JPS61277845A - Fuel injection control method for internal-combustion engine - Google Patents

Abstract

PURPOSE:To stabilize engine rotation by detecting the load condition from predetermined crank angle position after opening of intake valve under idle operation then operating and feeding fuel accordingly. CONSTITUTION:On the basis of crank angle signal T24 to be fed from crank angle sensor 16 immediately after production of TDC signal T04 from TDC sensor 15, first stage #0 and following stages in crank angle positions (stages) defined into six between respective TDC position are detected. During this process, it is decided whether the engine is idling by means of an absolute pressure transducer 5 in the intake tube. Quantity of fuel corresponding with the load condition is operated in stage #0 corresponding with the condition after opening of intake valve if it is under idle operation while operated in stage #3 corresponding with the condition prior to opening of intake valve if it is not idle operation thus to feed a corresponding drive signal to fuel injection valve 8.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a fuel injection control method for an internal combustion engine, and more particularly to a fuel injection control method for controlling fuel injection timing according to operating conditions.

(Technical background of the invention and its problems) Fuel injection control that uses fuel injection valves to inject and supply fuel to an internal combustion engine is based on various parameters representing the operating state of the engine, such as engine speed and absolute pressure in the intake pipe. ,
Based on the throttle valve opening degree, 02 concentration in exhaust gas, etc., the amount of injected fuel is calculated according to the operating state of the engine, that is, the opening time of the fuel injection valve, and the fuel injection valve is opened for the calculated opening time. Conventionally, the opening timing of the fuel injection valve is set at a predetermined crank angle position before the intake valve opens regardless of the engine operating state, that is, at a predetermined crank angle position before the transition from the exhaust stroke to the intake stroke. The angle position was controlled.

For example, the amount of fuel is increased under various conditions, such as during warm-up, high-load operation, or startup.

The entire amount of fuel needs to be drawn into the cylinder by the end of the intake stroke, and the air flow velocity when the throttle valve is open is high when the intake valve is open. The high air velocity at the time of the valve opening promotes evaporation and atomization of the fuel adhering to the intake pipe wall, creating a good mixture of air and fuel within the cylinder, so fuel injection begins before the intake valve opens. No particular problem will occur if this is done.

However, even during normal idling, if fuel injection is started before the intake valve opens, the throttle valve opening is at the minimum opening, so the air flow velocity when the intake valve opens is slow, and once it adheres to the intake pipe wall. The atomization rate of the fuel thus produced deteriorates, making it difficult to obtain a good air-fuel mixture. On the other hand, when fuel injection is started after the intake valve is opened, the amount of fuel adhering to the intake pipe wall is reduced because the fuel is injected toward the flowing intake air.

It is also known that atomization of fuel is promoted.

Furthermore, since the engine rotation during idling is very unstable and the amount of fuel supplied is small, even slight fluctuations in the amount of fuel supplied affect the engine rotation. In order to ensure the stability of engine rotation during idling, it is necessary to reduce the delay time from detection of the engine load state to combustion so that the optimum amount of fuel can be supplied to the engine. That is, it is desirable to match the time point at which the engine load is detected to the intake stroke period during which intake air is being drawn into the cylinder.

(Object of the invention) The present invention was made in view of the above problems, and
It is an object of the present invention to provide a fuel injection control method for an internal combustion engine, which optimizes the detection timing of the load state during idling and the fuel injection timing, and stabilizes the engine rotation.

(Structure of the Invention) In order to achieve the above object, according to the present invention, the load condition of the internal combustion engine is detected in response to an external interrupt signal, a fuel amount is calculated according to the detected load condition, and the fuel amount is calculated according to the detected load condition. In a fuel injection control method in which the injection supply of the calculated fuel quantity is started at the same time as the injection is completed, it is determined whether or not the engine is in an idling operating state, and when the engine is in an idling operating state, a predetermined crank angle after opening the intake valve is determined. 2. Start the computation in response to the external interrupt signal at the position, and start the computation in response to the external interrupt signal at a predetermined crank angle position before the intake valve opens when the engine is in an operating state other than the idle operating state. A method of controlling fuel injection for an internal combustion engine is provided.

