JP3211542B2 - 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 system for controlling the amount of fuel supplied to a combustion chamber of an internal combustion engine using an ignition plug for igniting an air-fuel mixture. The present invention relates to a control device.

[0002]

2. Description of the Related Art Conventionally, in a general internal combustion engine, fuel is injected from a fuel injection valve into air (intake air) flowing through an intake passage to generate an air-fuel mixture. Further, the air-fuel mixture taken into the combustion chamber via the intake passage is ignited by a spark plug. The secondary voltage of the secondary coil of the ignition coil is supplied to the ignition plug. When the secondary voltage reaches the required voltage, discharge occurs between the electrodes of the spark plug. The mixture is ignited by this discharge and burns in the combustion chamber. The gas generated by the combustion is purified by the catalyst in the exhaust passage and then discharged to the outside of the engine.

In such an internal combustion engine, when controlling fuel injection by a fuel injection valve, a basic injection amount is calculated based on an intake air amount to the engine and an engine rotation speed (or an intake pipe pressure), and the value is corrected. Thus, the final injection amount is determined. One of such corrections is air-fuel ratio feedback control using an air-fuel ratio correction coefficient. That is, the catalyst provided in the exhaust passage exhibits high purification performance when the air-fuel ratio becomes the stoichiometric air-fuel ratio. The air-fuel ratio is the weight ratio of air to fuel in the air-fuel mixture, and the stoichiometric air-fuel ratio is the air-fuel ratio of the air-fuel mixture including the amount of oxygen necessary to completely oxidize the fuel.

[0004] In the air-fuel ratio feedback control, the concentration of residual oxygen in the exhaust gas is detected by an oxygen sensor upstream of the catalyst in the exhaust passage in order to bring the air-fuel ratio close to the stoichiometric air-fuel ratio. An air-fuel ratio correction coefficient is calculated based on the detection signal, and the correction coefficient is multiplied to correct the basic injection amount. By performing the fuel injection according to the injection amount obtained by the correction, the air-fuel ratio is converged to the vicinity of the stoichiometric air-fuel ratio.

On the other hand, in the above internal combustion engine, there is a correlation between the required voltage of the ignition plug and the secondary voltage of the ignition coil, and the air-fuel ratio of the air-fuel mixture near the electrode of the ignition plug. Specifically, as the air-fuel ratio becomes larger than the stoichiometric air-fuel ratio, that is, as the air-fuel mixture becomes leaner, the absolute value of the required voltage tends to increase, and the absolute value of the secondary voltage tends to increase accordingly.

[0006]

Incidentally, the air-fuel ratio of the air-fuel mixture is not uniform at every point in the combustion chamber, but actually varies depending on the point. For example, during transients such as rapid acceleration of the engine, the air-fuel mixture in the vicinity of the electrode of the ignition plug may be partially leaner than other portions. In this case, the absolute values of the required voltage and the secondary voltage both increase according to the air-fuel ratio of the air-fuel mixture near the electrodes. If the absolute value of the required voltage becomes higher than the maximum value of the absolute value of the secondary voltage that can be generated by the ignition coil, a phenomenon that no discharge occurs between the electrodes (misfire) occurs.

However, in the above-described conventional fuel injection control technique, the air-fuel ratio correction coefficient is simply calculated based on the detection signal of the oxygen sensor, regardless of the air-fuel ratio bias in the combustion chamber.
Only the basic injection amount is corrected with this correction coefficient. For this reason, it is difficult to suppress the occurrence of the misfire.

[0008] Incidentally, as a related technology of misfire, for example,
Japanese Patent Application Laid-Open No. 61-155662 discloses an "ignition failure detection device for an ignition plug". However, this technology only clarifies the relationship between the secondary voltage and misfire, and uses that relationship to detect poor ignition, but does not go on to suppress misfire from the behavior of the secondary voltage. .

The present invention has been made in view of the above-described circumstances, and has as its object to estimate the air-fuel ratio of an air-fuel mixture in the vicinity of a spark plug from a secondary voltage of an ignition coil, and utilize the estimation result to prevent misfire. An object of the present invention is to provide a fuel injection control device for an internal combustion engine that can suppress the occurrence.

