JPH05321732A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To reduce noise and NOx as well as to change the initial fuel injection rate and thereby perform an optimum fuel injection control by accomplishing drive control a fuel injection valve by means of controlling a plural number of energizing periods and non-energizing periods for a drive solenoid of the fuel injection value. CONSTITUTION:An drive solenoid M3 of a fuel injection valve M2 of an internal combustion engine M1 is supplied with electric current from an energizing means M4. On the other hand, the circuit of the drive solenoid M3 is turn on and off through a switch means M5. In this case, the operating condition of the internal combustion engine M1 is detected by an operating condition detecting means M6. Based on the detected operating condition, the injection rate of a fuel injection valve 2 is calculated by an injection rate calculation means M7. Corresponding to the calculated injection rate, a plural number of energizing organ and a non-energizing organ for the drive solenoid M3 are provided. The switch means 5 is drive controlled in accordance with the established value and the remanent magnetic field in the drive solenoid M3 caused by energizing is regulated by means of a timing control means M6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device for an internal combustion engine, which supplies fuel by drivingly controlling a solenoid valve injector (fuel injection valve).

[0002]

2. Description of the Related Art Conventionally, as a device for supplying fuel to a diesel engine,
For example, a high-pressure fuel injection device using a common rail type unit injector is known. In this device, fuel is injected and supplied by a solenoid valve injector,
The injection rate of the injector is uniquely determined by the diameter of the injection nozzle and the injection pressure.

However, the diesel engine generally has a problem that combustion noise and NO _x are generated due to the ignition delay of the fuel, and as described above, the injector and the injector which uniquely determine the injection rate generate noise and noise. The NO _x problem was not solved. As a countermeasure against this, for example, a so-called pilot injection technique (see JP-A-63-5140 and JP-A-62-129540) in which a small amount of fuel is injected before a fixed period of time during the normal fuel injection is adopted. In this case, the problem can be solved by driving the injector twice, but another problem as described below occurs.

That is, the injector has a slight operation delay in the initial stage of fuel injection because the rise of the drive current is delayed due to the inductance of the coil. Therefore, in order to eliminate the operation delay of the injector, as shown in FIG.
As shown in (a), in addition to the valve opening current for normal fuel injection (corresponding to the injection pulse), from the high pressure generator (corresponding to the trigger pulse) at the same time when the energization of this valve opening current is started.
A technique for supplying an exciting current to quickly perform an initial operation of an injector at the time of starting fuel injection (Japanese Patent Publication No. 49-4524).
8). However, if it is attempted to improve the initial operation of the injector by this technique when performing the pilot injection, a circuit for supplying each exciting current as shown in FIG. 14 (b) when the injector is driven twice ( A rush current circuit for discharging the energy charged by the capacitor is required, which causes a problem that the circuit configuration becomes large-scale.

[0005] The present invention is made to solve the above problems, a simple configuration, by changing the fuel injection rate at the start of fuel injection, fuel injection of an internal combustion engine that can achieve a reduction in noise and NO _X An object is to provide a control device.

[0006]

As shown in FIG. 1, the present invention for achieving the above object includes an energizing means M4 for supplying a current to a drive solenoid M3 of a fuel injection valve M2 of an internal combustion engine M1. Switch means M5 for turning on and off the circuit of the drive solenoid M3, and the fuel injection valve M2.
In a fuel injection control device for an internal combustion engine that drives the engine to control fuel injection, an operating state detecting means M6 for detecting an operating state of the internal combustion engine M1 and the operating state detecting means M
6, an injection rate calculating means M7 for obtaining an injection rate of the fuel injection valve M2 in accordance with the operating state detected by the driving solenoid M6, and the drive solenoid M3 prior to opening the fuel injection valve M2.
A first energization period for energizing the fuel injection valve, a second energization period for opening the fuel injection valve M2, and an energization suspension period between the first energization period and the second energization period for the injection rate calculation means M7.
Is set according to the injection rate obtained by the above, the switch means M5 is driven according to the set value, and the residual in the drive solenoid M3 due to the energization of the first energization period at the start timing of the second energization period. A fuel injection control device for an internal combustion engine is characterized by including timing control means M8 for adjusting a magnetic field.