(Embodiments of the invention) Examples of the invention will be described below based on the drawings. 1st
The figure shows the overall configuration of an electronic control device that implements the method of this invention. a first CPU 1 in an electronic control unit (ECU) that controls fuel supply to a four-cylinder internal combustion engine;
A second CPIJ2 is provided which controls the ignition timing of the air-fuel mixture formed by the supplied fuel. 1st C
The PUI is a read-only memory (hereinafter referred to as FROMJ) that stores various calculation programs executed by the first CPUI and various tables used to calculate the fuel injection amount, in other words, the opening time of the fuel injection valve 8. A random access memory 1 (hereinafter referred to as "RAM") 4 for temporarily storing calculation results, etc. is provided.

The input side of the first CPUI has an internal combustion engine intake pipe (
(not shown) A Pe transducer 5 detects the value of internal counter pressure, converts it into a digital value, and outputs it. It is connected to another transducer 6 that detects operating parameter values, converts them into digital values, and outputs them. Further, a counter circuit 7 that counts the opening time of the fuel injection valve based on fuel injection time data described later is connected to the output side of the first CPUI, and the output line of this counter circuit 7 is connected to the fuel injection valve 8. It is connected. Also the EGR valve.

Drive signal lines for solenoid valves and the like for idle control are connected to actuators 9 for these valves. Note that the fuel injection valve 8 is arranged for each cylinder of the internal combustion engine, and accordingly, the counter circuit 7 is also provided with the same number of counters as the number of cylinders.

On the other hand, the second CPU 2 includes a ROM II having the same functions as the first CPU 1.

and a RAM 12. A waveform shaping circuit 13 is connected to the input side of the second CPU 2, and a sensor for detecting the rotational position of the engine crankshaft is connected to the input side of the waveform shaping circuit 13. A cylinder discrimination (CYL) sensor 4 outputs a one-pulse signal T0□ for cylinder discrimination, and the reference crank is detected at a predetermined crank angle position of each cylinder's BTDC (before top dead center) every 180' rotation of the engine crankshaft. Angle signal T. a top dead center (TDC) sensor 5 that outputs 4;
and a crank angle sensor 6 which outputs a signal T24 of one pulse every time the crankshaft rotates by 30 degrees. Further, to the output side of the second C, PU 2, a flip-flop circuit 19 is connected in sequence via a turn-on counter 7 and a turn-off counter 8 that are connected in parallel, and an ignition circuit 21 and a distributor 22 are sequentially connected to the subsequent stage. Spark plugs 23a to 23d arranged for each cylinder are connected to the spark plugs 23a to 23d. The above-mentioned ignition port passage 21 has a high pressure generating unit (not shown).
A well-known ignition coil consisting of a primary coil and a secondary coil is provided. Further, the turn-on counter 7 and the turn-off counter 8 both use down counters, and as described later, the turn-on counter 17 is set with energization start timing data calculated by the second CPU 2. The starting crank angle position range (hereinafter simply referred to as the "energization stage")
), the clock pulse is subtracted from the stage starting point to determine the timing of energizing the primary coil of one ignition circuit 21. On the other hand, the turn-off counter 18 is set with the ignition timing data calculated by the second C'PU 2 in the same manner as described above, and subtracts and counts this from the stage start point using clock pulses at a predetermined ignition stage to be described later. It determines when to cut off the current to the coil and generates high voltage for ignition in the secondary coil.

Further, the following signal lines are connected between the first CPU I and the second CPU 2.

First, a signal line 25 for the cylinder discrimination (CYL) signal T, □ is connected between the output side of the waveform shaping circuit 13 and the hexagonal side of the first CPUI. Further, the signal line 26 that supplies the trigger signal q or q' for starting calculation to the first CPU is connected to the second CPU.
A communication line 27° 28 for data transfer is connected from U2 to the first CPU 1 (71), and a data transfer communication line 27° 28 is connected between both CPUs 2. The communication line 28 is connected from the first CPU The communication line 27 is used to transmit data such as engine parameters and transmission command signals, and the communication line 27 is used to send a confirmation signal τ, etc. for the above transmission command from the second CPU 2 to the first CPU. The CPUs 2 exchange necessary operating parameter detection data with each other via the communication lines 27 and 28. Reference numeral 29 is a Me counter, and the Me counter 29 includes a memory starting from the second CPU 2. Trigger signal lead line 3
0 is connected, and its output side is connected to the first CPUI.

