JPH0477138B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection control method, and more particularly to a fuel injection control method suitable for use in a vehicle internal combustion engine, in which the amount of fuel injection is calculated based on engine load and engine speed. It is something.

In such a vehicle internal combustion engine, fuel is injected at the fuel injection amount calculated as described above in synchronization with a predetermined crank angle position, and on the other hand, the amount of acceleration of the engine is detected at regular intervals. A transient state is determined, and a non-periodic increase in dosage is performed when the transient state is present. If each time a transient state is determined, asynchronous injection is performed according to the asynchronous increase regardless of the crank angle position at that time, the injection amount between each cylinder of the engine will tend to vary, and the acceleration shock will be affected. There is a risk that various problems will occur, such as yawuri and a decrease in acceleration response. Such variations in fuel amount are also affected by the engine speed, since the asynchronous request determination routine is activated at predetermined time intervals regardless of the crank angle.

SUMMARY OF THE INVENTION An object of the present invention is to solve such conventional problems and to propose a fuel injection control method that reduces variations in injection amount between cylinders due to asynchronous injection.

The present invention calculates the amount of fuel injection based on the engine load and engine speed, performs synchronous injection in an amount corresponding to the amount of fuel in synchronization with a predetermined crank angle, and responds to transient operation of the engine. In a fuel injection control method that performs a predetermined amount of asynchronous injection regardless of the crank angle, the amount of acceleration of the engine is calculated,
When the amount of acceleration is greater than or equal to a predetermined reference value, it is determined that it is an asynchronous request during transient operation, and asynchronous injection is executed at the first asynchronous request among consecutive asynchronous requests, and at the second and subsequent asynchronous requests. For the asynchronous request before the synchronous injection signal is generated, the predetermined amount is added every time the determination is made, and the addition result is added to the fuel injection amount for the next synchronous injection, and the injection is performed, and then the synchronous injection is performed. The predetermined amount is added to the asynchronous request generated during the signal generation every time the determination is made, and the addition result is added to the fuel injection amount at the time of the next synchronous injection and the injection is performed. do.

The technical problem of the present invention can be solved by integrating the injection amount corresponding to the number of requests for asynchronous injection into the next synchronous injection amount. Since asynchronous injection is performed, transient response can be improved.

Engine load is, for example, intake pipe pressure, intake air amount,
It can be expressed by the amount of accelerator depression and the opening degree of the throttle valve, and the acceleration amount of the engine can be expressed by, for example, the amount of change over time in the intake pipe pressure, the amount of accelerator depression, and the opening degree of the throttle valve.

Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 1 shows an example of an electronically controlled fuel injection type internal combustion engine to which the present invention is applied, in which reference numeral 10 indicates an engine body;
Reference numeral 2 indicates an intake passage, 14 a combustion chamber, and 16 an exhaust passage. An intake pipe absolute pressure sensor 20 provided in the intake passage 12 downstream of the throttle valve 18 is connected to a control circuit 22 via a signal line l1, and generates a voltage according to the intake pipe absolute pressure. The intake air temperature sensor 21 is provided in the intake passage 12 upstream of the throttle valve 18, is connected to the control circuit 22 via a signal line l2, and generates a voltage according to the intake air temperature. Intake air is sucked in through an air cleaner (not shown) and whose flow rate is controlled by a throttle valve 18 (not shown) linked to an accelerator pedal (not shown), and is led to the combustion chamber 14 of each cylinder via a surge tank 24 and an intake valve 25.

A fuel injection valve 26 is provided for each cylinder,
The opening/closing is controlled in response to electrical drive pulses supplied from the control circuit 22 via the signal line l3, and pressurized fuel sent from a fuel supply system (not shown) is fed into the intake passage 12 near the intake valve 25, that is, the intake port. Inject intermittently into the area. The exhaust gas after being combusted in the combustion chamber 14 is discharged into the atmosphere via the exhaust valve 28, the exhaust passage 16, and the three-way catalytic converter 30.

Crank angle sensors 40 and 42 are attached to the distributor 38 of the engine, and these sensors 40 and 42 are connected to the control circuit 22 via signal lines 16 and 17. These sensors 40 and 42 output pulse signals each time the crankshaft rotates 30 degrees and 360 degrees, respectively, and these pulse signals are supplied to the control circuit 22 via signal lines l6 and l7, respectively.

