JPH09151772A - Fuel injection control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent increase of a fuel injection amount and deterioration of emission due to decrease of a nozzle valve opening pressure. SOLUTION: In a split injection amount control means, a fuel injection valve 16 provided with a valve element action detection means detecting opening/ closing action of a valve element like a nozzle lift sensor is used, and also the valve element of the fuel injection valve 16 performs target opening/closing action with valve open timing detected by the valve element action detection means serving as split injection timing, and a spill valve 18 and a hydraulic control valve 27 are controlled by the lapse of time from the split injection timing or a rotational angle of a fuel injection pump 1 so that each of the split injection period, split interval and main injection period obtains an optimum value. The split injection amount control means is provided in an electronic control device 5.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a fuel injection control device for a diesel engine.

[0002]

2. Description of the Related Art In a diesel engine, split (or pilot) injection is performed prior to main injection in order to reduce harmful components (NO _x etc.) and noise in exhaust gas.

However, a fuel injection valve generally used in a diesel engine is provided with a valve body biased in a valve closing direction by a spring, and the pressure of fuel sent from a fuel injection pump is equal to that of the spring. When it becomes larger than the biasing force, the valve body moves to the valve opening position to inject fuel. This fuel injection valve operates independently of the electromagnetic spill valve, and when the biasing force of the spring of the fuel injection valve decreases with time, the valve opening pressure of the valve element decreases. Therefore, if the oil feeding characteristic from the fuel injection pump does not change, the fuel injection valve is opened earlier and closed later, and the fuel injection amount is increased accordingly (see FIG. 3). ).

The change over time in the valve opening pressure of the fuel injection valve is generally several percent to 20% under certain conditions. Under such conditions, even if the split (pilot) injection amount is optimally adjusted initially. The injection amount greatly increases over time, and the exhaust emission becomes significantly worse. Furthermore, it is unlikely that the opening pressure of the fuel injection valve provided for each cylinder of the multi-cylinder engine will uniformly decrease, and
Considering the initial product tolerance, it is very difficult to make split injection have the same characteristics in all cylinders.

Therefore, in the invention disclosed in Japanese Patent Laid-Open No. 4-175438, the fuel injection device is provided with a valve body biased in the valve closing direction by a spring, and when the fuel pressure becomes larger than the biasing force of the spring. A fuel injection valve that opens a valve body to inject fuel, a fuel injection pump that supplies high-pressure fuel to the fuel injection valve in a pressure delivery stroke, and a high pressure to the fuel injection valve in a pressure delivery stroke of the fuel injection pump. Pressure adjusting means for adjusting the fuel pressure to cause the split injection by the fuel injection valve, and split injection by controlling the pressure adjusting means so that the valve body of the fuel injection valve performs a target opening / closing operation. By means of split injection control means, valve body operation detection means for detecting the operation of the valve body of the fuel injection valve, and the valve body operation detection means at the time of split injection The difference between the actual opening / closing operation of the valve body of the fuel injection valve and the target opening / closing operation of the valve body of the fuel injection valve by the split injection control means is caused by the pressure adjusting means from the next time on the split injection control means. The above problem is to be solved by providing a correction control means for reflecting the above control.

[0006]

However, the correction by the fuel injection control device disclosed in Japanese Patent Laid-Open No. 4-175438 can prevent an increase in the fuel injection amount due to a decrease in the nozzle opening pressure, but By performing the correction, the split interval becomes shorter than before the decrease in the nozzle opening pressure, so that there is a problem that the emission deteriorates as shown in FIG. It is an object of the present invention to further improve the above-mentioned conventional technique and prevent deterioration of emission due to such reasons.

[0007]

Therefore, the present invention utilizes a means for detecting the valve body operation of a fuel injection valve, and at the same time, the split injection timing, split injection period and split interval are maintained even when the nozzle opening pressure decreases. , And a means for controlling each of the main injection periods to optimal values are provided to prevent an increase in the fuel injection amount due to a decrease in the nozzle opening pressure and a deterioration in emissions.

According to a first aspect of the present invention, the control by the split injection amount control means for controlling the pressure adjusting means of the fuel injection control device is performed by splitting the split injection period, the split interval, and the main injection period. It is characterized in that it is performed according to the elapsed time from the injection timing.

Further, according to the second aspect of the present invention, similarly, the control by the split injection amount control means for controlling the pressure adjusting means of the fuel injection control device is performed in the split injection period, the split interval, and the main injection period. Each of them is characterized in that the phase of the fuel injection pump is changed from the split injection timing, that is, by the rotation angle.

Further, the invention according to claim 3 is the fuel injection control device according to claim 1 or claim 2, wherein an actual valve opening operation of the valve element of the fuel injection valve at the time of split injection during idle stabilization is performed. A feature is that an idle learning control means for correcting the target valve opening operation from the deviation amount from the target valve opening operation of the fuel injection valve by the split injection amount control means is provided.