[0010]

In order to achieve the above object, the present invention, as shown in FIG. 1, is provided in an intake passage M3 communicating with a combustion chamber M2 of an internal combustion engine M1.
A fuel injection valve M4 that injects fuel into the air flowing through to generate an air-fuel mixture, a primary coil and a secondary coil, and current supply to the primary coil is cut off.
An ignition coil M5 that generates a secondary voltage in the secondary coil; and an ignition coil M5 that is connected to the ignition coil M5 and discharges between the electrodes by the secondary voltage from the secondary coil to form a mixture in the combustion chamber M2. A spark plug M6 for igniting,
An operating state detecting means M7 for detecting an operating state of the internal combustion engine M1, an injection amount calculating means M8 for calculating an injection amount from a fuel injection valve M4 according to an operating state by the operating state detecting means M7, An injection control means M9 for driving and controlling the fuel injection valve M4 so as to obtain an injection amount by the calculation means M8, a voltage detection means M10 for detecting a secondary voltage of an ignition coil M5 when the ignition plug M6 is discharged, A storage means M11 in which the absolute value of the secondary voltage of the ignition coil M5 when the air-fuel ratio, which is the ratio of air to fuel in the air-fuel mixture, becomes a predetermined value is stored in advance as a threshold value; ratio is larger than the predetermined value, the absolute value of the secondary voltage by the voltage detecting means M10 is greater than the threshold value of the storage means M11
The fuel injection of the internal combustion engine is provided with an injection amount correction means M12 for increasing and correcting the injection amount of the injection amount calculation means M8 under the condition
A fuel injection control device, wherein the injection amount correction means includes:
When the correction execution condition is first satisfied after the engine is started
Is the initial increase value to bring the air-fuel ratio closer to the stoichiometric air-fuel ratio.
Thus, the injection amount of the injection amount calculating means is increased and corrected.
On the other hand, when the execution condition is satisfied for the second and subsequent times, the threshold
Increase in accordance with the deviation between the maximum value of the secondary voltage and the maximum value of the secondary voltage
The injection amount of the injection amount calculation means is increased and corrected using the value.
The gist is that it is something .

[0011]

[0012]

According to the present invention, the operating state of the internal combustion engine M1 is detected by the operating state detecting means M7. The injection amount from the fuel injection valve M4 according to this operation state is calculated by the injection amount calculation means M8. Then, the fuel injection valve M4 is driven and controlled by the injection control means M9 so that the calculated injection amount is obtained. According to this control, the fuel injection valve M4
Fuel is injected from the intake passage M3
Is mixed with the air flowing through the combustion chamber M.
It is led to 2.

On the other hand, in the ignition coil M5, the supply of current to the primary coil is cut off, so that a secondary voltage is generated in the secondary coil. When the secondary voltage reaches a voltage (required voltage) required for discharge at the spark plug M6, discharge occurs between the electrodes, and the mixture in the combustion chamber M2 is ignited to perform combustion.

Incidentally, these required voltages and secondary voltages are affected by the air-fuel ratio which is the ratio of air to fuel in the air-fuel mixture. That is, when the air-fuel ratio becomes larger than the predetermined value, the absolute values of the required voltage and the secondary voltage tend to increase. Therefore, if the absolute value of the secondary voltage is grasped, the degree of the air-fuel ratio can be estimated.

On the other hand, in the present invention, the spark plug M6
The secondary voltage of the ignition coil M5 at the time of discharging is detected by the voltage detecting means M10. The injection amount correction means M12 determines whether or not the absolute value of the secondary voltage by the voltage detection means M10 is larger than the threshold value of the storage means M11. This threshold value is the absolute value of the secondary voltage of the ignition coil M5 when the air-fuel ratio in the air-fuel mixture reaches a predetermined value. Therefore, whether the air-fuel ratio is larger than a predetermined value is determined by comparing the absolute value of the secondary voltage with the threshold value.

On the condition that it is determined that the absolute value of the secondary voltage is larger than the threshold value (the air-fuel ratio is larger than a predetermined value and the air-fuel mixture is lean), the injection amount calculating means M
The injection amount of No. 8 is increased by the injection amount correcting means M12. Therefore, even if the absolute values of the required voltage and the secondary voltage increase due to the dilution of the mixture near the ignition plug M6,
The air-fuel ratio of the air-fuel mixture is made appropriate by increasing the amount of fuel. This optimization prevents the required voltage from becoming higher than the maximum possible value of the secondary voltage.

Here, suppose that the correction amount is a fixed value and the characteristics of the secondary voltage in the internal combustion engine M1 where misfiring is most likely to occur are taken into account in consideration of variations in the characteristics of the secondary voltage for each internal combustion engine M1. It is assumed that the correction amount is determined. Then, in the other internal combustion engine M1, the fuel is excessively increased and corrected. For this reason , when the injection amount is increased by the injection amount correcting means M12, the correction amount for increasing the injection amount is changed according to the deviation between the threshold value and the maximum absolute value of the secondary voltage. Therefore, even if the characteristics of the secondary voltage vary among the internal combustion engines M1 as described above, the correction amount is changed according to the characteristics, so that the fuel increase correction can be performed for each internal combustion engine M1 without excess or deficiency. Done. In addition, this increase
When performing the amount correction, the condition for executing the
When first established after starting, the air-fuel ratio is set to the stoichiometric air-fuel ratio.
The injection amount is increased with the initial increase value to approach
On the other hand, when the execution condition is satisfied for the second and subsequent times,
The difference between the threshold value and the maximum absolute value of the secondary voltage is
The injection amount is increased and corrected with the increased amount.