The Me counter 29 indicates that the second CPU 2 is, for example, BTDC9.
A start trigger signal generated when a crank angle position of 0' is detected stores the counted value in a register (not shown), resets the counted value to zero, and starts counting clock pulses of a constant frequency again. . Therefore, the count value stored in the register of the Me counter 29 represents the number of clock pulses between the current and previous occurrences of the start trigger signal, ie, the time interval between occurrences of the start trigger signal.

This count value is read by the first CPUI and used to calculate a parameter Me that is proportional to the reciprocal of the engine speed Ne, and this parameter Me is used as information representing the engine speed when calculating the opening time of the fuel injection valve. is used as one of the parameters.

Next, the operation will be explained with reference to FIGS. 2 to 5.

First, ignition timing control by the second CPU 2 will be described.

The second CPU 2 receives CYL from each sensor 14 to 16.
Signal T0□, TDC signal T. The crank angle signal T24 is waveform-shaped by the waveform shaping circuit 13 and input (
Figures 2(a)-(C)). Among these, CYL signal T. , is also input to the first CPU via the signal line 25 as a signal for determining the order of fuel injection to each cylinder. In addition, the second
The stage in the figure and FIG.
The crank angle from each rise of T4 to the rise of the next crank angle signal T24 is divided into six regions at one interval, and each region is called a stage and numbered from 0 to 5. The second CPU 2 runs a crank interrupt processing program (FIG. 3(b)) which is executed each time the crank angle signal T24 is generated as an ignition timing control program, and a θIG which is executed after the end of the crank interrupt processing program. -DUTY calculation processing program (Figure 3 (C)
)) and execute the two processing programs θIG -DU
When the crank angle signal T24 is input during execution of the TY calculation process, the crank interrupt process is executed with priority.

First, in the crank interrupt processing, a reference crank angle position is determined based on the detection of the TDC signal, a trigger signal is generated to the Me counter 29 according to the procedure shown in FIG. ．． occurrence of q′,
Turn-on counter 1 based on crank angle signal T24
7 (stage 2 in the example of FIG. 3) and a predetermined stage (stage 4 in the example of FIG. 3) to start the turn-off counter 18.
), detects the generation time interval MESi of the crank angle signal T24, and executes controls such as starting the turn-on counter 17 and the turn-off counter 18.

On the other hand, in the θIG-DUTY calculation process, the advance angle control value θI
Calculation of each data such as G, energization control value DUTY (coil energization time ratio % to TDC signal generation time interval), etc. is executed.

To explain in more detail the calculation processing of each of the above data, the advance angle control value θIG is calculated based on the engine rotation speed Ne, the intake pipe absolute pressure PB
A, the engine coolant temperature Tw, etc. are calculated according to the following equation (1).

θIG=θMAp 10 IGCR...(1) Here, θ
MAI) indicates the basic advance angle value, and the engine speed Ne and
The intake pipe absolute pressure PBA is read out from the map stored in ROMII.

θIGCR is a correction variable value for the basic advance angle value, and is read out from the table stored in the ROM II according to the engine coolant temperature Tw, intake air temperature TA, atmospheric pressure P^, etc.

The engine speed Ne used to calculate the oMAp value is determined by a Me counter (not shown) built in the second CPU 2.
The value Me is given from each stage 0 to 1 of the crank angle signal T24 shown in FIG.
Addition value Me (=ME,, +MEs+MEsz+MEG3+
ME64+MEs5) is used.

Further, the energization control value DUTY is a function of the engine rotation speed Ne, and is read out from the table stored in the ROMII as described above, and is given by correcting this read value with the battery voltage.

Here, ignition is performed in the range from BTDCO to 60'', in other words, it is performed in either stage 4 or 5. Specifically, the data input to the turn-off counter 18 is from the rise of stage 4, When the turn-off counter 18 starts counting and the count reaches the value O, 2
Power to the next coil is cut off. Assuming that the input value to the turn-off counter 18 is TIG, the TIG is an angle-time conversion value, and the value is obtained from the advance angle control value OIG and the Me value obtained as described above.

In addition, the advance angle control value 0 engineering G is also used for the 1 energization start time TDUT.
, is a value obtained by converting the angle determined by the energization control value DUTY and the Me value, and thereby any position between the stages can be set.

