JPH0320583B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection timing control method for a diesel engine, and particularly to a method for controlling engine rotational speed suitable for use in an automobile diesel engine equipped with an intake throttle valve and an electronically controlled fuel injection device. The present invention relates to an improvement in a fuel injection timing control method for a diesel engine, in which the fuel injection timing is determined according to engine operating conditions such as engine load.

Generally, in a diesel engine, the fuel supplied to the combustion chamber is controlled by a fuel injection pump that is driven to rotate in synchronization with the engine rotation. The timing of fuel injection is controlled by using the supply pressure to move a timer and a roller ring, and the amount of fuel injection is controlled by moving a spill ring using a centrifugal governor to change the end of pumping. I try to do that. However, in the past, both the timer and the spill ring were mechanically controlled, making it difficult to precisely control the fuel injection amount.

On the other hand, in recent years, with the development of electronic control technology, especially digital control technology, attempts have been made to electronically control the fuel injection amount of diesel engines.

Such electronic control has a feature that it is possible to inject an optimal amount of fuel at an optimal fuel injection timing depending on engine operating conditions such as engine speed and engine load.

In such electronic control, when the vehicle is decelerating, the spill ring of the fuel injection pump is
Although the system is controlled to a position where no fuel is injected, in reality, the amount of fuel injected does not become completely zero due to leakage of the fuel injection pump or the like. Further, due to variations in parts and changes over time, the amount of leakage injection described above varies greatly. An intake throttle valve that opens and closes in conjunction with the accelerator pedal was added in order to reduce idling vibrations and improve operational feel when the engine is stopped while driving at high altitudes in such conditions. In a diesel engine, even when driving on flat ground, if the intake pressure decreases due to the intake throttle valve being closed, the pressure within the combustion chamber will not rise to the ignition point.
In addition, as the chamber temperature decreases and the ignitability deteriorates, the amount of leaked injection is not combusted and is emitted in large amounts as white smoke, which becomes a harmful component in the exhaust gas.
There were problems such as an increase in HC and generation of a strange odor.

In addition, in order to prevent engine stall when the vehicle decelerates, it is possible to lower the fuel injection amount more slowly than the reduction rate of the required injection amount and provide a so-called dart pot function. When the engine is driving, or in a diesel engine equipped with an intake throttle valve, when the intake throttle valve is closed, even when driving on flat ground, the intake pressure is decreasing. Since a large amount of fuel is injected, unburned fuel is also discharged as white smoke.
Therefore, in the past, there was a problem in that the dart pot could not be used sufficiently to prevent this white smoke.

The present invention has been made to solve the above-mentioned conventional problems, and is capable of preventing the generation of white smoke when the dash pot is in operation. A first object of the present invention is to provide a method for controlling fuel injection timing of an engine.

In addition to the first object, a second object of the present invention is to provide a fuel injection timing control method for a diesel engine that can prevent the generation of white smoke during deceleration.

The present invention relates to a fuel injection timing control method for a diesel engine in which the fuel injection timing is determined according to engine operating conditions such as engine speed and engine load. The middle one achieves the first objective by advancing the fuel injection timing. That is, by advancing the fuel injection timing while the dart pot is operating, ignition performance is improved and combustion is possible even when the air-fuel ratio is lean.
Generation of unburned gas, ie, white smoke, is prevented.

Further, the advance angle amount during the operation of the dart pot is changed in accordance with the fuel injection amount, so that an appropriate advance angle can be achieved.

The present invention also provides a fuel injection timing control method for a diesel engine, as shown in FIG. The purpose has been achieved. In other words, by advancing the ignition timing during deceleration and while the dart pot is operating, ignition performance is improved, combustion is possible even when the air-fuel ratio is lean, and unburned gas is generated, i.e., white smoke. occurrence is prevented.

Further, the advance angle amount during the deceleration is changed in accordance with the engine rotation speed, so that an appropriate advance angle is performed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of an electronically controlled fuel injection device for a diesel engine for automobiles, in which a method for controlling fuel injection timing for a diesel engine according to the present invention is adopted, will be described in detail with reference to the drawings.

