JPH10339201A - Fuel injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection device with a simple constitution, which has a small response delay from an injection pulse input and a good controllability by which the response delay time is constant. SOLUTION: This fuel injection device is so constituted that a signal from a mechanism detecting a stroke of a corresponding cylinder or a mechanism detecting a fuel pressure is inputted in a driving circuit 31 in which an electric current is carried into an electric coil of an injection valve, and a current is carried in advance as a bias current in such a degree that an injection valve is not opened by itself in the driving circuit 31, avoiding a region in which a pressure in the cylinder increases suddenly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device for an internal combustion engine, and more particularly to an electromagnetic solenoid type fuel injection device for supplying fuel into a cylinder of an automobile engine.

[0002]

2. Description of the Related Art In recent years, in a fuel supply device for an automobile engine, a high precision of a fuel injection amount has been demanded due to a necessity of performing a fine fuel control according to a driving state of the automobile. Particularly, in a direct injection type engine that injects fuel into a cylinder of the engine, the required accuracy is further higher, the dynamic range of the injection amount is high, and the operation delay time of the electromagnet needs to be minimized. Further, since the change in the fuel pressure has a large effect on the injection amount, it is necessary to control the injection amount according to the fuel pressure and other conditions.

As a conventional fuel injection device having such a purpose, for example, a fuel injection device disclosed in Japanese Patent Application Laid-Open No. 4-284159 is known.

In this conventional fuel injection device, one fixed end of a spring is used in an electromagnetic valve that performs a valve opening operation by moving a plunger integrated with a needle valve against the closing force of a spring by the attraction force of an electromagnet. When the fuel pressure is relatively high, the movable force can be moved by other electromagnets, and when the fuel pressure is relatively high, the valve closing force of the spring is reduced. Adjustments were made so as not to differ from each other, so that the operation delay of the electromagnet was reduced, and the fluctuation of the delay time was reduced.

[0005]

However, in the above-mentioned conventional fuel injection device, the electric coil of the electromagnet and the drive circuit for supplying a current to the electric coil are two-dimensional.
Since the system is necessary, the configuration of the fuel injection valve itself becomes very complicated, the mountability is deteriorated due to the increase in cost and size, and the valve opening operation is adjusted by an electromagnet. However, due to its structure, the spring force can be adjusted only in two stages, so it is not possible to cope with a change in fuel pressure at the time of starting or the like. Had the problem of becoming

The present invention has been made in view of the above situation, and an object of the present invention is to provide a drive circuit for an electromagnet of a fuel injection valve with an electric signal indicating a rotation angle of a corresponding cylinder of an engine and a fuel pressure. Information that affects the operation speed of the fuel injection valve, such as an electric signal, is input.In this state, a current that does not open the fuel injection valve is applied to the electromagnet as a bias current before the pulse signal indicating the start of injection is input. Accordingly, it is an object of the present invention to provide a fuel injection device capable of reducing the operation delay of the electromagnet with a simple configuration and reducing the fluctuation of the delay time.

[0007]

In order to achieve the above object, according to the present invention, there is provided a plunger, which is a mover made of a magnetic material, and the plunger which is provided with a small gap from the plunger and is actuated by electromagnetic force. A solenoid comprising an electric coil displaced in the gap, a magnetic yoke and a core, a spring for urging the plunger in a direction to separate the plunger from the core, a needle valve fixed to the plunger, and the needle valve The present invention relates to an electromagnetic solenoid type fuel injection device having a nozzle portion that opens and closes in accordance with the movement of a motor, and a drive circuit that is electrically connected to the electric coil and flows a current to the electric coil at the timing of an input pulse signal. In the drive circuit, the rotational position of the engine crankshaft is input by an electric signal, and the electric signal is No electric current is applied to the electric coil of the electromagnetic solenoid during the firing stroke and the predetermined rotational position before and after the firing stroke, and the electric signal indicates the intake stroke and the compression stroke of the engine and the predetermined rotational position before and after the engine. During the period, drive control is performed such that a current that does not operate the electromagnetic solenoid flows through the electric coil as a bias current.