[0018]

FIG. 2 shows an embodiment of the present invention.
This will be described with reference to FIG.

FIG. 2 is a schematic configuration diagram of a gasoline engine (hereinafter simply referred to as an engine) 1 as an internal combustion engine mounted on a vehicle. Cylinder block 1a of engine 1
Has multiple cylinders (cylinders, cylinders,
(Only one is shown in the figure) 2. A piston 3 is accommodated in each cylinder 2 so as to be able to reciprocate up and down. The piston 3 is connected to the crankshaft 5 by a connecting rod 4.

A combustion chamber 6 is formed above the piston 3, and an intake passage 7 and an exhaust passage 8 communicate with each other.
A communication portion between the combustion chamber 6 and the intake passage 7 is an intake port 9, and the intake port 9 is opened and closed by an intake valve 11 movably mounted on the cylinder head 1b. The communicating portion between the combustion chamber 6 and the exhaust passage 8 is an exhaust port 10, which is opened and closed by an exhaust valve 12 mounted on the cylinder head 1b so as to be vertically movable.

The intake passage 7 has a combustion chamber 6 from the upstream side.
Toward the air cleaner 13, the throttle body 1
4, a surge tank 15 and an intake manifold 16 are provided, through which air outside the engine is supplied to the combustion chamber 6.
It is taken in. A throttle valve 17 is supported in the throttle body 14 by a shaft 18 so as to be integrally rotatable. The shaft 18 is connected to an accelerator pedal (not shown) by a cable or the like. When the driver depresses the accelerator pedal, the depressing operation is transmitted to the shaft 18 via a cable or the like, and the throttle valve 17 rotates integrally with the shaft 18. The rotation of the throttle valve 17 opens and closes the intake passage 7, and the amount of air (intake air) flowing through the intake passage 7 is adjusted. The surge tank 15
It is a tank for smoothing the pulsation of the intake air and preventing intake interference of each cylinder.

An electromagnetic fuel injection valve 19 for supplying fuel to each cylinder is mounted on the intake manifold 16. The fuel injection valve 19 includes a needle valve, a solenoid coil, and the like. When the solenoid coil is energized, the needle valve moves to open the injection port.
High-pressure fuel is injected with the opening of the injection port. A mixture of fuel and intake air injected from each fuel injection valve 19 is introduced into the combustion chamber 6 through the intake port 9 when the intake valve 11 is opened.

An ignition device 20 of a semiconductor ignition system is provided for igniting the air-fuel mixture introduced into the combustion chamber 6.
The ignition device 20 includes an igniter 21, an ignition coil 23, a distributor 26, and a spark plug 28 for each cylinder. Further, the ignition device 20 includes a high tension cord 32 for connecting between the distributor 26 and each ignition plug 28.

As shown in FIG. 3, the spark plug 28 has a center electrode 29 for generating a spark discharge in the combustion chamber 6 and a ground electrode 31. Both electrodes 29 and 31 are arranged at a predetermined interval. As shown in FIG. 2, the ignition coil 23 is a kind of transformer for generating a high voltage required for ignition by the spark plug 28, and is formed by stacking a secondary coil and a primary coil around an iron core. It is configured by winding. The transistor of the igniter 21 operates based on an external ignition signal, and permits or cuts off the current to the primary coil of the ignition coil 23 (intermits the primary current).

The distributor 26 distributes the high voltage generated in the secondary coil of the ignition coil 23 to the ignition plug 28 of each cylinder in a certain order, and supplies the high voltage to the cylinder head 1b or a cam head (not shown). It is assembled. Distributor 26
Is provided with a shaft 27 that is driven to rotate with the operation of the engine 1. That is, the shaft 27 is gear-coupled or coupled with a camshaft (not shown), and rotates at half the rotational speed of the crankshaft 5.

The electrical configuration of the ignition device 20 will be described with reference to FIG. 4. An ignition switch 34, the primary coil 24 of the ignition coil 23, and the igniter 21 are connected in series to a battery 33 mounted on the vehicle. The distributor 26 is connected to a connection point a between the ignition switch 34 and the primary coil 24 via the secondary coil 25 of the ignition coil 23. The ignition plug 28 of each cylinder is connected to the distributor 26.

When an ignition signal from the outside (an electronic control unit to be described later) is input to the igniter 21 with the ignition switch 34 turned on, the igniter 21 drives the transistor 22 based on the ignition signal. , The power supply to the primary coil 24 is allowed or cut off. When energization of the primary coil 24 is cut off, a back electromotive force corresponding to the primary current at that time is generated in the primary coil 24. Induced by this back electromotive force, the secondary coil 2
5, a high voltage (generally 10 to 30 kV) secondary voltage Vr is generated. The secondary voltage Vr is distributed by the distributor 26 to the ignition plug 28 for each cylinder, and is applied between the electrodes 29 and 31 of the plug 28. Then, a current flows between the two electrodes 29 and 31 (discharge occurs), and a spark is generated.

