JP3052572B2 - Fuel injection control device for internal combustion engine - Google Patents

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 that controls the operation of a solenoid-type injector (fuel injection valve) to supply fuel.

[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 an injector of a solenoid valve type,
The injection rate of the injector is uniquely determined by the diameter of the injection nozzle and the injection pressure.

[0003] However, in the diesel engine, generally there is a problem that combustion noise and NO _X due to the ignition delay of the fuel occurs in the injector for injecting at uniquely determined injection rate as described above, Ya noise nO _X of the problem has not been resolved. As a countermeasure, 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 certain period of time for performing normal fuel injection is adopted. In such a 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 at the beginning of fuel injection due to a delay in the rise of the drive current due to the inductance of the coil.
As shown in (a), in addition to the valve-opening current (corresponding to the injection pulse) for normal fuel injection, the high-voltage generator (corresponding to the trigger pulse) simultaneously starts energizing this valve-opening current.
Technology for supplying an exciting current to quickly perform an initial operation of an injector at the start of fuel injection (Japanese Patent Publication No. 49-4524)
No. 8). However, in the case of performing the pilot injection described above, if an attempt is made to improve the initial operation of the injector by this technique, a circuit (see FIG. 14B) for supplying each excitation current at the time of driving the injector twice. A rush current circuit for discharging the energy charged by the capacitor) is required, and there is 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 It is an object to provide a control device.

[0006]

According to the present invention, as shown in FIG. 1, there is provided 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, A switch means M5 for turning on and off a circuit of the drive solenoid M3;
Operating state detecting means M6 for detecting an operating state of the internal combustion engine M1, and an operating state detecting means M for detecting the operating state of the internal combustion engine M1.
6, an injection rate calculating means M7 for obtaining the injection rate of the fuel injection valve M2, and the drive solenoid M3 prior to the opening of the fuel injection valve M2.
A first power supply period during which power is supplied to the fuel injection valve, a second power supply period during which the fuel injection valve M2 is opened, and a power supply suspension period between the first power supply period and the second power supply period.
Is set in accordance with the injection rate determined in step (1), and the switch means (M5) is driven in accordance with the set value, so that the residual force in the drive solenoid (M3) due to energization in the first energization period at the start timing of the second energization period. A fuel injection control device for an internal combustion engine, comprising: timing control means M8 for adjusting a magnetic field.

[0007]

In the fuel injection control device for an internal combustion engine according to the present invention, a 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, the injection rate of the fuel injection valve M2 is obtained by the injection rate calculation means M7 based on the operation state of the internal combustion engine M1 detected by the operation state detection means M6, for example, the rotation speed and load. Furthermore,
The first power supply period, the second power supply period, and the power supply suspension period are set by the timing control means M8 according to the injection rate, and the switch means M5 for turning on and off the circuit of the drive solenoid M3 is driven according to the set values. Then, the on / off timing of the circuit of the drive solenoid M3 is adjusted.

That is, the first power supply period, the second power supply period, and the power supply suspension period can be controlled by adjusting the ON / OFF timing of this circuit by the timing control means M8. It is possible to adjust the residual magnetic field due to energization during the first energization period at the appropriate time. By adjusting the residual magnetic field, it is possible to finely adjust the fuel injection rate at the beginning of the fuel injection.

For example, by the timing control means M8,
As shown in FIG. 2A, by setting the first energization period TP and the energization suspension period TI, as shown in FIG.
The magnetic flux (of the drive solenoid M3) by the first energizing period TP and the magnetic flux by the second energizing period TM are made to partially overlap (that is, at the start timing of the second energizing period TM). Thereby, as shown in FIG. 2C, the lift amount (nozzle lift) of the nozzle of the fuel injection valve M2 increases with a predetermined gradient according to the degree of the overlap of the magnetic fluxes (the degree of the residual magnetic field) (note that the amount of the residual magnetic field) If there is no 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 beginning of fuel injection changes as shown in FIG. 2D according to the nozzle lift.