By implementing the present invention, the method of claim 1
In any of the cases described in (1) to (3), each of the split injection timing, the split injection period, and the split interval can be always set to the optimum value with respect to the engine speed and the accelerator opening. Even if the nozzle valve opening pressure is reduced, it is possible to prevent the emission from deteriorating.

[0012]

Next, an embodiment of the present invention will be described with reference to the drawings. The present invention is applied to a distributed type fuel injection pump, and the method of pumping the fuel may be either face cam pressure feeding or inner cam pressure feeding. Therefore, the face cam pressure feeding method will be described as an example. Further, since the embodiment of the present invention described here is an improvement of the conventional electronically controlled fuel injection pump, the description will be made in the order of the description before the improvement and after the improvement. An embodiment of the present invention will be described.

First, a conventional face cam pressure feed type distribution type fuel injection pump 1 and a controller 5 shown in FIG.
Will be described. The drive shaft 2 is rotationally driven by an engine (not shown) in synchronization with one half of the engine speed. A signal rotor 3 is coaxially attached to the drive shaft 2, and a plurality of convex teeth are formed on the outer periphery of the signal rotor 3. Reference numeral 4 denotes a rotation speed sensor, which faces the outer periphery of the signal rotor 3, generates a pulse signal according to the engine rotation speed by electromagnetic induction of the convex teeth of the signal rotor 3, and outputs it to the electronic control unit 5. To do.

The convex teeth on the outer periphery of the signal rotor 3 are closely spaced with a small tooth portion A, and a large spacing is 2
And a tooth portion B formed in a set. The tooth portions B are formed at equal intervals as many as the number of cylinders (every 90 ° for 4 cylinders, every 60 ° for 6 cylinders). A face cam 7 for driving a plunger 6 for pumping fuel and a vane pump 8 as a fuel feed pump are connected to the drive shaft 2. The face cam 7 is integrated with the plunger 6 and is pressed against a roller 11 provided on the roller ring 10 by a spring 9.

Therefore, when the face cam 7 is rotationally driven by the drive shaft 2, the convex portion of the face cam 7 rides on the roller 11, and the face cam 7 itself and the plunger 6 integrated with it are rotated. Along with this, the plunger 6 reciprocates in the axial direction. Since the plunger 6 is inserted into the cylinder bore 12a of the pump cylinder 12 and forms the pressure chamber 13 at the tip thereof, the volume of the pressure chamber 13 is expanded or contracted by the component of the reciprocating motion of the plunger 6, and at the same time the rotational motion A port on the suction side and a port on the discharge side opening to the pressure chamber 13 are switched depending on the component and communicate with each other. Feed pump 8
The pressurized fuel discharged from the discharge port 14 is stored in the fuel chamber 15, but the fuel is sucked into the pressure chamber 13, pressurized to a high pressure, and pumped to the fuel injection valve 16 at a predetermined timing. Then, the fuel is injected into the fuel chamber of the engine (not shown).

A spill valve 18 for releasing the pressure in the pressure chamber 13 is provided in the housing 17 of the fuel injection pump 1. By opening and closing the spill valve 18 by the electronic control unit 5, the fuel injection start timing and The injection amount and injection rate can be controlled. The cylindrical outer peripheral surface 10a of the roller ring 10 can rotate within a predetermined angle range about the axis of the drive shaft 2. The rotation causes the position of the roller 11 to move in the rotation direction, so that the timing at which the convex portion of the face cam 7 rides on the roller 11 changes, and thereby the fuel injection timing can be changed. In order to rotate the roller ring 10, a slide pin 19 extends downward from the roller ring 10 in FIG. 2, and its lower end reciprocally slides left and right in a timer cylinder 20 formed in the housing 17. Is engaged with a timer piston 21 which is fitted so that

In FIG. 2, the timer high-pressure chamber 22 on the right side of the timer piston 21 communicates with the fuel chamber 15 via the throttle 23, and receives the fuel pressurized by the feed pump 8. The oil pressure pushes the timer piston 21 to the left, but in opposition to that, the timer piston 2
The timer spring 2 is provided in the timer low-pressure chamber 24 on the left side of 1.
5 is attached. The timer low-pressure chamber 24 communicates with the suction port 26 of the feed pump 8 and is always at a low pressure during operation. The hydraulic pressure of the fuel acting on the timer high-pressure chamber 22, that is, the supply pressure, varies greatly in relation to the engine speed, and thus the speed of the drive shaft 2. When the timer piston 21 moves to a position where the balance is established, and the rotation of the roller ring 10 is adjusted via the slide pin 19, the fuel injection timing changes according to the engine speed.

