JPS6035155A - Control method of fuel injection - Google Patents

Abstract

PURPOSE:To always obtain the most suitable air-fuel ratio, by increasing the decision value of an injection amount larger as an intake pipe pressure increases when the injection amount is acceleration increased and/or asynchronously increased, when a change amount of the intake pipe pressure exceeds the predetermined decision value. CONSTITUTION:When an engine is operated, a control circuit 22 first calculates the basic injection time of fuel from outputs of an intake pipe pressure sensor 20 and a crank angle sensor 34. Next, the control circuit 22 calculates the primary and the secondary differentiated values, being the time-change amount of intake pipe pressure, under the condition that an idle switch 40, turned on when a throttle valve 18 is almost fully closed, is placed in an off-condition. And then the circuit 22 obtains a decision level for each change amount on the basis of the intake pipe pressure. These decision levels are set so as to be increased larger as the intake pipe pressure increases. Subsequently, each change amount is successively conpared with these decision levels, and on the basis of this compared result, an injection amount of fuel is acceleration increased to be corrected and/or asynchronously increased.

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 for increasing the amount of synchronous injection and/or increasing the amount of injection asynchronously in accordance with the amount of change in intake pipe pressure of an engine.

In an internal combustion engine that has a fuel injection valve and has an electronically controlled fuel injection control device that performs synchronous injection at every predetermined crank angle with a fuel injection amount calculated based on the engine load and engine speed, When the amount of acceleration of the engine is above a predetermined judgment level, the fuel injection amount during synchronous injection is increased (hereinafter referred to as acceleration increase correction). Increase fuel amount (hereinafter referred to as
(asynchronous fuel increase).

Conventionally, in internal combustion engines of the type in which this type of acceleration increase correction or asynchronous acceleration increase is performed when the amount of change in intake pipe pressure exceeds a predetermined judgment level, the judgment level has conventionally been kept constant regardless of the engine load. It is set. Therefore, the determination level for this type of increase is set to a relatively small value so that it can be easily executed when the engine load is low.

However, when the engine is under high load, the intake pulsation tends to increase (and due to this pulsation, the amount of change in intake pipe pressure may exceed the determination level, causing acceleration increase correction or asynchronous increase. It becomes richer than necessary,
This adversely affects driving performance, exhaust emissions, and fuel efficiency.

An object of the present invention is to propose a fuel injection control method that eliminates such conventional drawbacks, reduces undesired acceleration increase and/or asynchronous increase, and obtains an air-fuel ratio that is optimal for the operating condition. .

When the amount of change in intake pipe pressure is equal to or greater than a predetermined judgment value, the injection quantity in synchronous injection is accelerated and increased and/or the injection quantity is increased asynchronously. (characterized by)

According to the present invention, the synchronous acceleration increase and/or the asynchronous increase during engine acceleration are not performed undesirably in a high load region, so an air-fuel ratio optimal for the operating condition can be obtained, and exhaust emissions and fuel efficiency can be improved.

In addition, in the following examples, the fuel injection amount is expressed in terms of time, but the fuel injection time and the fuel injection amount are used to mean exactly the same thing.

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 is an engine body, 12 is an intake passage,
Reference numeral 14 indicates a combustion chamber, and reference numeral 16 indicates 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 the opening/opening 1 circuit 22 via a signal line β1, 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 the signal wire 2, 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, and a signal line 2
3, the pressurized fuel sent from a fuel supply system (not shown) is controlled to open and close in response to electrical drive pulses supplied from the control circuit 22 through the intake valve 25, and into the intake passage 12 near the intake valve 25.
That is, it is intermittently injected into the intake boat section. The exhaust gas after being burned in the combustion chamber 14 is passed through the exhaust valve 28 and the exhaust vent Nr1.
6 and three-way catalytic converter 30 to the atmosphere.

Crank angle sensors 34 and 36 are attached to the distributor 32 of the engine, and these sensors 3
4.36 is signal line I! , 4, control circuit 22 via ℃5
It is connected to the. These sensors 34 and 36 output pulse signals each time the crankshaft rotates 30 degrees and 360 degrees, and these pulse signals are connected to the signal lines 14 and i5.
are supplied to the control circuit 22 via each of them.

Distributor 32 is connected to igniter 38,
The igniter 38 is connected to the control circuit 22 via a signal line β6.