In this embodiment, as shown in FIG. 3, a main intake throttle is provided in a main intake passage 12 of a diesel engine 10 and rotates in conjunction with, for example, an accelerator pedal 14 operated by a driver. valve 16;
A sub-intake passage 1 that bypasses the main intake passage 12
8 is a sub-intake throttle valve 20 for reducing idle vibration by throttling intake air during idle.
, a drive shaft 24 that rotates in conjunction with the rotation of the output shaft of the diesel engine 10, and a feed pump 26 for pumping fuel that is fixed to the drive shaft 24 (Fig. 2 shows a state rotated by 90 degrees). ), the fuel pressure adjustment valve 28 for adjusting the fuel supply pressure, and the time required for the drive shaft 24 to rotate by a predetermined crank angle are measured from the rotational displacement of the gear 30 fixed to the drive shaft 24. diesel engine 1
A rotation speed sensor 32 made of, for example, an electromagnetic pickup for detecting the rotation speed of 0, a roller ring 34 for controlling fuel injection timing, and a timer piston 3 for driving the roller ring 34.
6. a timing control valve 38 for controlling the position of the timer piston 36, the timer piston 3;
6, a spill ring 42 for controlling the fuel injection amount, and a plunger 44 for driving the spill ring 42.
a, a spill actuator 44 consisting of a compression spring 44b, a coil 44c and a coil case 44d;
A spill position sensor 4 made of, for example, a variable inductance sensor for detecting the position of the spill ring 42 from the displacement of the plunger 44a.
6. Fuel cut solenoid (hereinafter referred to as FCV) for cutting fuel when the engine is stopped 4
8. A fuel injection pump 22 having a plunger 50 and a delivery valve 52;
an injection nozzle 54 for injecting fuel discharged from the second delivery valve 52 into the auxiliary fuel chamber of the diesel engine 10; and an intake pipe 56.
An intake pressure sensor 58 for detecting the pressure of intake air taken in through the engine, an intake air temperature sensor 60 for similarly detecting the temperature of the intake air, and an intake temperature sensor 60 disposed in the cylinder block 10a of the diesel engine 10. A cooling water temperature sensor 62 for detecting engine cooling water temperature, an accelerator sensor 66 for detecting the depression angle of the accelerator pedal 14 (hereinafter referred to as accelerator opening degree), and an engine detected from the output of the accelerator sensor 66 The target injection timing and calculated injection amount are determined based on the load, the engine rotation speed detected from the output of the rotation speed sensor 32, the engine cooling water temperature detected from the output of the cooling water temperature sensor 62, etc., and the fuel injection pump 22
, an electronic control unit (hereinafter referred to as ECU) 68 that controls the timing control valve 38, spill actuator 44, etc. so that the calculated injection amount of fuel is injected at the target injection timing. In the fuel injection amount control device for the diesel engine 10, the target injection timing is controlled in the ECU 68 during deceleration and when the dart pot is operating.
The angle is advanced in accordance with the calculated injection amount and engine rotational speed.

In the figure, 35 is a cam plate, and 43 is a tension spring.

The ECU 68, as shown in detail in FIG.
A central processing unit (hereinafter referred to as
(referred to as CPU) 69, the output of the cooling water temperature sensor 62 which is input via a buffer 70, and the intake temperature sensor 60 which is input via a buffer 72.
The output of the intake pressure sensor 58 is input via a buffer 74, the output of the accelerator sensor 66 is input via a buffer 76, and the sensor drive frequency signal of the sensor drive circuit 78 output is used to drive the sensor. The timer position sensor is driven by the output of the spill position sensor 46 inputted via the signal detection circuit 80 and the sensor drive frequency signal outputted from the sensor drive circuit 82 and inputted via the sensor signal detection circuit 84. A multiplexer 86 for sequentially taking in 40 outputs, etc.; an analog-to-digital converter (hereinafter referred to as an A/D converter) 88 for converting the analog signal output from the multiplexer 86 into a digital signal;
an input/output port 90 for taking the output of the D converter 88 into the CPU 69; a waveform shaping circuit 94 for shaping the waveform of the output of the rotational speed sensor 32 and taking it into the CPU 69; and a clock generation circuit 102.
A random access memory (hereinafter referred to as RAM) 104 including a backup random access memory (hereinafter referred to as backup RAM) for temporarily storing calculation data etc. in the CPU 69 and which is backed up in the event of a power failure; Read-only memory (hereinafter referred to as ROM) 1 for storing various data, etc.
06, a drive circuit 108 for operating the timing control valve 38 according to the operation result in the CPU 69, a circuit 109 for driving the FCV 48 in accordance with the operation result in the CPU 69, and a digital-to-analog converter. (below,
A servo amplifier 112 and a drive circuit for driving the spill actuator 44 according to the deviation between the output of the CPU 69 and the output of the spill position sensor 46, which are converted into an analog signal by an A/D converter (referred to as an A/D converter) 110. 114.

The action will be explained below.

