JPH0522064B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an ignition timing feedback control method for an electronically controlled diesel engine, and is particularly suitable for use in an electronically controlled diesel engine for automobiles equipped with an ignition sensor. The present invention relates to an improvement in an ignition timing feedback control method for an electronically controlled diesel engine, in which the fuel injection timing is feedback-controlled so as to match the required ignition timing determined according to the engine operating state.

[Prior art]

When controlling fuel injection timing to optimize the exhaust gas purification performance of diesel engines, especially automotive diesel engines, the applicant has already installed ignition sensors such as flame sensors in the combustion chamber in Japanese Patent Application Laid-Open No. 58-192935. However, by feeding back the detection results of the ignition timing in the combustion chamber (the timing when the pressure in the cylinder rises rapidly due to combustion) by the ignition sensor, the measured ignition timing can be determined by the accelerator opening degree, engine speed, etc. It is proposed to perform feedback control of fuel injection timing to match the ignition timing. According to such feedback control of the fuel injection timing based on the output of the ignition sensor, it is possible to accurately control the fuel injection timing after combustion of the air-fuel mixture has started. When starting the engine, when combustion has not yet started and an ignition signal cannot be detected, injection timing control using feedback control cannot be performed, resulting in poor engine startability, especially at low temperatures. .

[Purpose of the invention]

The present invention has been made to solve the above-mentioned conventional problems, and it is possible to accurately determine when an engine is started when no ignition signal is detected, and to obtain an appropriate fuel injection timing even when the engine is started. Therefore, an object of the present invention is to provide an ignition timing feedback control method for an electronically controlled diesel engine, which improves engine startability particularly at low temperatures.

[Structure of the invention]

The present invention provides ignition timing for an electronically controlled diesel engine that performs feedback control of fuel injection timing so that the measured ignition timing detected from the engine combustion state matches the required ignition timing determined according to the engine operating state. In the feedback control method, as shown in Fig. 1,
The measured ignition timing is not within the set range, so it is determined whether the engine is starting or not. If the engine is starting, the fuel injection timing is fixed at the advanced setting value. The above object is achieved by including the step of feedback controlling the fuel injection timing so that the measured ignition timing matches the required ignition timing when the engine is not starting. Further, in an embodiment of the present invention, the set value is set as the fuel injection timing at which ignition occurs at top dead center, thereby reliably improving engine startability. Further, in another embodiment of the present invention, the setting value is
The engine startability is further improved by changing the temperature according to the engine cooling water temperature.

[Action of the invention]

In the present invention, since it is not within the set range of the measured ignition timing, it is determined whether or not it is time to start the engine, so that it is possible to accurately determine whether it is time to start the engine. Furthermore, since the fuel injection timing is fixed at the set value on the advance side when starting the engine determined in this way, it is possible to sufficiently advance the fuel injection timing even when starting the engine when no ignition signal can be detected. , engine startability is improved.