When the stage start point at which energization should start for one ignition coil is detected, the turn-on counter 17 starts counting, and when the value corresponding to the TDtJT value is counted down and the count reaches the value 0, that is, the set energization is completed. When the start time is reached, the flip-flop circuit 19 is set, and the primary coil of the ignition circuit 21 starts to be energized.

As described above, the flip-flop circuit 19 is reset from the start of stage 4 to the ignition timing TIG.

The flip-flop circuit 19 is reset to the ignition circuit 2.
Outputs the energization off signal to 1, and outputs the energization off signal to 2 at the timing of energization off.
Next, a socket voltage for ignition is generated in the coil, and the plug 22 is ignited at a specified advance angle position.

Next, referring to FIG. 4, the calculation start trigger signals q, q executed in the crank interrupt processing on the second CPUZ side
The generation procedure of ' and the procedure of the FI calculation process executed on the first CPUI side in response to the calculation start trigger signal q+'T' will be explained with reference to FIG.

In Fig. 4, the reference crank angle position (
At the same time, the first stage #O of the six crank angle positions (stages) defined between each TDC position is detected. Then, each stage following stage #0 is detected based on each crank angle signal T24 input thereafter, and in the process, the determination operations of step 41 and step 46 are performed.

First, in step 41, the currently detected stage ST is the 3rd stage ST.
It is determined whether or not it is in the stage (ST=3). If the determination result is negative (NO), steps 42 to 45 are skipped and the process proceeds to step 46, and if affirmative (Yes), steps 42 to 45 are executed and the process proceeds to step 46. That is, when the third stage is detected, as described above, a start trigger signal is output to the Me counter 29 via the signal line 30 (step 42), and the engine coolant temperature inspection value Tw is determined as the discrimination value TWFI7 (for example, 78°C). It is determined whether or not it exceeds (step 43). If the determination result is negative (No), a variable INJS representing the stage at which a trigger signal for starting calculation should be generated, that is, the stage at which the CPU 1 should start calculating the valve opening time of the fuel injection valve.
The value 3 is set for T (step 44), and if the determination result is affirmative (Yes), it is determined whether the engine is in an idling operating state (step 45). For example, this determination is made when the absolute pressure in the intake pipe is a predetermined absolute pressure value (450 mmHg).
This is done by determining whether or not the following is true. If the determination result in step 45 is negative (No), the process goes to step 44, and if it is affirmative (Yes), the variable INJST is set to the value 0 (step 46), and the process proceeds to step 47 together.

Next, in step 47, it is determined whether or not the detected current stage ST is equal to the variable value INJST. If it is not equal to 1, the determination result is negative (NO) and the program is terminated. If the determination result is affirmative (Yes), a trigger signal q or q' for starting calculation is generated and supplied to the first CPUI via the signal line 26 (step 48).

That is, as shown in FIGS. 2 and 3, INJST=0
If so, the trigger signal q for starting calculation is sent at stage #O.
', and stage #3 if INJST=3
Then, the trigger signal q for starting calculation is output to the first CPUI via the signal line 26, and this program is ended.

On the other hand, in the first CPUI, the FI arithmetic processing program is activated in response to the arithmetic trigger signal q or q'. That is, as shown in FIG. 3, the FI calculation process is executed at stage #0 in an idling operating state, and is executed at stage #3 in an operating state other than idling. In this FI calculation process, the flowchart shown in FIG.
) and the absolute pressure in the intake pipe from the P8 transducer 5 are read (step 52). When a reading command is issued to the PB transducer 5, the absolute pressure in the intake pipe at that time is detected. Then, proceeding to step 53, the RAM
4 is stored in the throttle valve opening signal 87H1, and data such as the OJ degree detection value in the exhaust gas is read, and from these data and the Me value and PB value read in the steps 51 and 52, the fuel injection valve, which will be described later, is determined. Valve opening time TOLI
Perform the calculation of T. Then, at the same time as the calculation of the T o and J T values is completed, the data of the calculated valve opening time TOIJT is set in the counter of a predetermined cylinder in the counter circuit 7, and the counter is activated (step 54).
.

As a result, the drive signal S corresponding to the 2 valve opening time T 0LIT
' (when idling) or S (when operating in a state other than idling)
is supplied to the fuel injection valve 8, and the fuel injection start timing is controlled to be switched between an idling operating state and an operating state other than idling.