Reference numeral 40 indicates an idle switch (L) that is linked to the throttle valve 18 and is closed when the throttle valve 18 is fully closed.
L switch), and is connected to the control circuit 22 via the signal line L7.
is connected to.

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. O! generates output voltage! A sensor 42 is provided, and its output signal is connected to the control circuit 22 via the signal line 18. The three-way catalytic converter 30 is connected to this 02 sensor 4.
2, and simultaneously purifies the three harmful components of exhaust gas, HC, Co, and NOx.

Further, reference numeral 44 is a water temperature sensor that detects the engine cooling water temperature and generates a voltage according to the temperature, and is attached to the cylinder/double block 46 and connected to the control circuit 22 via the signal line β9. has been done.

As shown in FIG. 2, the control circuit 22 includes a central processing unit (CPU) 22a that controls various devices, a lj-only memory ()tOM) 22b in which various numerical values and programs are written in advance, and a memory ()tOM) 22b that controls the calculation process. Random access memory () where numbers and flags are stored in predetermined areas
It has tAM-22C1 analog multiplexer function,
A/L that converts analog input signals into digital signals)
Converter (ADC) 22d1 Input/output interface (Ilo) 22e to which various digital signals are input, Input/output interface (Ilo) 22f to which various digital signals are output, Backup memory that is supplied with power from the auxiliary power source and retains memory when the engine is stopped (BU-RA
M) 22g, and path lines 22h to which these devices are respectively connected.

The R,0M22b contains a main processing routine program, an interrupt processing routine program for calculating the fuel injection pulse width, an interrupt processing routine program for calculating coefficients such as the air-fuel ratio feedback correction coefficient, an asynchronous routine program, and various other programs. Programs and the essential data necessary for their arithmetic processing are stored in advance.

The pressure sensor 20, intake temperature sensor 21°O, sensor 42, and water temperature sensor 44 are connected to the A/D converter 22d, and voltage signals 81, 82, S3,
S4 is sequentially converted into a binary signal according to instructions from the CPL 122a.

Pulse signal S5 every 30 degrees of crank angle from crank angle sensor 34, crank angle 3 from crank angle sensor 36
A pulse signal S6 every 60 degrees and an idle signal S7 from the idle switch 40 are each taken into the control circuit 22 via the l1022e. 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. Further, it is determined based on the idle signal S7 whether the throttle valve 18 is substantially fully closed.

From l1022f, a fuel injection signal S8 and an ignition signal S9 formed by various calculations are output to the fuel injection valves 26a to 26d and the evening knife 38, respectively.

In an internal combustion engine equipped with a fuel injection control device to which the method of the present invention configured as described above is applied, fuel is injected according to the routine programs shown in FIGS. 3, 3, and fQ.

The synchronous injection routine shown in FIG. 3 is a crank angle interrupt routine activated by the above-mentioned interrupt request signal, and in step 81, the map shown in FIG. The basic fuel injection time TP is calculated from. Next, in step S2, the idle signal S
7, it is determined whether the idle switch 40 is open, in other words, whether the throttle valve 18 is not substantially fully closed.

When it is determined that the throttle valve 18 is not substantially fully closed,
In step S3, ΔPM and ΔΔPM, which are the amount of change in intake pipe pressure PM over time, are calculated.

ΔPM is determined by the difference between the intake pipe pressure PM, which is sequentially taken into CP[J at a predetermined period, and PMi+□, and ΔΔP
M is ΔPMi and ΔPM determined sequentially in this way.
It can be determined by the difference between , ya, and . ΔPM is the first-order differential value of the intake pipe pressure PM with respect to time, and ΔΔPM is also the second-order differential value.

) tOM22 b contains a graph of intake pipe pressure PM and judgment level ) tPl as shown by the solid line in FIG.
2 graph is written in advance.

These judgment levels RPI and RP2 are based on the intake pipe pressure PM
(It is set so that it gets bigger as it gets thicker.)

Here, when step S4 is executed, the first differential value ΔP is calculated based on the intake pipe pressure PM according to the graph shown in FIG.
Determination level RPI for M and determination level RP2 for second-order differential value ΔΔPM are determined.

In addition, )tOM22b contains a graph showing the relationship between the second-order differential value ΔΔPM and the correction coefficient α as shown in FIG. 6, and a graph showing the relationship between the first-order differential value ΔPM and the correction coefficient β as shown in FIG.
A graph showing the relationship is also included in advance.