According to the present invention, the driving circuit is configured such that the fuel pressure in the fuel injection valve or the fuel pipe connected to the fuel injection valve is input by an electric signal, and the magnitude of the fuel pressure indicated by the electric signal is Accordingly, it is desirable to control the drive so as to change the magnitude of the bias current flowing through the electric coil of the electromagnetic solenoid.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments of the invention shown in the accompanying drawings.

FIG. 1 is a diagram showing a first embodiment of the present invention. In the drawing, reference numeral 1 denotes a cylinder block of an engine, reference numeral 2 denotes a cylinder head, reference numeral 3 denotes a piston, and a space 4 surrounded by these denotes a combustion chamber. The combustion chamber 4 is formed with an injection hole 18 of an injection valve.

Reference numeral 11 denotes a yoke made of a soft magnetic material, which forms a magnetic circuit together with the core 12. A spring seat 13 is fixedly installed together with the core 12 on an inner diameter portion of the core 12, and receives one end of the spring 14.

The spring 14 has one end in contact with the plunger 16 in a compressed state.
6, a set load is applied in a direction to separate the core 6 from the core 12. A ball valve element 17 is fixed to the tip of the small diameter portion 16a of the plunger 16, and the ball valve element 17 constitutes an on-off valve together with the injection hole 18.

On the other hand, reference numeral 21 in the figure denotes a high-pressure fuel pump.
The pressure is increased from a to ten and several MPa, and supplied to the injection valve via the fuel pipe 22.

Reference numeral 31 in the drawing denotes a drive circuit for the injection valve, which is connected to the electric coil 15 of the injection valve by a harness 32 and is driven by an injection pulse signal from a control circuit (not shown). The electric coil 15 is configured to be energized. And reference numeral 33
Denotes a crank angle sensor of the engine, which outputs the rotational position of the crankshaft to the drive circuit 31.

Next, the operation of the fuel injection device configured as described above will be described.

First, when no injection pulse is input to the drive circuit 31 and no current flows through the electric coil 15, the ball valve 17 and the plunger 16 fixed to the ball valve 17 are actuated. As shown in FIG. 2, mainly the force Fs due to the spring set load is
(Valve closing direction), and a force Ff (valve closing direction) due to fuel pressure and a force Fc due to in-cylinder pressure of the engine (both open and close directions are considered because the pressure changes from negative pressure to positive pressure).

The valve closing force Ff based on the fuel pressure Pf
Represents the seat area formed by the ball valve element 17 and the injection hole 18 as S
Assuming a, Ff = Pf × Sa, and when there is a change in fuel pressure, the valve closing force Ff also changes proportionally.

Further, the opening / closing valve force Fc due to the in-cylinder pressure Pc also changes according to the stroke of the engine. Fc = Pc × Sa

Here, when the opening / closing valve force Fc is positive, the valve opening force is set, and when the opening / closing valve force Fc is negative, the valve closing force is set.

FIG. 3 shows changes in the in-cylinder pressure Pc. As is apparent from FIG. 3, the cylinder pressure Pc hardly changes during the intake, compression, and exhaust strokes of the engine, but acts on the ball valve element 17 because the cylinder pressure Pc becomes extremely high during the combustion stroke. The valve opening force Fc also becomes extremely large. From these facts, the valve closing force when the fuel pressure is the lowest is Ffin
h, assuming that the valve opening force when the in-cylinder pressure is the highest is Fcmax, in order to prevent the injection valve from opening when current is not flowing through the electric coil 15 in any stroke of the engine, , (Fs + Ffmin)> Fcmax It is necessary to determine the spring set load Fs so that the following relationship is satisfied.

However, the injection pulse is input to the drive circuit 31, that is, the fuel is actually injected from the injection valve only when the corresponding cylinder of the engine is in the intake or compression stroke.