The control of the fuel injection timing in this embodiment is based on the fifth
The fuel injection timing control routine is executed as shown in the figure. That is, the CPU 69 of the ECU 68
First, in step 1010, the rotational speed sensor 3
From the engine rotational speed NE obtained from the two outputs and the accelerator opening obtained from the output of the accelerator sensor 66, the basic injection timing is determined using, for example, a two-dimensional map stored in the ROM 106.
Find Tbase. Next, the process proceeds to step 1020, where, for example, the accelerator pedal 14 is in a fully closed state,
In addition, since the engine rotational speed NE is equal to or higher than the predetermined value, it is determined whether or not the engine is decelerating. If the determination result is positive, proceed to step 1030;
As shown in the following equation, the final injection timing Tfin is determined by adding, for example, a predetermined advance amount of 3° CA to the basic injection timing Tbase.

Tfin←Tbase＋3゜CA......(1) The predetermined advance amount 3゜CA is the engine rotation speed.
By changing it according to NE, it is possible to obtain a more appropriate advance angle amount.

On the other hand, if the determination result in step 1020 is negative, the process proceeds to step 1040, where the basic injection timing Tbase is directly set as the final injection timing Tfin.

After completing step 1030 or 1040, step
Proceeding to 1050, a dash pot flag is set to increase the amount of fuel when the fuel injection amount is increased more than the required injection amount during deceleration, or when the engine speed decreases by more than a predetermined amount. is set, it is determined whether or not the dart pot is in operation. If the determination result is positive, the process proceeds to step 1060, where the final injection timing Tfin obtained in step 1030 or 1040 is added, for example, by a predetermined advance amount of 5° CA, as shown in the following equation. Then, the final injection timing Tfin is further advanced.

Tfin←Tfin＋5゜CA……(2) The predetermined advance amount added in this step 1060 is
A more appropriate advance angle can be achieved by changing the fuel injection amount.

After step 1060 or the previous step
If the determination result at 1050 is negative, the process proceeds to step 1070, and the timing control valve is adjusted according to the deviation between the final injection timing Tfin and the actual injection timing estimated from the timer position signal output from the timer position sensor 40. The control duty signal to be output to 38 is calculated, and this routine ends.

In this embodiment, not only the advance angle control during the operation of the dart pot but also the advance angle control during deceleration is used, so that the effect of preventing white smoke is particularly high. It is also possible to perform advance angle control during dart pot operation and advance angle control during deceleration, respectively, independently.

In the above embodiments, the present invention was applied to an automobile diesel engine equipped with an intake throttle valve and an electronically controlled fuel injection device, but the scope of application of the present invention is not limited to this, and the present invention is applied to an electronically controlled fuel injection device. It is obvious that the present invention can be similarly applied to an automobile diesel engine equipped with only a fuel injection device or a general diesel engine equipped with other fuel injection devices.

As explained above, according to the present invention, by advancing the fuel injection timing while the dart pot is operating, white smoke is reduced when the dart pot is operating, even on high altitudes and in diesel engines equipped with an intake throttle valve, including on flatlands. can be reduced. Therefore, optimal control can be performed by making full use of the dart pot.
Engine stall can be reliably prevented. Furthermore, by advancing the fuel injection timing not only while the dart pot is operating but also during deceleration,
It has excellent effects such as being able to reduce white smoke during deceleration.

[Brief explanation of the drawing]

1 and 2 are flowcharts showing the gist of the fuel injection timing control method for a diesel engine according to the present invention, and FIG. FIG. 4 is a cross-sectional view, including a partial block diagram, showing the configuration of an electronically controlled fuel injection system for a diesel engine according to an embodiment of the present invention; FIG. 4 is a block diagram showing the configuration of an electronic control unit used in the embodiment; , 5th
Similarly, the figure is a flowchart showing the fuel injection timing control routine. 10... Diesel engine, 16... Main intake throttle valve, 22... Fuel injection pump, 32... Rotational speed sensor, 38... Timing control valve, 40...
...Timer position sensor, 66...Accelerator sensor,
68...Electronic control unit (ECU).

Claims (1)

[Scope of Claims] 1. In a diesel engine fuel injection timing control method in which the fuel injection timing is determined according to engine operating conditions such as engine speed and engine load, the fuel injection timing is advanced while the dart pot is in operation. A fuel injection timing control method for a diesel engine, characterized in that the fuel injection timing is made to be angular. 2. The fuel injection timing control method for a diesel engine according to claim 1, wherein the advance angle amount during the operation of the dart pot is changed in accordance with the fuel injection amount. 3. In a diesel engine fuel injection timing control method in which the fuel injection timing is determined according to engine operating conditions such as engine speed and engine load, the fuel injection timing is advanced during deceleration and when the dart pot is operating. A fuel injection timing control method for a diesel engine, characterized in that: 4. Claim 1, wherein the advance angle amount during deceleration is changed according to the engine rotation speed.
The fuel injection timing control method for a diesel engine as described in .