Here, in step S5, it is determined whether the second-order differential value ΔΔPM is equal to or higher than the determination level LP2, and if an affirmative determination is made, the process proceeds to step 86. In step S6, a correction coefficient α is determined based on the second-order differential value ΔΔPM according to the graph of FIG. 6, and the process proceeds to step S7. In step S7, the correction coefficient f2 is set to (l + α
) and store its value in a given chain acid.

On the other hand, if a negative determination is made in step S5, it is determined in step S8 whether the negative order differential value ΔPM is equal to or higher than the determination level RPI. If an affirmative determination is made (lυ), in step S9, according to the graph in FIG. 7, a correction coefficient β is determined based on the negative order differential value ΔPM, and the process proceeds to step 810.
Store the value in a predetermined area.

In step Srl, the larger value of the correction coefficients f1 and f2 is set as the true acceleration increase correction coefficient f. In step 812, the basic fuel injection time TP is corrected by the acceleration increase correction coefficient f added in this way and the engine cooling water temperature, intake temperature, etc. calculated by another routine (not shown). The final fuel injection time τ is determined by multiplying the coefficient or the correction coefficient including the air-fuel ratio feedback correction coefficient by .

On the other hand, if a negative determination is made in step S8, step 813
, a predetermined number C1 is subtracted from the correction coefficient fl, and the result is set as a new correction coefficient f1.

Further, in step J@814, a predetermined number c2 (c2>clJ) is subtracted from the correction coefficient f2, and the result is set as a new correction coefficient f2.Then, in step 815 (12), the correction coefficient f2 or II It is determined whether or not it is greater than or equal to 1", and if it is less than 1", the correction coefficient f2 is set to
1". Then, in step 817, it is determined whether or not the correction coefficient f1 is greater than or equal to n 1 rr. If the determination is affirmative, the process proceeds to step 811, where the same process as described above is performed. In step S17, the determination is negative. Then, in the hand JIi818, the acceleration increase correction coefficient f and the correction coefficient f1 are set to "I".
As II, the process proceeds to step 812 and the injection time τ is determined.

On the other hand, if the throttle valve 18 is fully closed and a negative determination is made in step S2, in step 520A, the correction coefficient f1,
Set f2 to "1" and proceed to step 71iiifS14 to calculate the injection time τ. In this case, acceleration increase correction is not performed.

That is, according to the synchronous injection routine of FIG. 3, when the throttle valve 18 is not fully closed, the first differential value ΔPM and the second differential value ΔΔP of the intake pipe pressure PM with respect to time
Calculate M, search the map for tPl and RP2 (judgment level that increases as the intake pipe pressure PM increases), and first, if the second-order differential value ΔΔPM is equal to or higher than the determination level RP2,
The correction coefficient α is set according to the second-order differential value ΔΔPM. Next, the correction coefficient f2 is set to (1+α), and the larger value of the correction coefficient f1 and the correction coefficient f2 for the first-order differential value ΔPM stored in a predetermined storage area is set as the acceleration increase correction coefficient f.
Then, the fuel injection time τ is determined by this acceleration increase correction coefficient f.

If the second-order differential value ΔΔPM becomes smaller than the judgment level 1 (P2), and the negative-order differential value ΔPM becomes thicker than the judgment level RPI (then the correction coefficient β
is set, and the correction coefficient f1 for the -order differential value is set as When both the value ΔPJ and the second-order differential value ΔΔPM become smaller than the determination level, each correction coefficient fl, 12 is subtracted by a predetermined value. In this embodiment, the correction coefficient f2 is first
l# or less, at that time, the correction coefficient f2 is forcibly set to "
171, and thereafter, the value of the correction coefficient f1 is used as the acceleration increase correction coefficient f. Then, the correction coefficient fx is I
When it becomes smaller than I II II, both the correction coefficient f1 and the acceleration increase correction coefficient f become LL I LL. Therefore, in this case, acceleration increase correction is not performed.

Here, the first-order differential value Δ when the intake pipe pressure PM changes
PM and second-order differential value ΔΔPM are as shown in FIG. 8 (N to (D)).

Next, the asynchronous increase routine will be explained with reference to FIG.