Therefore, when the drive circuit 31 starts energizing the electric coil 15 in this state, the operations of the plunger 16 and the ball valve element 17 of the injection valve become as shown in FIG. 4C. FIG. 6A shows the ejection pulse signal at that time, and FIG. 6B shows the current waveform of the electric coil 15. When the ejection pulse signal is input to the drive circuit 31, the drive circuit 31 starts energizing the electric coil 15.

The current of the electric coil 15 rises with a delay as shown in FIG. Then, as the current increases, an attractive force is generated between the plunger 16 and the end face of the core 12 by the action of the magnetic circuit composed of the yoke 11, the core 12 and the plunger 16. FIG. 5 shows the relationship between the current i and the suction force Fa (i) of the solenoid.

However, while the spring set load Fs is determined by the relation given by Ff = Pf × Sa, the actual valve opening force Fc due to the in-cylinder pressure is determined by the fact that the corresponding cylinder is in the intake or compression stroke. Therefore, the valve opening force Fcmax when the in-cylinder pressure is the highest is extremely small (Fc <Fcmax). Further, the valve closing force Ff due to the fuel pressure is obtained.
Is also larger than Ffmin (Ff> Ffmin).

Therefore, the injection valve opens, that is, the equation [F
s + Ff-Fc = Fa (i)] for a considerable time until the plunger 16 reaches the current value I1 at which the plunger 16 starts moving against the spring set load Fs and the valve closing force Ff due to the fuel pressure. Requires t1.

Therefore, in this embodiment, the signal of the crank angle sensor 33 is input to the drive circuit 31 to avoid the region where the in-cylinder pressure increases before and after the combustion stroke of the corresponding cylinder, and before the injection pulse signal is input. , A bias current I2 is supplied to the electric coil 15 in advance.

The value of the bias current I2 is smaller than the current I1, and the bias current I2 is
Flows only in a region other than the combustion stroke in which the in-cylinder pressure increases, the plunger 16 does not start moving due to this current.

When the ejection pulse signal is input to the drive circuit 31 from this state, the current starts to increase from the bias current I2, so that the current which starts the movement at a time t2 which is much shorter than the considerable time t1. The value I1 will be reached.

As a result, the time until the plunger 16 of the injection valve starts to move can be shortened, so that the injection valve can be driven with a shorter pulse as shown in FIG. 6, and the dynamic range of the injection amount can be expanded. Can be.

FIG. 7 is a view showing a second embodiment of the present invention. In FIG.
The fuel pressure sensor 23 is provided, for example, in the middle of a fuel pipe 22 for supplying fuel to the injection valve from the fuel injection valve. The fuel pressure sensor 23 receives, for example, a fuel pressure on a diaphragm provided therein, and reduces the amount of distortion of the diaphragm. The fuel pipe 22 is configured to convert the electric resistance into a change in electric resistance with a gauge.
Detects the fuel pressure in the drive circuit 31 as an electric signal.
Since the other configurations and operations are the same as those of the first embodiment except for the above, the detailed description thereof is omitted here.

In the present embodiment, the factors that determine the current value I1 at which the plunger 16 starts to move are the valve closing force Ff due to the fuel pressure, the valve closing force Fs due to the spring set load, and the switching valve force Fc due to the in-cylinder pressure. And the magnetic field created by the current i of the electric coil 15 against them, the plunger 16
Is the valve opening force Fa (i) of the electromagnet that attracts the pressure to the core 12. Of these, the opening / closing valve force Fc due to the in-cylinder pressure in the intake stroke and the compression stroke that actually requires fuel injection is extremely small, so ignoring its influence, the valve-opening current I1 is expressed as: Fa (I1) = Ff + Fs Can be expressed in a relationship.

This means that when the fuel pressure changes, the valve opening current I1 of the injector also changes.

Here, according to the present embodiment, the drive circuit 31 receives the signal from the fuel pressure sensor
8, the bias current I2 is changed so as to increase as the fuel pressure increases. By this operation, the time t2 from the input of the injection pulse signal to the opening of the injection valve can be kept constant regardless of the fuel pressure.