That is, as shown in FIG.
When the primary current is cut off at 1, the absolute value of the secondary voltage Vr increases (the secondary voltage Vr decreases). When the absolute value of the secondary voltage Vr reaches the absolute value of the voltage (required voltage) required for discharging the spark plug 28 at the timing t2 during the rise, a spark occurs between the electrodes 29 and 31.

The generation of the spark activates the air-fuel mixture between the electrodes 29 and 31 to cause a chemical reaction. Flame nuclei are generated by the reaction heat generated by this reaction. This nucleus activates the surrounding air-fuel mixture with its own heat, and eventually becomes a nucleus of a flame that spreads its combustion to the surroundings.

There is a close relationship between the secondary voltage Vr and the required voltage of the spark plug 28, and the air-fuel ratio (air-fuel ratio) of the air-fuel mixture near the two electrodes 29 and 31.
As the air-fuel ratio increases (the mixture becomes thinner), the absolute value of the required voltage increases, and the absolute value of the secondary voltage Vr tends to increase accordingly.

As shown in FIG. 2, the air-fuel mixture introduced into the combustion chamber 6 is burned by the ignition of the spark plug 28 as described above. This combustion activates the piston 3,
The reciprocating motion is converted into a rotational motion by the connecting rod 4, and the crankshaft 5 is driven to rotate.
Gas (exhaust gas) generated by combustion in the combustion chamber 6 is:
When the exhaust valve 12 is opened, it is led out of the exhaust port 10 to the exhaust passage 8.

The exhaust passage 8 is provided with an exhaust manifold 35 and a catalytic converter 36 in order from the combustion chamber 6 to the downstream side, through which exhaust gas is discharged to the outside. The catalytic converter 36 is a device that purifies hydrocarbon (HC), carbon monoxide (CO), and nitrogen oxide (NOx) in exhaust gas by the action of a catalyst.

Each part of the engine 1 has an air flow meter 3 as an operating state detecting means for detecting its operating state.
7, an intake air temperature sensor 38, a throttle sensor 39, a water temperature sensor 40, an oxygen sensor 41, a rotation speed sensor 42, a reference position sensor 43, and the like.

The air flow meter 37 is an air flow meter for measuring the amount of air taken in by the engine 1. In this embodiment, a measuring plate (vane) is pushed and opened by a pressure difference generated when the intake air passes. Type is used. The intake air temperature sensor 38 is mounted in the air flow meter 37 and detects a change in the temperature of the intake air flowing through the intake passage 7 based on a change in the resistance value of a built-in thermistor.

The throttle sensor 39 is attached to the throttle body 14, and outputs an idle signal when the throttle valve 17 is fully closed. When the throttle valve 17 is slightly open, the opening (throttle opening) is detected. I do. The water temperature sensor 40 is attached to a water outlet housing or the like, and detects the temperature of the cooling water of the engine 1 (cooling water temperature). The oxygen sensor 41 is connected to the exhaust manifold 3
5 for detecting the oxygen concentration in the exhaust gas.

The reference position sensor 43 is for detecting a crank angle reference position (for example, compression top dead center) of a specific cylinder, and is built in the distributor 26.
The reference position sensor 43 includes a timing rotor that rotates integrally with the shaft 27, and a pickup coil disposed outside the timing rotor. The sensor 43 outputs a pulse-like reference position signal every time one projection on the timing rotor passes in front of the pickup coil with the rotation of the shaft 27.

The rotation speed sensor 42 is connected to the crankshaft 5
This is for detecting the rotation speed (engine rotation speed), and is built in the distributor 26 as in the case of the reference position sensor 43. The rotation speed sensor 42 includes a timing rotor that rotates integrally with the shaft 27, and a pickup coil disposed outside the timing rotor. A large number of projections are formed at equal angles on the outer periphery of the timing rotor. The sensor 42 outputs a pulse-shaped rotation speed signal every time the projection on the timing rotor passes in front of the pickup coil with the rotation of the shaft 27.

Further, in this embodiment, as shown in FIG.
A voltage attenuator 44 as voltage detection means is connected to a connection point b between the secondary coil 25 of the ignition coil 23 and the distributor 26. This voltage attenuator 4
Reference numeral 4 denotes a voltage output from the ignition coil 23 (a voltage obtained by combining the primary voltage and the secondary voltage), for example, 1/1.
000, and only the secondary voltage Vr is detected. The detected secondary voltage Vr is attenuated to a level that can be input to an electronic control device described later.