The distributor 38 is connected to an igniter 39, and the igniter 39 is connected to the control circuit 22 via a signal line l8.

The reference numeral 44 designates an idle switch (LL switch) that operates in conjunction with the throttle valve 18 and is closed when the throttle valve 18 is substantially fully closed, and is connected to the control circuit 22 via a signal line l8a. .

The exhaust passage 16 outputs a signal responsive to the oxygen concentration in the exhaust gas, that is, a signal with two different values depending on whether the air-fuel ratio is on the lean side or rich side with respect to the stoichiometric air-fuel ratio. _O2 that generates the output voltage
A sensor 46 is provided, the output signal of which is connected to the signal line l.
It is connected to the control circuit 22 via 9. The three-way catalytic converter 30 is provided downstream of the O ₂ sensor 46 and simultaneously purifies three harmful components, HC, CO, and NOx, in the exhaust gas.

Further, reference numeral 48 detects the engine cooling water temperature,
This is a water temperature sensor that generates a voltage according to the temperature, and is attached to the cylinder block 50 and connected to the control circuit 22 via a signal line l10.

As shown in FIG. 2, the control circuit 22 includes a central processing unit (CPU) 22a that controls various devices;
It has a read-only memory (ROM) 22b in which various numerical values and programs are written in advance, a random access memory (RAM) 22c in which numerical values and flags in the calculation process are written in a predetermined area, and an analog multiplexer function, and can accept analog input signals. A/D converter (ADC) that converts to digital signals
22d, input/output interface (I/O) 22e to which various digital signals are input, input/output interface (I/O) 22f to which various digital signals are output, is supplied with power from the auxiliary power source and retains memory when the engine is stopped. It is composed of a backup memory (BU-RAM) 22g, and a bus line 22h to which each of these devices is connected.

The ROM 22b contains a main processing routine program, an interrupt processing routine program for calculating fuel injection pulse width, an interrupt processing routine program for calculating coefficients such as air-fuel ratio feedback correction coefficients,
A synchronous routine program, an asynchronous routine program, and other various programs to be described later, as well as various data necessary for their arithmetic processing, are stored in advance.

Then, a pressure sensor 20, an intake temperature sensor 21,
The O ₂ sensor 46 and the water temperature sensor 48 are connected to the A/D converter 22d, and voltage signals S1, S2, S3, S4 from each sensor are sequentially converted into binary signals according to instructions from the CPU 22a.

A pulse signal S5 for every 30 degrees of crank angle from the crank angle sensor 40, a pulse signal S6 for every 360 degrees of crank angle from the crank angle sensor 42, and an on/off signal S7 from the idle switch 44 respectively control the I/O 22e. The signal is taken into the post-control circuit 22 via the control circuit 22. A binary signal representing the engine speed is formed based on the pulse signal S5, and the pulse signals S5 and S6 work together to generate an interrupt request signal for fuel injection pulse width calculation, a fuel injection start signal, a cylinder discrimination signal, etc. is formed.

From the I/O 22f, a fuel injection pulse signal S10 and an ignition signal S11 formed by various calculations are
They are output to the fuel injection valves 26a to 26d and the igniter 39, respectively.

In the internal combustion engine to which the method of the present invention configured as described above is applied, synchronous injection is performed according to the synchronous injection routine shown in FIG.

Fig. 3 is activated by the above-mentioned interrupt request signal that occurs at every predetermined crank angle, and in step S1, the basic fuel injection time TP is calculated based on the intake pipe pressure PM and the engine speed NE. Various correction calculations are performed on the basic fuel injection time TP to determine the final fuel injection amount τ.
Then, in step S2, the combustion injection amount τ is
The asynchronous addition Στ _ASY determined in the routine shown in FIG.
6. Set the valve opening time and injection end time. As a result, the injection valve 26 is opened for a predetermined period of time. Next, in step S4, the asynchronous addition Στ _ASY is set to zero and this routine ends.

The asynchronous injection is executed by the asynchronous injection routine shown in FIG. 4, which is a time interrupt routine at predetermined intervals, for example, every 30 ms. First, in step S11, it is determined whether the first-order differential value ΔPM according to the time change of the intake pipe pressure PM is equal to or higher than a predetermined determination level R. If an affirmative determination is made, in step S12, the flag FLG is “1” or not.
If “0” is set, it is the first asynchronous request among consecutive asynchronous requests, and step S13
, a predetermined amount of asynchronous injection τ _ASY
The injection signal S10 is generated in accordance with the injection signal S10 to drive the injection valve 26, thereby executing asynchronous injection. Then the steps
In S14, the flag FLG is set to "1".
If a negative determination is made in step S11, a flag is set in step S16.
Set FLG to “0”.