FIG. 3 shows the relationship between the magnetic flux density and the energization suspension period TI. As the first energization period TP is longer and the energization suspension period TI is shorter, the magnetic flux density is higher, and the fuel injection valve M2 is driven. There is a property that the excitation energy is large. Further, 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 energizing period TP, the second energizing period TM, and the energizing suspension period TI to drive the fuel injection valve M2, thereby providing fuel. By changing the initial injection rate of the injection, suitable control of the fuel injection is realized.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 5 is a schematic configuration diagram illustrating the configuration of the entire fuel injection control device of the embodiment. As shown in the figure, a fuel injection control device 1 of the present embodiment is a pressure accumulating device, and includes a six-cylinder diesel engine 2, a fuel injection valve (injector) 3 for injecting fuel to each cylinder of the diesel engine 2, and An accumulator (common rail) 4 for accumulating high-pressure fuel 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.

The fuel supply pump 5 sucks the fuel stored in the fuel tank 10 through the low-pressure pump 11 according to a control command from the ECU 6, and pressurizes the fuel to a high pressure inside itself. 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 in which high-pressure fuel is stored. Then, by opening and closing an electromagnetic control valve 14 disposed in each injector 3, the high-pressure fuel stored in the common rail 4 is injected into the combustion chamber of each cylinder of the diesel engine 2.

The ECU 6 has an engine speed Ne and an accelerator opening A _CC indicating an engine load detected by a speed sensor 7 and an accelerator sensor 8 as operating state detecting means.
And feedback control of the common rail pressure is performed in order to realize a fuel injection pressure that optimizes the combustion state of the diesel engine 2 in accordance with the detected operating state.

The engine speed Ne and the accelerator opening A, which are detected by the speed sensor 7 and the accelerator sensor 8, respectively.
Based on the _CC , drive control of the control valve 14 of the injector 3 is performed to control fuel injection, which will be described in detail later. The opening / closing operation of the control valve 14 of the injector 3
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 controls the 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, the accelerator sensor 8, and the like. At a predetermined timing based on the detection values of the rotation angle sensor 7 and a cylinder discrimination sensor (not shown).
Output from

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

As shown in FIG.
The power supply terminal 22 has a charging coil L and a switch first transistor T ₁ connected thereto, a constant current circuit 23, a first diode 24, and an injector solenoid 2.
The second transistor T ₂ and are connected in this order for 1 and switch. Further, the downstream side of the coil L and the injector solenoid 21 are connected via second and third diodes 25 and 26, and a capacitor C is connected between the two diodes 25 and 26. Further, 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 / off by the ECU 6 (based on the detected voltage of the capacitor C) so as to keep the charged voltage of the capacitor C constant. A control signal is input. Further, the base terminal B ₂ of the second transistor T ₂ is connected to the ECU
6, an injector drive control signal is input.

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

Next, when the first transistor T ₁ is turned off, a 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 instantaneously from the capacitor C in the direction of arrow c, and gives 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, and gives 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 this embodiment, the second transistor T ₂
By performing the drive control twice, the valve opening current is supplied to the injector solenoid 21 twice. That is, in the first energization, the excitation current and the valve opening current indicated by oblique 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, a control process of the ECU 6 for controlling the driving of the injector 3 using the injector driving circuit 20 will be described with reference to a flowchart of FIG. First,
In step 100, the operating state of the engine 2, such as the engine speed Ne, the accelerator opening A _cc , the cooling water temperature, the intake air temperature, the intake air pressure, etc., is detected based on the output signals from each sensor.

In step 110, based on the detected operating state, the basic injection amount, injection start timing,
Calculate the injection pressure. In the following step 120, based on the engine speed Ne and the accelerator opening A _cc , an injection rate level determination map as shown in FIG. Determine the base level. This 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, 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, an energization start timing TT from a reference position of a predetermined crank angle, a first energization period TP, an energization suspension period (injection suspension period) TI, and a second energization period The period TM is calculated.

Here, each of the timings TT, TP, TI, T
The process of calculating M will be described. The energization start timing TT is set by the following equation (1), where TBASE is a normal injection start signal timing, and TA is a correction set by the level as shown in FIG. Value.

