly inject fuel into a combustion chamber of an internal combustion engine. Drive.