As shown in FIG. 2, the air flow meter 3
7. An electronic control unit (hereinafter referred to as ECU) for controlling the operation of the fuel injection valve 19 and the igniter 21 based on the detection signals of the various sensors 38 to 43 and the voltage attenuator 44.
45 are provided.

As shown in FIG. 6, the ECU 45 comprises a central processing unit (hereinafter referred to as CPU) 46 which constitutes injection amount calculating means, injection control means and injection amount correcting means, and a read-only memory (hereinafter referred to as ROM) as storage means. 47, random access memory (hereinafter referred to as RAM) 48, backup RAM 49, external input circuit 50, external output circuit 5
1 which are connected to each other by a bus 52. The ROM 47 stores a predetermined control program and initial data in advance. The CPU 46 executes various arithmetic processes according to the control program and the initial data. RA
M48 temporarily stores the calculation result by the CPU 46. The backup RAM 49 is backed up by the battery 33 to retain various data in the RAM 48 even after the power supply to the ECU 45 is stopped.

The intake air amount signal from the air flow meter 37, the intake air temperature signal from the intake air temperature sensor 38, the throttle opening signal and idle signal from the throttle sensor 39, the cooling water temperature signal from the water temperature sensor 40, the oxygen sensor 4
1, the rotation speed signal from the rotation speed sensor 42, the reference position signal from the reference position sensor 43, and the output voltage (secondary voltage Vr) of the voltage attenuator 44 are input to the external input circuit 50. . Based on these signals, the CPU 46 determines the intake air amount Q, intake air temperature THA, throttle opening TA, idle signal, cooling water temperature THW, oxygen concentration, engine speed NE, reference position, secondary voltage Vr of the ignition coil 23, and the like. Is detected.

On the other hand, the CPU 46 controls the igniter 21 via the external output circuit 51. That is, the engine 1
The optimal ignition timing according to the operating state of the engine 1 is stored in the ROM 47 in advance, and the CPU 46 detects the operating state of the engine 1 based on signals from the various sensors, and calculates the optimal ignition timing. Then, the CPU 46 controls the external output circuit 51.
An ignition signal is output to the igniter 21 through the, and the ignition timing of the ignition plug 28 is controlled.

The CPU 46 controls the operation of the fuel injection valve 19 via the external output circuit 51 as follows. The flowchart of FIG. 7 shows a routine for controlling the fuel injection amount among the processes executed by the CPU 46. The processing of this routine is performed by the engine 1
Switch 3 by the driver for starting
4 is started when the switch 4 is turned on, and thereafter is executed at predetermined timings. The processing of this routine is performed based on the flag F. The flag F is used to determine whether or not the fuel increase correction has been performed for the first time after the engine is started. The flag F is initially set to “0” when the engine is started, and is set to “0” when the fuel increase correction is performed for the first time. 1 ".

Here, the fuel injection amount is determined by the time during which the needle valve of the fuel injection valve 19 is open (injection time), that is, the time of energizing the solenoid coil. Therefore, in the routine of FIG. 7, the injection time TAU is calculated as the injection amount.

When the fuel injection control routine is started, C
The PU 46 first determines in step 101 that the voltage attenuator 4
The secondary voltage Vr of the ignition coil 23 which is the output voltage of No. 4 is detected. Subsequently, the CPU 46 determines in step 102
, It is determined whether or not the absolute value of the secondary voltage Vr is greater than a preset threshold value α. This threshold value α is the absolute value of the secondary voltage Vr of the ignition coil 23 when the air-fuel ratio of the air-fuel mixture reaches a predetermined value. As the predetermined value, for example, an air-fuel ratio (stoichiometric air-fuel ratio) of an air-fuel mixture that contains the amount of oxygen necessary to completely oxidize the fuel can be set.

The ratio of fuel in the air-fuel mixture is smaller than that in the case of the stoichiometric air-fuel ratio, and the air-fuel mixture is lean.
If the absolute value of the secondary voltage Vr is larger than the threshold value α, CP
U46 determines that the determination condition of step 102 is satisfied, and proceeds to step 103. In this step, the CPU 46 determines whether or not the flag F is “0”.

If the flag F is "0", the CPU 46 determines that the increase correction has not been performed yet after the engine is started, and in step 104, the increase value βi is added to the wall surface adhesion correction amount FMW calculated by another routine. Is added, and the addition result is set as a new wall surface adhesion correction amount FMW. The wall surface adhesion correction amount FMW is a correction amount for preventing the air-fuel ratio from being disturbed by the fuel wall surface adhesion. Also, the increase value βi
Is an initial value for increasing the fuel injection amount,
47 is stored in advance.