In practice, as shown in FIG. 9, when the bias current I2 is changed, the plunger 16 of the injection valve is changed.
Since the time transition of the current (attraction force) after the start of movement of the plunger 16 also changes, it is not strictly possible to make the behavior during the operation of the plunger 16 constant, but compared with the steady value I3 of the normal current. Since the absolute value and the variation width of the bias current I2 are sufficiently small, the influence of this on the injection amount can be ignored.

As described above, even in a fuel system in which the fuel pressure changes, the time delay from the rise of the injection pulse signal to the start of opening of the injection valve is small as shown in FIG. , Can be constant.

[0036]

As described above, according to the fuel injection device of the present invention, the drive circuit for flowing the electric current to the electric coil of the injection valve is provided with a mechanism for detecting the stroke of the corresponding cylinder and a mechanism for detecting the fuel pressure. A signal is input, and the drive circuit avoids an area where the in-cylinder pressure increases rapidly,
Since a current that does not cause the injection valve to open by itself alone is configured to flow in advance as a bias current, the controllability in which the response delay from the injection pulse input is small and the response delay time is constant is low. An excellent effect that a good fuel injection device can be realized with a simple configuration can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a schematic configuration of a fuel injection device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a force acting on a plunger of the fuel injection device.

FIG. 3 is a graph showing a change in in-cylinder pressure in the fuel injection device.

4A and 4B are explanatory diagrams showing the operation of a plunger and a ball valve body of an injection valve in the fuel injection device, wherein FIG. 4A shows an injection pulse signal at that time, FIG. 4B shows a current waveform of an electric coil, and FIG. c) shows the needle valve displacement, (d) shows the current waveform, and (e)
It is explanatory drawing which shows each needle valve displacement.

FIG. 5 is a graph showing a relationship between a current and a suction force of a solenoid in the fuel injection device.

FIG. 6 is a graph showing a relationship between a fuel injection amount and a pulse width of the fuel injection device.

FIG. 7 is a cross-sectional view illustrating a schematic configuration of a fuel injection device according to a second embodiment of the present invention.

FIG. 8 is a graph showing a relationship between a bias current and a fuel pressure of the fuel injection device.

FIG. 9 is a graph showing a temporal transition of a current (attraction force) after the plunger starts moving in the fuel injection device.

FIG. 10 is a graph showing a time delay relationship from a rise of an injection pulse signal to a start of opening of an injection valve in the fuel injection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder block 2 Cylinder head 3 Piston 4 Combustion chamber 11 Yoke 12 Core 14 Spring 15 Current coil 16 Plunger 17 Ball valve element 18 Injection hole 21 High-pressure fuel pump 22 Fuel pipe 31 Injection valve drive circuit 33 Crank angle sensor

Claims (2)

[Claims] 1. A plunger which is a mover made of a magnetic material, an electric coil which is installed with a small gap from the plunger and displaces the plunger in the gap by an electromagnetic force, a solenoid comprising a magnetic yoke and a core. A spring for urging the plunger away from the core, a needle valve fixed to the plunger, a nozzle portion that opens and closes in accordance with the movement of the needle valve, and an electric coil. And a drive circuit for flowing a current to the electric coil at the timing of the input pulse signal, wherein the drive circuit is configured such that the rotational position of the engine crankshaft is inputted by an electric signal, While the electric signal indicates the combustion stroke of the engine and a predetermined rotational position before and after the engine, the electromagnetic solenoid While the electric signal indicates the intake stroke and the compression stroke of the engine and the predetermined rotational position before and after the electric stroke, the electric coil is biased to such an extent that the electromagnetic solenoid does not operate. A fuel injection device that is driven and controlled to flow as an electric current. 2. The driving circuit according to claim 1, wherein the fuel pressure in the fuel injection valve or the fuel pipe connected to the fuel injection valve is input by an electric signal, and the magnitude of the fuel pressure indicated by the electric signal causes the electromagnetic solenoid to operate. 2. The fuel injection device according to claim 1, wherein drive control is performed to change the magnitude of a bias current flowing through the electric coil.