The hydraulic pressure of the timer high pressure chamber 22 is the same as that of the timer high pressure chamber 2.
2 and the timer low-pressure chamber 24, a hydraulic control valve 27 formed of an electromagnetic valve is inserted, and by electrically connecting the hydraulic control valve 27 to the electronic control unit 5 to control opening and closing,
The hydraulic pressure in the timer high pressure chamber 22 is partially converted to the timer low pressure chamber 24.
The position of the timer piston 21 and the rotational position of the roller ring 10 are changed to control the fuel injection timing.

As described above, the timer device 28 of the face cam pressure feed type distribution type fuel injection pump 1 shown in FIG.
It comprises a timer cylinder 20, a timer piston 21, a roller ring 10 interlocking with the timer piston 21, a hydraulic control valve 27 for controlling the position of the timer piston 21, and the like. Note that the drive shaft 2 and the timer piston 21 are drawn in parallel in FIG. 2 for easy understanding, but the latter is in a direction perpendicular to the former in order to operate as described above. Crosses Similarly, the axis of the feed pump 8 is also 90 ° with respect to the drive shaft 2.
It is drawn rotated.

The rotation speed sensor 4 is composed of the roller ring 1
It is carried on the outer peripheral surface 10a of No. 0, and its output signal is inputted to the electronic control unit 5, but the control unit 5 also has a top dead center indicated as a TDC signal from the engine as shown in FIG. A point signal, an accelerator opening signal indicating the magnitude of the load on the engine, an output signal from a water temperature sensor detecting a cooling water temperature, etc. are input.

The control of the valve closing timing and valve opening timing of the spill valve 18 is controlled by the angle with reference to the toothless portion of the tooth portion B described above. Specifically, the command value is the number of toothless portions of the tooth portion A. The calculation is performed in the form of + surplus angle, and the surplus angle is converted into time for control.
As shown in FIG. 5, control of the timer device 28 is performed by a TDC signal from the engine (rotational position signal on the engine side) and a portion corresponding to the tooth B of the signal from the rotation speed sensor 4 of the pump (rotational position signal on the pump side). The phase difference of is constantly measured.
Then, the hydraulic control valve 27, which is the timer control valve (TCV), is controlled so that the phase difference matches the timer command value.

Further, at the time of idling, as shown in FIG. 6, control for correcting the injection amount of each cylinder, that is, the command value of the opening timing of the spill valve 18 so that the maximum rotation speed of each cylinder becomes its average value. The non-uniform amount compensation control is performed. Specifically, it detects the rotation speed of each explosion of each cylinder of the engine,
The rotation speed of each cylinder is obtained by detecting the time required to move a certain fixed angle, that is, the interval between two teeth of the signal rotor, and compared with the rotation speed average value of all cylinders. The injection amount, that is, the command value of the spill valve opening timing is corrected for each cylinder.

An embodiment of the present invention after improvement is shown in FIG.
In this embodiment, one of the input signals to the electronic control unit 5
As an example, the output signal of the nozzle lift sensor of the nozzle 16b is added. Since the other points are almost the same as those of the fuel injection pump 1 shown in FIG. 2, the description of the overlapping portions will be omitted. Hereinafter, a case where an eddy current is used as the detection means of the signal of the nozzle lift sensor will be described, but a piezoelectric element, a strain gauge, or the like may be used as another detection means.

The control method of this embodiment will be described with reference to FIG. As the split injection timing S, the nozzle opening signal output from the nozzle lift sensor provided in the nozzle b is applied, and as shown in FIG. 7A, the split injection period A, the split interval B, the main The injection period C is controlled by applying the elapsed time from the split injection timing S, respectively. The split injection timing S is controlled by controlling the hydraulic control valve 27 which is the timing control valve of the timer device 28.

In FIG. 7 (b), (1) shows target injection timings, injection periods, and split intervals for split injection and main injection. The state where the valve pressure is lowered and the split injection timing S is deviated is illustrated in (2).
As the control in such a case, first, as shown in (3), control is performed so that all of the split injection period A, the split interval B, and the main injection period C are the same as the case of the target value (1). . As a result, the entire injection pattern is advanced, and as shown in (4), the split injection timing S is controlled to match the target value to retard the entire injection pattern to obtain the target (1 ) State.

Next, a control method as another embodiment of the present invention will be described with reference to FIG. In this case as well, the split injection timing S is the nozzle opening signal output by the nozzle lift sensor provided in the nozzle 16b, but the split injection period A, the split interval B, and the main injection period C are used.
Are controlled by applying the rotation angle from the split injection timing S, for example, the number of convex teeth formed on the outer circumference of the signal rotor 3 in the pump 1.