The CPU 46 changes the flag F from "0" to "1" at step 105, and proceeds to step 106 to calculate the injection time TAU of the fuel injector 19 according to the following equation. TAU = TP × f + FMW (1) In the above equation (1), TP is a basic injection time determined by a ratio between the intake air amount Q and the engine speed NE,
f is a correction coefficient. As the correction coefficient f, for example, there is a coefficient related to feedback control of intake air temperature, increase in warm-up, increase after start-up, increase in output, and air-fuel ratio.

The coefficient relating to the intake air temperature is for correcting a deviation of the air-fuel ratio caused by the difference in the density of the intake air due to the intake air temperature, and is obtained based on the intake air temperature THA. The coefficient related to the increase in warm-up is for improving the drivability in a cold state, and is obtained based on the cooling water temperature THW. The coefficient related to the increase after the start is to stabilize the engine speed NE immediately after the engine is started,
It is determined based on the cooling water temperature THW.

The coefficient relating to the increase in the output is used to correct the increase in the injection amount when the catalytic converter 36 is likely to overheat (at high load). With this increase, the engine 1
The operability under a high load is improved, and an increase in the catalyst temperature is suppressed. The coefficient related to the output increase is obtained based on the intake air amount Q, the engine speed NE, and the throttle opening TA.

The coefficient relating to the feedback control of the air-fuel ratio is for correcting the basic injection time so that the air-fuel ratio of the air-fuel mixture always converges to the stoichiometric air-fuel ratio. Therefore, the CPU 46 determines whether the air-fuel ratio is smaller than the stoichiometric air-fuel ratio (rich) or larger than the stoichiometric air-fuel ratio (lean) based on a signal from the oxygen sensor 41. , The basic injection time TP is lengthened.

Accordingly, the injection time TAU obtained by the processing in step 106 includes an increase (βi) for bringing the air-fuel ratio closer to the stoichiometric air-fuel ratio. In the present embodiment, the injection amount calculating means is constituted by the CPU 46 and the processing of the step 106.

Next, in step 107, the CPU 46 outputs a drive signal corresponding to the injection time TAU to the fuel injection valve 19 via the external output circuit 51. In accordance with this signal, the time for energizing the solenoid coil of the fuel injection valve 19 is controlled, the time during which the needle valve is open is adjusted, and a predetermined amount of fuel is injected from the injection valve 19. In this embodiment, the injection control means is constituted by the CPU 46 and the processing of the step 107.

The injection time TAU corrected as described above
When fuel injection is performed based on the above, the proportion of fuel in the air-fuel mixture increases. Accordingly, the air-fuel mixture near the electrodes 29 and 31 of the ignition plug 28 becomes rich, and the secondary voltage Vr
Becomes smaller. That is, when the increase correction is not performed, the secondary voltage Vr has a waveform shown by a broken line in FIG. On the other hand, in the present embodiment, the secondary voltage Vr has a waveform shown by a solid line in the same figure due to the increase correction, and the absolute value of the secondary voltage Vr during the discharge of the spark plug 28 as compared with the case without the increase correction. The value decreases.

Subsequently, the CPU 46 determines in step 108 that the peak value Vr of the absolute value of the secondary voltage Vr at that time.
Find peak. That is, when the absolute value of the secondary voltage Vr changes from increasing to decreasing (in FIG.
(when r changes from decreasing to increasing) the peak value Vrpe
Ask as ak.

Then, in step 109, the CPU 46 calculates a deviation ΔV between the absolute value of the peak value Vrpeak and the threshold value α. In step 110, the CPU 46 obtains an increase value βnew according to the deviation ΔV from a map (not shown). This map defines the increment value βnew for each deviation ΔV, and is stored in the ROM 47 in advance. When the increase value βnew is obtained, the CPU 46 uses the value βnew as a learning value in the RAM in preparation for the next fuel injection.
48, and this routine is temporarily ended.

If the absolute value of the secondary voltage Vr is larger than the threshold value α in the next and subsequent control cycles, despite the fuel increase correction as described above, the CPU 46 performs the processing in the following order. .

After executing the processing of step 101, the CPU 46 determines that the determination condition of step 102 is satisfied. Since the flag F is set to “1” in step 105 of the previous control cycle, the CPU 46 determines that the determination condition of step 103 is not satisfied, and proceeds to step 111. In this step 111, the CP
U46 is the increment value βnew stored in step 110.
Then, in step 112, the increase value βnew is added to the wall surface adhesion correction amount FMW calculated by another routine.
Is added, and the addition result is added to a new wall adhesion correction amount FM.
W. In this embodiment, the injection amount correcting means is constituted by the CPU 46 and each of the processes of steps 102, 104, and 112.

In step 106, the CPU 46 calculates the injection time TAU according to the above equation (1). The injection time TAU includes an increment (βnew) for bringing the air-fuel ratio closer to the stoichiometric air-fuel ratio. In step 107, the CPU 46 outputs a drive signal corresponding to the injection time TAU to the fuel injection valve 19 via the external output circuit 51. The valve opening time of the fuel injector 19 is adjusted according to this signal, and a predetermined amount of fuel is injected from the injector 19.