[0007]

In the fuel injection control device for the internal combustion engine of the present invention, the current is supplied to the drive solenoid M3 of the fuel injection valve M2 of the internal combustion engine M1 by the energizing means M4. Then, based on the operating state of the internal combustion engine M1 detected by the operating state detecting means M6, such as the rotational speed and the load, the injection rate calculating means M7 determines the injection rate of the fuel injection valve M2. Furthermore,
The timing control unit M8 sets the first energization period, the second energization period, and the energization stop period according to the injection rate, and drives the switch unit M5 that turns on and off the circuit of the drive solenoid M3 according to the set values. Then, the on / off timing of the circuit of the drive solenoid M3 is adjusted.

That is, the timing control means M8 can control the first energization period, the second energization period and the energization suspension period by adjusting the on / off timing of this circuit, so that the second energization period is started. It is possible to adjust the residual magnetic field due to energization during the first energization period during the period. Then, by adjusting the residual magnetic field, the fuel injection rate in the initial stage of the fuel injection can be finely adjusted.

For example, by the timing control means M8,
By setting the first energization period TP and the energization suspension period TI as shown in FIG. 2A, as shown in FIG.
The magnetic flux (of the drive solenoid M3) due to the first energization period TP and the magnetic flux due to the second energization period TM partially overlap (that is, at the start timing of the second energization period TM). As a result, as shown in FIG. 2C, the lift amount of the nozzle of the fuel injection valve M2 (nozzle lift) increases at a predetermined inclination according to the degree of overlap of the magnetic flux (degree of residual magnetic field) (note that , Without the first energization period TP, it becomes extremely gentle as shown by the dotted line in the figure). As a result, the injection rate at the initial stage of fuel injection changes according to this nozzle lift, as shown in FIG.

FIG. 3 shows the relationship between the magnetic flux density and the energization suspension period TI. The larger the first energization period TP and the shorter the energization suspension period TI, the larger the magnetic flux density, and the fuel injection valve M2 is driven. It has a property that the excitation energy is large. Furthermore, FIG. 4 shows the relationship between the valve opening time (time until the valve is fully opened) and the magnetic flux density. The larger the magnetic flux density, the shorter the valve opening time.

Therefore, by utilizing these properties, the timing control means M8 adjusts the first energization period TP, the second energization period TM, and the energization suspension period TI to drive the fuel injection valve M2, whereby the fuel is injected. Suitable control of fuel injection is realized by changing the initial injection rate of injection.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 5 is a schematic configuration diagram showing the overall configuration of the fuel injection control device of the embodiment. As shown in the figure, the fuel injection control device 1 of the present embodiment is a pressure-accumulation type device, and includes a 6-cylinder diesel engine 2 and a fuel injection valve (injector) 3 for injecting and supplying fuel to each cylinder of the diesel engine 2. A pressure accumulating chamber (common rail) 4 for accumulating high-pressure fuel to be supplied to the injector 3, a fuel supply pump 5 for pumping high-pressure fuel to the common rail 4, and an electronic control unit (ECU) 6 for controlling these.

In accordance with the control command from the ECU 6, the fuel supply pump 5 sucks the fuel stored in the fuel tank 10 through the low-pressure pump 11, pressurizes it to a high pressure inside itself, and pressurizes the fuel at a high pressure. The fuel is pressure-fed to the common rail 4 via the supply pipe 12. Each injector 3 is connected by a pipe 13 to a common rail 4 that stores high-pressure fuel. Then, by opening and closing the electromagnetic control valve 14 provided in each injector 3, the high pressure fuel accumulated in the common rail 4 is injected into the combustion chamber of each cylinder of the diesel engine 2.

The ECU 6 includes an engine speed Ne detected by a speed sensor 7 and an accelerator sensor 8 as an operating state detecting means, and an accelerator opening A _CC indicating an engine load.
Is taken in and feedback control of the common rail pressure is performed in order to realize the fuel injection pressure in which the combustion state of the diesel engine 2 is optimized according to the detected operating state.

The engine speed Ne and the accelerator opening A detected by the speed sensor 7 and the accelerator sensor 8 are also used.
Based on the _CC , the control valve 14 of the injector 3 is drive-controlled to control the fuel injection described in detail later. The opening / closing operation of the control valve 14 of the injector 3 is
It is executed based on an injector control command from the ECU 6 to the injector drive circuit 20 shown in FIG. This injector control command is for controlling ON / OFF of the injector solenoid 21 of the control valve 14 to adjust the fuel injection amount and the fuel injection timing, and is a detection signal from the rotation speed sensor 7 or the accelerator sensor 8. Is calculated based on the detected values of the rotation angle sensor 7 and a cylinder discrimination sensor (not shown), etc.
Is output from.