【Example】

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an electronically controlled diesel engine for automobiles equipped with an ignition sensor and employing an ignition timing feedback control method according to the present invention will be described in detail below with reference to the drawings. As shown in FIG. 2, this embodiment includes a drive shaft 14 that rotates in conjunction with the rotation of the output shaft of a diesel engine 10, and a feed pump 1 fixed to the drive shaft 14 for pumping fuel.
6 (FIG. 2 shows the state unfolded at 90 degrees), a fuel pressure adjustment valve 18 for adjusting the fuel supply pressure, and a rotational displacement of a gear 20 fixed to the drive shaft 14 to cause the drive shaft 14 to move to a predetermined crank position. To drive the pump plunger 40 in cooperation with a rotation speed sensor 22 consisting of an electromagnetic pickup, for example, and a face cam 23 for measuring the time required to rotate by an angle and detecting the rotation speed Ne of the diesel engine 10. a roller ring 24, and a timer piston 26 for controlling the rotational position of the roller ring 24.
(FIG. 2 shows the 90° unfolded state), a timing control valve 28 for controlling the fuel injection timing by controlling the position of the timer piston 26;
a spill ring 32 for controlling the timing of fuel release from the pump plunger 40, and the spill ring 3;
a spill actuator 34 for controlling the fuel injection amount by controlling the position of the spill actuator 34;
For example, a fuel injection pump having a spill position sensor 36 consisting of a variable inductance sensor, a fuel cut solenoid (hereinafter referred to as FCV) 38 for cutting fuel when the engine is stopped, and a delivery valve 42 for preventing backflow or dripping of fuel. 12, an injection nozzle 44 for injecting the fuel discharged from the delivery valve 42 of the fuel injection pump 12 into the combustion chamber 10A of the diesel engine 10, and intake air taken in through the intake pipe 46. an intake temperature sensor 50 for detecting the temperature of the cylinder block 1 of the diesel engine 10;
A water temperature sensor 51 disposed at 0B for detecting the engine cooling water temperature, and a top dead center sensor 52 for detecting that the rotation angle of the diesel engine 10 has reached a predetermined value, for example, the top dead center TDC. , an accelerator sensor 54 for detecting the depression angle of the accelerator pedal 53 operated by the driver (hereinafter referred to as accelerator opening degree); an ignition sensor 56 for receiving combustion light in the engine combustion chamber 10A; and the accelerator. The required injection timing and required injection amount are determined from the accelerator opening Accp detected from the output of the sensor 54, the engine rotation speed Ne detected from the output of the rotation speed sensor 22, etc., and the required injection timing is determined from the fuel injection pump 12. the timing control valve 28 so that the required injection amount of fuel is injected;
It is comprised of an electronic control unit (hereinafter referred to as ECU) 58 that controls the spill actuator 34 and the like. As shown in detail in FIGS. 3 and 4, the ignition sensor 56 is inserted and fixed into the cylinder head 10C of the diesel engine 10, for example, in a case 56A that is shared with a glow plug case, and in the center of the case 56A. an inserted light guide 56B, for example made of quartz glass, for transmitting combustion light;
and a light receiving element 56C made of, for example, a silicon photodiode, for detecting the light transmitted by the light guide 56B and converting it into an electrical signal.
It is composed of and. The ECU 58, as shown in detail in FIG.
A central processing unit (hereinafter referred to as CPU) 58A for performing various calculation processes, a read-only memory (hereinafter referred to as ROM) 58B for storing control programs and various data, etc.;
A random access memory (hereinafter referred to as RAM) 58C for temporarily storing calculation data etc. in A, a clock generation circuit 58D, the output of the spill position sensor 36 inputted via a buffer 58E, and a buffer 58F. A multiplexer (hereinafter referred to as MPX) for sequentially taking in the output of the intake air temperature sensor 50 which is input via the buffer 58G, the output of the water temperature sensor 51 which is input via the buffer 58G, the output of the accelerator sensor 54 which is input via the buffer 58H, etc. ) 58K and the MPX58
An analog-to-digital converter (hereinafter referred to as an A/D converter) 58L for converting the analog signal of the K output into a digital signal, and the A/D converter 58L
An input/output port (hereinafter referred to as I/O port) 58M for taking the output into the CPU 58A, and a waveform shaping of the output of the ignition sensor 56 to the CPU 5
Waveform shaping circuit 58N for direct input to 8A
Then, the output of the rotation speed sensor 22 is waveform-shaped.
A waveform shaping circuit 58P for directly importing the output into the CPU 58A, a waveform shaping circuit 58Q for shaping the waveform of the top dead center sensor 52 output and directly importing it into the CPU 58A, and a waveform shaping circuit 58Q for directly importing the output from the top dead center sensor 52 into the CPU 58A. The CPU 58A is converted into an analog signal by a drive circuit 58R for driving the CPU 58R and a digital-to-analog converter (hereinafter referred to as a D/A converter) 58S.
According to the deviation between the output and the spill position signal output from the spill position sensor 36, a servo amplifier 58T and a drive circuit 58U for driving the spill actuator 34 and each of the component devices are connected to transmit data and data. Common bus 5 for transferring instructions
It is composed of 8V. The operation of the embodiment will be explained below. The ignition timing feedback control in this embodiment is executed according to the flowcharts shown in FIGS. 6 and 7. That is, for example, when the power switch is turned on, the steps of the initial setting routine shown in FIG.
Proceeding to step 110, for example, the duty control signal Duty of the timing control valve 28 is set to 0%, and the initial setting value of the fuel injection timing is set to a value on the advance side where ignition is performed at the top dead center. On the other hand, ignition timing feedback control according to engine operating conditions is executed according to a routine in the main program as shown in FIG. That is, first, in step 210, the timing control valve 28
It is determined whether the time required for driving the drive timing, for example, 50 milliseconds, has elapsed. If the determination result is positive, the process proceeds to step 212, where the engine rotation speed determined from the output of the rotation speed sensor 22 is determined.
The engine load Load detected from Ne and the accelerator opening degree output from the accelerator sensor 54 is read.
Next, the process proceeds to step 214, where, for example, the ROM5
Using the two-dimensional map stored in advance in 8B, the required ignition timing Tfire is determined according to the engine speed Ne and the engine load Load. Next, the process proceeds to step 216, where, for example, the measured ignition timing is determined from the rising edge of the waveform shaping signal output from the ignition sensor 56.
Detect T′fire. Next, proceed to step 218 to measure the ignition timing.
It is determined whether the absolute value of T′fire is less than a set range, for example, 100° CA. If the determination result is positive, that is, if it is determined that there is no problem in performing feedback control based on the measured ignition timing T'fire rather than at the time of engine start when no ignition signal is detected, the process proceeds to step 220, and the following equation is used. According to
The difference ΔTfire between the required ignition timing Tfire and the measured ignition timing T′fire is determined. ΔTfire=Tfire−T'fire...(1) Next, the process proceeds to step 222, where the proportional term D(p) and integral term D(i) of the drive duty signal of the timing control valve 28 are calculated as the difference ΔTfire, as shown in the following equation. Find it as a function. D(p)=f(ΔTfire)...(2) D(i)=g(ΔTfire)...(3) Next, proceed to step 224, and as shown in the following equation,
The duty control signal Duty is determined as the sum of the proportional term D(p) and the integrated value 〓D(i) of the integral term. Duty=D(p)+〓D(i)...(4) After step 224 or the previous step
If the determination result in step 218 is negative, and it is determined that the engine is starting when no ignition signal is detected, the process proceeds to step 226, and the current or previous duty control signal (the initial setting value is 0% when starting the engine) is detected. An output corresponding to the duty is given to the timing control valve 28 to drive the timer piston 26 and control the fuel injection timing. After step 226 or the previous step
If the determination result at 210 is negative, this routine exits. In this embodiment, it is determined that the engine is starting from the fact that the measured ignition timing T'fire is not within the set range, that is, the value that the measured ignition timing never achieves, ±100℃A. , it is possible to easily determine that it is time to start the engine. In addition, in this embodiment, the fixed injection timing at the time of engine startup is set to a set value that causes ignition to occur at top dead center;
That is, since the duty control signal Duty is set to 0%, the engine startability is particularly excellent. Note that the set value is not limited to this, and it is also possible to set it to a constant value other than the duty control signal Duty = 0%, or to change it according to the engine cooling water temperature as shown in Fig. 8. . In the latter case, engine startability is further improved.