The injection time TAU corrected as described above
When the fuel injection is performed based on the above, the proportion of the fuel in the air-fuel mixture further increases. Accordingly, the mixture near the electrodes 29 and 31 of the ignition plug 28 becomes rich, and the absolute value of the secondary voltage Vr further decreases as shown in FIG.

Subsequently, the CPU 46 proceeds to steps 108-1.
10, the peak value Vrpeak of the secondary voltage Vr and the deviation Δ
V is obtained, and an increase value βnew corresponding to the deviation ΔV is obtained from the map. The CPU 46 stores the increased value βnew as a learning value in the RAM 48 in preparation for the next fuel injection, and terminates this routine once.

When the absolute value of the secondary voltage Vr becomes smaller than the threshold value α by the above-described fuel increase correction, the CPU 46 proceeds to step 101 in the next and subsequent control cycles.
After executing the processing of (1), it is determined that the determination condition of step 102 is not satisfied, and the routine goes to step 113. Then, in step 113, the CPU 46 uses the wall surface adhesion correction amount FMW calculated by another routine as it is as the wall surface adhesion correction amount FMW at that time. And C
The PU 46 executes the processing of steps 106 to 110 described above, and once ends the processing of this routine.

As described above, in this embodiment, the spark plug 28
Secondary voltage V of the ignition coil 23 during the discharge of
r is detected by the voltage attenuator 44. It is determined whether the absolute value is greater than threshold α. This threshold value α is the absolute value of the secondary voltage Vr of the ignition coil 23 when the air-fuel ratio in the air-fuel mixture reaches a predetermined value (theoretical air-fuel ratio). Based on the comparison with the value α, it is determined whether the air-fuel ratio is larger than a predetermined value.

When the absolute value of the secondary voltage Vr is larger than the threshold value α (the air-fuel ratio is larger than a predetermined value and the air-fuel mixture is lean), the injection amount (injection time TAU) is increased. You. Therefore, the required voltage and the secondary voltage Vr are reduced by the dilution of the air-fuel mixture near the electrodes 29 and 31 of the spark plug 28.
Even if the absolute values of the air-fuel ratio increase, the air-fuel ratio of the air-fuel mixture can be adjusted to an appropriate value by increasing the amount of fuel. By this optimization, the required voltage is prevented from becoming higher than the maximum value of the secondary voltage Vr, and the occurrence of misfire can be suppressed.

Also, suppose that the increase value is a fixed value, and considering the variation in the characteristics of the secondary voltage Vr for each engine 1, the characteristic of the secondary voltage Vr in the engine 1 where misfiring is most likely to occur is taken as a reference. Assume that the increase value is determined. Then, in the other engines 1, the fuel is excessively increased. As a result, even if the occurrence of misfire can be suppressed, new problems such as an increase in exhaust gas and poor drivability arise. On the other hand, in the present embodiment, when increasing the injection amount, the increase value βnew is changed according to the deviation ΔV between the threshold value α and the peak value Vrpeak of the absolute value of the secondary voltage Vr. Therefore, even if the characteristics of the secondary voltage Vr vary from engine 1 to engine 1 as described above, the fuel increase correction can be performed without excess or deficiency by changing the increase value according to the characteristics. Then, occurrence of misfire can be prevented without increasing exhaust gas and deteriorating drivability.

Further, in the present embodiment, the required voltage is prevented from excessively increasing by the fuel increase correction.
It is possible to prevent the required voltage from exceeding the withstand voltage of the high tension cord 32, and to prevent its melting.

The present invention may be embodied in another embodiment shown below. (1) The calculation method of the fuel injection amount may be changed to a method other than the above embodiment. For example, the pressure in the intake passage 7 (intake pipe pressure) is detected, and the amount of intake air per engine cycle is estimated from the detected pressure and the engine speed NE.
You may change to the type (speed density method) which calculates a basic injection time based on the value. Further, the type (throttle speed method) of estimating the intake air amount per one engine cycle from the throttle opening and the engine speed and calculating the basic injection time based on the value may be changed.

(2) In the above-described embodiment, the time of the first
Although the different increment values βi and βnew are used for the subsequent and subsequent increments, the increment correction may always be performed with a constant increment value. (3) In the above embodiment, when calculating the deviation ΔV, the peak value V
Although rpeak is used, other values may be used.

(4) In the above embodiment, when calculating the injection time TAU, the wall surface adhesion correction amount FMW is increased by βi, βnew.
Is added, the increase values βi and βnew may be directly added to the basic injection time TP separately from the wall adhesion correction amount FMW.

(5) The present invention relates to an ignition system (D) which performs ignition control without using a distributor.
LI).