The control command for the fuel supply pump 5 is also output at a predetermined timing based on the detected values from the rotation angle sensor 7, the common rail pressure sensor 9, the cylinder discrimination sensor and the like. Next, the structure of the injector drive circuit 20 will be described with reference to FIG.

As shown in the figure, the injector drive circuit 20
Is connected to a power supply terminal 22 with a coil L for charging and a first transistor T ₁ for switching, and a constant current circuit 23, a first diode 24, and an injector solenoid 2 are connected.
1 and the second transistor T ₂ for switching are connected in sequence. The downstream side of the coil L and the injector solenoid 21 are connected via the second and third diodes 25 and 26, and the capacitor C is connected between the two diodes 25 and 26. Furthermore, both transistors T ₁ ,
The base terminal B _1, B ₂ of T ₂ are connected to the ECU 6, the other end of the transistors T _1, the emitter terminal E ₁ of the T _2, E ₂ and the capacitor C is grounded.

Here, the base terminal B ₁ of the first transistor T ₁ is turned on and off by the ECU 6 (based on the detected voltage of the capacitor C) so that the voltage charged by the capacitor C is constant. A control signal is input. The base terminal B ₂ of the second transistor T ₂ is connected to the ECU
An injector drive control signal is input from 6.

Next, the operation of the injector drive circuit 20 will be described. First, when the first transistor T ₁ is turned on, a current flows from the power supply terminal 22 through the coil L in the direction of arrow a due to the inductance of the coil L. At this time, the second transistor T ₂ is off. In this state, the injection preparation is completed.

Next, when the first transistor T ₁ is turned off, current flows in the direction of arrow b to charge the capacitor C. Next, when the second transistor T ₂ is turned on, a large current flows in an instant from the capacitor C in the direction of the arrow c, giving an exciting current to the injector solenoid 21.
At the same time, a constant current flows from the constant current circuit 23 in the direction of arrow d, giving a valve opening current to the injector solenoid 21. Therefore, the injector 3 is driven by the exciting current and the valve opening current.

In the present embodiment, this second transistor T ₂
By performing the drive control of 2 times, the valve opening current is supplied to the injector solenoid 21 twice. That is, in the first energization, the exciting current and the valve opening current shown by the diagonal lines in FIG. 2A are supplied to the injector solenoid 21,
Since the charge of the capacitor C is consumed by this supply operation, only the valve opening current flows in the second energization.

Next, the control process of the ECU 6 for driving and controlling the injector 3 using the injector drive circuit 20 will be described with reference to the flowchart of FIG. First,
In step 100, the operating states of the engine 2 such as engine speed Ne, accelerator opening A _CC , cooling water temperature, intake air temperature, intake air pressure, etc. are detected based on the output signals from the respective sensors.

In the following step 110, the basic injection amount, injection start timing, and
Calculate the injection pressure. In the following step 120, based on the engine speed Ne and the accelerator opening degree A _CC , the injection rate level determination map as shown in FIG. Determine the base level. The basic level is modified according to the cooling water temperature.

In the following step 130, the common rail pressure is detected. In the following step 140, the step 1
Injection amount obtained at 10, 120, 130, injection start timing,
Based on the common rail pressure and the injection rate level, as shown in FIG. 9, the energization start timing TT from the reference position of the predetermined crank angle, the first energization period TP, the energization suspension period (injection suspension period) TI, the second energization. The period TM is calculated.

Here, the respective times TT, TP, TI, T
The process of calculating M will be described. The energization start timing TT is set by the following formula (1), of which TBASE is a normal injection start signal timing, and TA is a correction set by the level as shown in FIG. 10 (a). It is a value.

TT = TBASE-TA (1) The first energization period TP including energization of the exciting current is shown in FIG.
As shown in (b), it is set by the injection rate level and the common rail pressure. When the common rail pressure is high, a large amount of fuel is injected even with a small amount of electricity, so
The first energization period TP is set to be short.

The injection stop period TI is set by the injection rate level and the common rail pressure, as shown in FIG. 10 (c). In addition, when the common rail pressure is high, as shown in FIG.
Since the first energization period TP is set small as shown in (b), the energization pause period TI is set small in order to obtain the required magnetic flux density as shown in FIG.

Second energization period TM for determining the main injection amount
Is set by the injection amount and the common rail pressure calculated in step 11, as shown in FIG. And
In the following step 150, the injector 3 is driven on the basis of the respective timings TT, TP, TI, TM calculated in step 140, and the present processing is terminated.