Here, the fuel injection start timing during idling is a predetermined crank angle position after the TDC position at the start of the intake stroke (for example, a predetermined crank angle position at stage #0), which is after the intake valve (not shown) has opened. corresponds to the time. Therefore, even if the airflow speed in the intake pipe (not shown) is slow, the injected fuel is taken into the cylinder by the airflow, improving the fuel atomization efficiency and maintaining a good mixture of fuel and air. can be made into something.

In addition, as soon as the trigger signal q' is input, the intake pipe absolute pressure PB is detected and this is reflected in the calculation of the valve opening time TOUT, so the delay time from detection of the intake pipe absolute pressure PR to combustion is shortened. This makes it possible to stabilize engine rotation.

Note that even during idle, the star 1 to trigger signals to the Me counter 29 are output at stage 3 (BTDC90'), but the Me value read in step 48 during idle is the latest one updated by the start trigger signal. It is.

On the other hand, the fuel injection start timing in operating states other than idling is a predetermined crank angle position before the TDC position at the start of the intake stroke (for example, a predetermined crank angle position in stage #3), which is before the intake valve opens. It corresponds to the point in time and is the same as before.

The above-described valve opening time T o'r of the fuel injection valve 8 is calculated by the following equation.

Tout=TiXK1+K.

Here, Ti indicates the basic valve opening time of the fuel injection valve 8, and this basic valve opening time Ti is, for example, the intake pipe absolute pressure POA,
It is read out from the ROM 3 based on the engine rotation speed Ne. NIK and NI2 are correction coefficients and correction variables respectively calculated according to the engine parameter signals from the various sensors mentioned above, and depending on the engine operating condition, start characteristics, exhaust gas characteristics, fuel consumption characteristics, engine acceleration. Calculation is performed based on a predetermined calculation formula so that various characteristics such as characteristics are optimized.

In the above-mentioned embodiment, a so-called dual CPU type electronic control unit is used to control switching of fuel injection timing between idling and non-idling operating states. 1 CPU
When using INJST=O or INJST=3
In response to the stage determination (step 47), it is preferable to read the intake pipe absolute pressure Pa and Me value, and to calculate and output the valve opening time TOυT.

Further, the determination as to whether or not the engine is in an idling operating state (step 45) may be made based on the throttle valve opening or the engine rotational speed.

(Effects of the Invention) As detailed above, according to the fuel injection control method for an internal combustion engine of the present invention, the fuel injection timing during idling is set after the intake valve is opened, so that the injected fuel flows into the intake air flow. The fuel is then sucked into the cylinder, improving atomization efficiency and making the air-fuel mixture in a good condition. Further, since the intake pipe absolute pressure is detected at the time of starting the fuel supply amount calculation, the latest value is reflected in the calculation, and the optimum fuel supply amount can be accurately calculated.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram showing an example of an electronic control device implementing the fuel injection control method according to the present invention, Fig. 2 is a timing chart showing the generation timing of the TDC signal, crank angle signal, etc., and Fig. 3 is an idle Trigger signal ql' for starting calculation in operating state and in other operating states? 4 is a flowchart showing the procedure for issuing the trigger signal q'+9 for starting the calculation, and FIG. 5 is the trigger signal q'yq for starting the calculation.
2 is a flowchart showing a calculation procedure for the valve opening time T 0LIT of the fuel injection valve in response to the above. 1...First CPU, 2...Second CPU, 5...
・Intake pipe absolute pressure transducer, 8...Fuel injection valve, 16...Crank angle sensor, 26...Trigger signal q+ q' sending signal line for starting calculation, 29...M
e counter.

Claims (1)

[Claims] 1. In a fuel injection control method, the load state of an internal combustion engine is detected in response to an external interrupt signal, the amount of fuel is calculated according to the detected load state, and the injection supply of the calculated amount of fuel is started simultaneously with the completion of the calculation. , determines whether or not the engine is in an idling operating state, and when the engine is in an idling operating state, starts calculation in response to the external interrupt signal at a predetermined crank angle position after opening the intake valve; 1. A fuel injection control method for an internal combustion engine, characterized in that when the operating state is 1, an operation in response to the external interrupt signal is started at a predetermined crank angle position before the intake valve is opened.