【Effect of the invention】

As explained above, according to the present invention, it is possible to accurately determine when the engine is started when no ignition signal is detected, and to obtain an appropriate fuel injection timing even when the engine is started. It has the excellent effect of improving engine startability at low temperatures.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing the gist of the ignition timing feedback control method for an electronically controlled diesel engine according to the present invention, and FIG.
A cross-sectional view, including a partial block diagram, showing the configuration of an embodiment of an electronically controlled diesel engine for automobiles;
FIG. 3 is an enlarged cross-sectional view showing the structure of the ignition sensor used in the embodiment, FIG. 4 is an enlarged cross-sectional view showing the ignition sensor installed in the engine, and FIG. Block diagram showing the configuration of the electronic control unit used in the example, No. 6
Similarly, FIG. 7 is a flowchart showing the main part of the routine for initializing the fuel injection timing, FIG. 7 is a flowchart showing the main part of the routine for feedback controlling the ignition timing, and FIG. FIG. 7 is a diagram showing an example of the relationship between the engine cooling water temperature and the initial setting value (fixed injection timing) of the duty control signal in a modification of the present invention. DESCRIPTION OF SYMBOLS 10... Diesel engine, 12... Fuel injection pump, 26... Timer piston, 28... Timing control valve, 40... Pump plunger, 44... Injection nozzle, 53... Accelerator pedal, 54
...Accelerator sensor, 56...Ignition sensor, 58...Electronic control unit (ECU), Tfire...Required ignition timing,
T′fire…Measured ignition timing.

Claims (1)

[Scope of Claims] 1. An electronically controlled diesel engine that performs feedback control on fuel injection timing so that the measured ignition timing detected from the engine combustion state matches the required ignition timing determined according to the engine operating state. In the ignition timing feedback control method of ignition of an electronically controlled diesel engine, comprising: a step of feedback controlling the fuel injection timing so that the measured ignition timing matches the requested ignition timing when the engine is not starting; Timing feedback control method. 2. The ignition timing feedback control method for an electronically controlled diesel engine according to claim 1, wherein the set value is a fuel injection timing at which ignition occurs at top dead center. 3. The ignition timing feedback control method for an electronically controlled diesel engine according to claim 1, wherein the set value is changed in accordance with engine cooling water temperature.