That is, in this embodiment, the second transistor T ₂ which is a switch is driven based on the respective timings TT, TP, TI, TM, etc. set according to the respective levels, so that FIG. As shown, a desired excitation state by the drive current can be applied to the injector 3 before opening the valve. Thereby, the initial rise of the nozzle lift (injection rate) is adjusted, and appropriate fuel injection such as pilot injection, boot injection, trapezoidal injection, and rectangular injection is appropriately selected according to the operating state, and easily executed. can do.

Particularly, in the trapezoidal injection in this embodiment, an appropriate magnetic flux can be left in the injector solenoid 21 by adjusting the width of the excitation pulse and the injection rest period, so that the inclination of the initial injection can be arbitrarily set. The significant effect is that it can be changed.

Specifically, for example, as shown in FIG.
First fuel injection during idle, low load operation and high load operation
Appropriate for the cooling water temperature and engine speed Ne during the period
Since a precise injection rate can be set, diesel engine
Noise reduction of engine 2 and NO _XCan be reduced
it can.

It is needless to say that the present invention is not limited to the above embodiment and can be implemented in various modes without departing from the scope of the present embodiment. For example, without using the configuration of the inrush current circuit composed of the coil L, the first transistor T ₁ , and the capacitor C of the above-described embodiment, the drive timing of the first transistor T _{2 is} simply adjusted to adjust the first energization period, The second energization period and the energization rest period may be controlled to adjust the residual magnetic field of the injector solenoid 21 to control the initial injection rate of the injection injection. In this embodiment, there are advantages that the same effects as the above-mentioned embodiments are obtained and that the structure is simplified.

[0033]

As described in detail above, in the fuel injection control device for an internal combustion engine of the present invention, the timing control means allows
By controlling the first energization period, the second energization period, and the energization suspension period to drive the fuel injection valve, the initial injection rate of fuel injection can be changed, so that suitable control of fuel injection in a diesel engine is possible. It can be performed. As a result, there is a remarkable effect that noise and NO _x generated from the diesel engine can be reduced with a simple device configuration.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram illustrating a basic configuration of the present invention.

FIG. 2 is an explanatory diagram showing the principle of the present invention.

FIG. 3 is a graph showing the relationship between the magnetic flux density and the first energization period and energization pause period.

FIG. 4 is a graph showing the relationship between valve opening time and magnetic flux density.

FIG. 5 is a system configuration diagram showing a fuel injection control device of the present embodiment.

FIG. 6 is a circuit diagram showing an injector drive circuit.

FIG. 7 is a flowchart showing a control process of the injector of this embodiment.

FIG. 8 is an explanatory diagram showing a level determination map.

FIG. 9 is a timing chart showing an energization period of the injector.

FIG. 10 is a graph showing the relationship between level and energization period.

FIG. 11 is a graph showing the relationship between the injection amount and the second energization period.

FIG. 12 is an explanatory diagram showing various injection states.

FIG. 13 is an explanatory diagram illustrating an injection state according to an operating state.

FIG. 14 is an explanatory diagram showing a conventional technique.

[Explanation of symbols]

M1 ... Internal combustion engine M2 ... Fuel injection valve M3 ... Drive solenoid M4 ... Energizing means M5 ... Switch means M6 ... Operating state detecting means M7 ... Injection rate calculating means M8 ... Timing control means 1 ... Fuel injection control device 2 ... Diesel engine 3 ... Fuel injection valve (injector) 4 ... Accumulation chamber (common rail) 6 ... Electronic control unit (ECU)

Claims (1)

[Claims] 1. A fuel injection valve for an internal combustion engine, comprising energizing means for supplying a current to a drive solenoid, and switch means for turning on / off a circuit of the drive solenoid, and driving the fuel injection valve to inject fuel. In a fuel injection control device for an internal combustion engine which performs control, an operating state detecting means for detecting an operating state of the internal combustion engine, and an injection rate of the fuel injection valve according to an operating state detected by the operating state detecting means. An injection rate calculation unit to be obtained, a first energization period in which the drive solenoid is energized prior to opening the fuel injection valve, a second energization period in which the fuel injection valve is opened, the first energization period and the second An energization suspension period between the energization period and the second energization period is set according to the injection rate obtained by the injection rate calculation means, and the switch means is driven according to the set value. The fuel injection control device for an internal combustion engine characterized by comprising a timing control means for adjusting the residual magnetic field in the drive solenoid due to energization of said first conduction period at the start timing.