If the flag FLG is determined to be "1" in step S12, the asynchronous request determined in step S11 is the second or subsequent asynchronous request among consecutive asynchronous requests, and the The asynchronous injection amount τ _ASY is added to obtain Στ _ASY , and this routine ends.

As described above, according to one procedure example of the method of the present invention, when a request other than the first asynchronous request among consecutive asynchronous injection requests is made, a predetermined amount of asynchronous injection is accumulated without executing the asynchronous injection, The cumulative amount of fuel will be injected during the next synchronous injection. Further, an asynchronous injection request during synchronous injection was also processed in the same way.

An example of such a method of the present invention is shown in FIG.
This will be explained in detail with reference to B.

In the figure, τ1 to τ3 indicate synchronous injection, and a to h
indicates an asynchronous injection request. When asynchronous injection requests a, b, and c are issued in succession, first, asynchronous injection τ _ASY 1 is executed in response to the first asynchronous request a,
The asynchronous injection portions of the other asynchronous requests b and c are integrated and expressed as Στ _ASY , and are injected together with the next synchronous injection τ2. If asynchronous requests d and e are issued consecutively to a, b, and c during this second synchronous injection, the following three
Στ _ASY is executed in step S1 of FIG. 4 in order to add it to the synchronous injection τ3 of the second time. Then, when the continuous asynchronous requests stop and the next first asynchronous request f is issued, the asynchronous injection τ _ASY 2 is executed in response to that request, and the next consecutive asynchronous request g, When h is issued, the previous asynchronous requests d, e
Similarly, Στ _ASY to be added in the third synchronous injection τ3 is executed in step S15 of FIG. 4.

Therefore, during the second synchronous injection, the asynchronous requests b and c are simultaneously injected, and during the third synchronous injection, the asynchronous requests d, e, g, and h are simultaneously injected. In addition, in a state where there are no asynchronous requests f, g, and h in Fig. 5A and B, that is, in a state where the speed is decelerated from acceleration to constant speed, if the asynchronous requests d and e during the second synchronous injection are Synchronous injection τ3
If additional injection is performed at the second synchronous injection τ2 without adding to , there is a possibility that a certain cylinder will suddenly go from extremely rich to lean and surging may occur. According to the control method of the present invention, in such a state where acceleration shifts to constant speed, the amount of asynchronous requests d and e is added to the third synchronous injection τ3, so the fuel injection amount is gradually reduced to prevent the occurrence of surging. This has the effect of suppressing this and improving transient response.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of a fuel injection type internal combustion engine to which the method of the present invention is applied, Fig. 2 is a block diagram showing a detailed example of its control circuit, and Fig. 3 is an example of a synchronous injection routine. Flowchart showing, No. 4
The figure is a flowchart showing an example of an asynchronous injection routine, and Fig. 5A and B show an asynchronous request and an injection signal.
These are time charts showing each S10. 10... Engine body, 20... Intake pressure sensor, 2
2... Control circuit, 26... Injection valve, 40, 42...
...Crank angle sensor.

Claims (1)

[Claims] 1 Calculates the fuel injection amount based on the engine load and engine speed, performs synchronous injection in an amount corresponding to the fuel injection amount in synchronization with a predetermined crank angle, and injects the fuel in an amount corresponding to the fuel injection amount in response to transient operation of the engine. In a fuel injection control method that performs a predetermined amount of asynchronous injection regardless of the crank angle, the amount of acceleration of the engine is calculated, and when the amount of acceleration is greater than or equal to a predetermined reference value, it is determined that an asynchronous request in transient operation has occurred. Asynchronous injection is executed at the first asynchronous request among the asynchronous requests, and the predetermined amount is added each time the asynchronous request is determined from the second time onwards until the next synchronous injection signal is generated. , during the next synchronous injection, the addition result is added to the fuel injection amount and the injection is performed, and the predetermined amount is added to the asynchronous request that occurs during the generation of the synchronous injection signal every time the determination is made, A fuel injection control method characterized by adding the addition result to the fuel injection amount and performing the injection at the time of the next synchronous injection.