This asynchronous fuel increase routine is a time interrupt routine that is activated at a predetermined cycle, and in step S21, it is determined based on the idle signal S7 whether the throttle valve 18 is substantially fully closed. If an affirmative determination is made, in step 822, the second differential value ΔΔPM of the intake pipe pressure PM with respect to time is determined.
Calculate. Then, in step 823, the determination level LP2 is set in the same manner as step S4 in FIG. Next, in step S24, it is determined whether the second-order differential value ΔΔPM is equal to or higher than the determination level RP2. If the determination is affirmative, in step S25, "l#" is set to the asynchronous request 7 representing the asynchronous injection request (15), and this routine is ended.

If a negative determination is made in steps 821 and 824, no asynchronous injection request is issued (this routine is ended).

Figure 10 shows the main routine program, step 83.
1, it is determined whether or not it is the timing for synchronous injection based on the 30-degree crank signal S5 and the 360-degree crank signal S6. If it is the injection timing, in step 832, the fuel injection time τ determined by the synchronization routine is set in a down counter (not shown), and the injection signal S8 is sent to the injection valve 2.
6 and performs injection. Injection ends when the down counter reaches zero.

If a negative determination is made in step 831, the process advances to step S33. In step S33, it is determined whether there is an asynchronous injection request based on the contents of the asynchronous request flag.

If the flag is set to rr 1 u, step 834
In this step, asynchronous injection is performed in the same manner as synchronous injection. The injection amount at that time corresponds to a predetermined time (16) τASY. Note that the asynchronous injection may not be performed immediately when an asynchronous request is issued, but the amount of the asynchronous request may be added at the time of the next synchronous injection.

When correcting the acceleration increase in synchronous injection, it may be possible to judge only whether the -order differential value ΔPM exceeds the judgment level, and to correct the acceleration increase only when it exceeds the judgment level. As in the example, if PM and second-order differential value ΔΔPM are used for the negative-order differential value, the result in FIG. 8 (7I
! As shown at ~0, ΔΔPM exceeds the level before ΔPM, so faster acceleration increase correction can be performed.

The basic fuel injection time may be determined based on the intake air amount and the engine speed instead of the basic fuel injection time based on the intake pipe pressure and the engine speed.

Further, the determination level may be changed in accordance with the intake pipe pressure only when determining synchronous acceleration increase correction or only when determining asynchronous increase.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of an internal combustion engine having a fuel injection control device to which the method of the present invention is applied, Fig. 2 is a block diagram showing a detailed example of the control circuit, and Fig. 3 is a block diagram showing a detailed example of the control circuit. A flowchart showing an example of a synchronous injection routine according to
FIG. 4 is a diagram showing a map of basic fuel injection time, and FIG. 5 is a diagram showing the determination level RPI. Graph showing RP2, FIG. 6 is a graph showing the relationship between ΔΔPM and correction coefficient α, FIG. 7 is a graph showing the relationship between ΔPM and correction coefficient β, 8th factor 4 to (D) are idle signals,
A time chart showing intake pipe pressure, a negative differential value ΔPM, and a second differential value ΔΔPM, FIG. 9 is a flowchart showing an example of an asynchronous request route according to the method of the present invention, and FIG. It is. lO... Engine body, 18... Throttle valve, 20.
...Intake pipe pressure sensor, 22...Control circuit, 26...
・Injection valve, 34・36...Crank angle senna, 40・
...Idle switch. Agent Tatsuyuki Unuma (and others) Winter sweat and stomach and iν 屹→t To run Figure 6 2 vt kL minutes ΔPM Figure 7 (B) 1 measure l reform 84 ΔPM Figure 8 Figure 9 Figure 10

Claims (4)

[Claims] (1) When performing synchronous injection at every predetermined crank angle and performing asynchronous fuel increase regardless of the crank angle position, calculate the fuel injection amount of the synchronous injection based on the engine load and engine speed, The amount of change in the intake pipe pressure of the engine is calculated, and the calculated amount of change is set so that the larger the intake pipe pressure is, the thicker it becomes. As a result, when the amount of change in the intake pipe pressure is larger than the determination value, the fuel injection amount is corrected to increase the acceleration amount, and/
Or a fuel injection control method characterized by executing an asynchronous increase. (2) The fuel injection control method according to claim 1, wherein the engine load is intake pipe pressure or intake air amount. (3) The fuel injection control method according to claim 1 or 2, wherein the engine acceleration amount is a first-order differential value or a second-order differential value with respect to a time change in intake pipe pressure. (4) The fuel injection control method according to any one of claims 1 to 3, wherein the determination value is set for each of synchronous injection and asynchronous fuel increase.