TT = TBASE-TA (1) The first energizing period TP including the energizing current is shown in FIG.
As shown in (b), it is set by the injection rate level and the common rail pressure. In addition, when the common rail pressure is high, a little fuel injection is performed even with a small energization, so that
The first energization period TP is set to be short.

The injection suspension period TI is set by the injection rate level and the common rail pressure as shown in FIG. Note that when the common rail pressure is high, FIG.
Since the first energization period TP is set shorter as shown in FIG. 3B, the energization suspension period TI is set shorter as shown in FIG. 3 in order to obtain a required magnetic flux density.

Second energizing period TM for determining 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 based on each of the timings TT, TP, TI, TM, etc. calculated in the step 140, and this processing is once ended.

[0029] That is, in this embodiment, by the based on the respective timing TT, which is set according to the level, TP, TI, TM, etc., to drive the second transistor T ₂ is a switch, 12 As shown, a desired excitation state by the drive current can be given to the injector 3 before the valve is opened. Thus, 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 according to the operating condition is appropriately selected and easily executed. can do.

Particularly, in the trapezoidal injection according to the present embodiment, an appropriate magnetic flux can be left in the injector solenoid 21 by adjusting the width of the excitation pulse and the injection suspension period. There is a significant effect that it can be changed.

Specifically, for example, as shown in FIG.
Initial fuel injection at idle, low load operation, and high load operation
Period, it is necessary to adjust the cooling water temperature and engine speed Ne
A sharp injection rate can be set,
Engine 2 noise reduction and NO _XCan be reduced
it can.

It should be noted that the present invention is not limited to the above-described embodiment, and can be practiced in various modes without departing from the gist of the present embodiment. For example, a coil L of the embodiment, the first transistor T _1, without using a configuration of the inrush current circuit consisting of capacitor C, by simply adjusting the driving timing of the first transistor T _2, the first conducting period, the (2) The initial injection rate of the injection may be controlled by controlling the power supply period and the power supply suspension period to adjust the residual magnetic field of the injector solenoid 21. In this embodiment, the same effects as those of the above embodiment can be obtained, and there is an advantage that the configuration is simplified.

[0033]

As described in detail above, in the fuel injection control apparatus for an internal combustion engine of the present invention, the timing control means
By adjusting the first energizing period, the second energizing period, and the energizing suspension period to drive the fuel injection valve, the initial injection rate of the fuel injection can be changed. It can be performed. As a result, with a simple apparatus configuration, a marked effect of realizing a reduction of reduction and NO _X of noise emitted from a diesel engine.

[Brief description of the 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 a relationship between a magnetic flux density and a first energization period and an energization suspension period.

FIG. 4 is a graph showing a relationship between a valve opening time and a 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 illustrating a control process of the injector according to the 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 a relationship between a level and an energization period.

FIG. 11 is a graph showing a relationship between an injection amount and a 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 operation 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 detection means M7 ... injection rate calculation means M8 ... timing control means 1 ... fuel injection control device 2 ... diesel engine 3 ... Fuel injection valve (injector) 4 ... Pressure accumulation chamber (common rail) 6 ... Electronic control unit (ECU)

Continuation of the front page (56) References JP-A 61-120051 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02D 41/20 330 F02D 41/40 F02M 45/08

Claims (1)

(57) [Claims] The present invention comprises: an energizing means for supplying a current to a drive solenoid of a fuel injection valve of an internal combustion engine; and a switch means for turning on and off a circuit of the drive solenoid. In a fuel injection control device for an internal combustion engine that performs control, operating state detection means for detecting an operation state of the internal combustion engine, and an injection rate of the fuel injection valve according to an operation state detected by the operation state detection means Means for calculating an injection rate to be determined; a first energizing period for energizing the drive solenoid prior to opening of the fuel injection valve; a second energizing period for opening the fuel injection valve; An energization suspension period between the energization period and an injection rate calculated by the injection rate calculation unit, and the switch unit is driven in accordance with the set value to perform the second energization period. 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.