As shown in FIG. 9, a concrete command value is calculated so as to have a shape of the number of missing teeth of the tooth portion A + a surplus angle, and the surplus angle is converted into time for control.

In more detail, the split injection timing S, the split injection period A, the split interval B, and the main injection period C will be described in this order with reference to FIG. For the split injection timing S, a signal output from a nozzle lift sensor provided in the nozzle 16b is used as a nozzle opening signal, and the timer device 28 is controlled under each operating condition as shown in FIG. The nozzle opening pressure decrease amount is estimated based on the valve signal and the deviation amount of the target valve opening timing calculated from the two-dimensional map A of the engine speed and the accelerator opening (not shown), and the amount corresponding to the decrease amount is not shown in the figure. The entire control map B of the target split injection timing calculated from the two-dimensional map B of the engine speed and the accelerator opening is corrected, and the hydraulic control valve 27, which is a timer control valve, is controlled so that the split injection timing is always optimum. By doing.

Since the split injection period S, split interval B, and main injection period C are stored in the electronic control unit 5, they are calculated from two-dimensional maps C, D, E of engine speed and accelerator opening (not shown). The spill valve 18 is controlled so that the spill valve 18 has a predetermined value. At this time, in controlling the spill valve 18, it is necessary to consider a delay due to the length of the injected steel pipe.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating the overall configuration of a fuel injection control device as an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating the overall configuration of a conventional fuel injection control device.

FIG. 3 is a diagram for explaining a problem of the conventional technique.

FIG. 4 is a diagram for explaining a problem of the conventional technique.

FIG. 5 is a diagram for explaining the operation of the embodiment of the present invention.

FIG. 6 is a diagram for explaining the operation of the embodiment of the present invention.

FIG. 7A and FIG. 7B are diagrams for explaining the operation of one embodiment of the present invention.

FIG. 8 is a diagram for explaining the operation of another embodiment of the present invention.

FIG. 9 is a diagram for specifically explaining the operation of another embodiment of the present invention.

FIG. 10 is a diagram for specifically explaining the operation of the embodiment of the present invention.

[Explanation of symbols]

 1 ... Fuel injection pump 2 ... Drive shaft 3 ... Signal rotor 5 ... Electronic control device 6 ... Plunger 7 ... Face cam 8 ... Feed pump 10 ... Roller ring 11 ... Roller 13 ... Pressure chamber 14 ... Rotation speed sensor 15 ... Fuel chamber 16 ... Fuel injection valve 16b ... Nozzle (including nozzle lift sensor) 18 ... Spill valve 19 ... Slide piston 20 ... Timer cylinder 21 ... Timer piston 22 ... Timer high pressure chamber 24 ... Timer low pressure chamber 25 ... Timer spring 27 ... Hydraulic control valve 28 ... Timer device

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location F02M 41/12 330 F02M 41/12 330F 350 350A

Claims (3)

[Claims] 1. A valve body is biased in a valve closing direction by a spring, and when the pressure of the supplied fuel becomes larger than the biasing force of the spring, the valve body moves to a valve opening position to inject fuel. A fuel injection valve that supplies high-pressure fuel to the fuel injection valve during a pressure-feeding stroke, and the pressure of high-pressure fuel that is supplied to the fuel injection valve during a pressure-feeding stroke of the fuel injection pump Pressure adjusting means for performing split injection by the fuel injection valve, valve body operation detecting means for detecting operation of the valve body of the fuel injection valve, and split injection timing as valve opening timing of the valve body operation detecting means When the split injection is performed during the split injection period, the split interval, and the main injection period so that the valve body of the fuel injection valve performs a target opening / closing operation. The fuel injection control apparatus characterized by comprising a split injection amount control means for controlling the time from. 2. A valve body urged in a valve closing direction by a spring, and when the pressure of the supplied fuel becomes larger than the urging force of the spring, the valve body moves to a valve opening position to inject fuel. A fuel injection valve that supplies high-pressure fuel to the fuel injection valve during a pressure-feeding stroke, and the pressure of high-pressure fuel that is supplied to the fuel injection valve during a pressure-feeding stroke of the fuel injection pump Pressure adjusting means for performing split injection by the fuel injection valve, valve body operation detecting means for detecting operation of the valve body of the fuel injection valve, and split injection timing as valve opening timing of the valve body operation detecting means When the split injection is performed during the split injection period, the split interval, and the main injection period so that the valve body of the fuel injection valve performs a target opening / closing operation. The fuel injection control apparatus characterized by comprising a split injection quantity means for controlling the angle from. 3. A deviation amount between an actual valve opening operation of the valve element of the fuel injection valve at the time of split injection when the idling is stable and a target valve opening operation of the fuel injection valve by the split injection amount control means. 3. The fuel injection control device according to claim 1 or 2, further comprising idle learning control means for correcting the target valve opening operation.