[0071]

As described above in detail, according to the present invention, the secondary voltage of the ignition coil at the time of discharging the spark plug is detected. The absolute value of the secondary voltage of the ignition coil when the air-fuel ratio of the air-fuel mixture reaches a predetermined value is stored in advance as a threshold value. Then, when the air-fuel ratio becomes larger than the predetermined value and the absolute value of the secondary voltage becomes larger than the threshold value, the fuel injection amount is corrected to increase. For this reason, even if the required voltage of the ignition plug and the secondary voltage of the ignition coil both increase due to the partial deviation of the air-fuel ratio in the combustion chamber, the required voltage exceeds the maximum value that the secondary voltage can take. It is possible to prevent the occurrence of misfire.

[0072] Also, so that in accordance with the deviation between the maximum value of the absolute values of the threshold and the secondary voltage, it changes the correction amount for the injection amount increase. Therefore, even if there are variations in each inner combustion engine in the waveform of the secondary voltage, it is possible to appropriately increase correction of the fuel injection amount. Further, excessive increase correction can be prevented, so that an increase in exhaust gas and a deterioration in operating performance of the internal combustion engine can be prevented.

[Brief description of the drawings]

FIG. 1 is a conceptual configuration diagram of the present invention.

FIG. 2 is a schematic configuration diagram showing an engine and its peripheral devices in an embodiment embodying the present invention;

FIG. 3 is a partially enlarged front view of the vicinity of an electrode of a spark plug in one embodiment.

FIG. 4 is an electric circuit diagram of an ignition device according to one embodiment.

FIG. 5 is a waveform chart showing a change in a secondary voltage in one embodiment.

FIG. 6 is a block diagram showing an internal configuration and the like of an ECU in one embodiment.

FIG. 7 is a flowchart showing a fuel injection control routine executed by a CPU in one embodiment.

FIGS. 8A and 8B are waveform diagrams showing a change in a secondary voltage when a fuel increase correction is performed in one embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine as an internal combustion engine, 6 ... Combustion chamber, 7 ... Intake passage, 19 ... Fuel injection valve, 23 ... Ignition coil
Reference numeral 24: primary coil, 25: secondary coil, 28: spark plug, 29: center electrode, 31: ground electrode, 37: air flow meter, 38: intake temperature sensor, 39: throttle sensor, 40: water temperature sensor, 41 ... Oxygen sensor, 42 ... Rotation speed sensor, 43 ... Reference position sensor (37 to 43 constitute operating state detecting means), 44 ... Voltage attenuator as voltage detecting means, 46 ... Injection amount calculating means, injection CPU constituting control means and injection amount correction means; 47, ROM as storage means; Vr, secondary voltage; α, threshold value;
Vrpeak: peak value as the maximum absolute value of the secondary voltage, ΔV: deviation, βi, βnew: increased value as a correction amount .

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F02D 45/00 345 F02D 41/04 330 F02D 41/14 310 F02P 17/12

Claims (1)

(57) [Claims] A fuel injection valve, which is provided in an intake passage communicating with a combustion chamber of an internal combustion engine and injects fuel into air flowing through the passage to generate an air-fuel mixture , a primary coil and a secondary coil. provided, by the current supply to the primary coil is cut off, and the ignition coil for generating a secondary voltage in the secondary coil is connected before Symbol ignition coil,
A spark plug for igniting the air-fuel mixture in the combustion chamber by discharge between electrodes by a secondary voltage from the secondary coil, operating condition detecting means for detecting operating conditions of the prior SL internal combustion engine, before <br / > SL and injection amount calculating means for calculating an injection amount from the fuel injection valve in accordance with the operating state by the operating condition detecting means, before Symbol ejection for driving and controlling said fuel injection valve such that the injection quantity by the injection amount calculating means ignition when the control means, the air-fuel ratio which is the ratio of the previous SL and voltage detecting means for detecting the secondary voltage of the ignition coil during discharge of the spark plug, the air and the fuel in the pre-Symbol mixture becomes a predetermined value Storage means for storing in advance the absolute value of the secondary voltage of the coil as a threshold ,
Before SL becomes larger than the air-fuel ratio is a predetermined value of the air-fuel mixture, the absolute value of the secondary voltage by the voltage detecting means on condition that is greater than the threshold value of the storage means, the injection amount calculating means a fuel injection control apparatus for an internal combustion engine having an injection amount correction means for increasing correction of the injection amount, the injection amount correction means, execution condition of the increasing correction engine
When first established after starting, the air-fuel ratio is set to the stoichiometric air-fuel ratio.
The injection amount calculation method has an initial increase value for approaching
While increasing the injection amount of the stage, the second time of the execution condition
When the following holds, the threshold and the absolute value of the secondary voltage are
Calculation of the injection amount with the increase value according to the deviation from the maximum value
Internal combustion engine for increasing the injection amount of a means
Fuel injection control device.