JPH0454054B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a fuel injection amount control method for an internal combustion engine (hereinafter sometimes referred to as an "engine").
In particular, the present invention relates to a fuel injection amount control method for an internal combustion engine in which a fuel injection valve is provided upstream of an intake throttle valve.

[Conventional technology]

In general, in conventional fuel injection amount control methods for internal combustion engines, the basic fuel injection time, that is, the basic opening time of the injection valve is calculated based on, for example, the absolute pressure in the intake pipe and the engine rotational speed. The final fuel injection time is determined by performing various correction calculations on the time depending on the operating state of the engine, including the warm-up state and transient state of the engine.

Then, the correction according to the warm-up state of the engine is
For example, when the engine coolant temperature is below 70℃,
This is done by multiplying the basic injection amount by an increase coefficient that is determined to decrease as the temperature increases.

[Problem to be solved by the invention]

The cooling water temperature is a value that closely reflects the temperature near the engine's intake port, so for engines with fuel injection valves installed in the intake port of each cylinder, the above-mentioned increase correction is performed during warm-up. However, in engines with one fuel injection valve installed upstream of the intake throttle valve, the intake passage from the fuel injection valve to the combustion chamber is long, so the vaporization state of the fuel depends on the wall temperature of the intake passage. Therefore, if the wall temperature is not taken into consideration when making fuel increase corrections according to the warm-up state, there is a problem that the amount of fuel drawn into the combustion chamber will deviate from the optimal value, especially in extremely cold weather. .

Therefore, the present invention focuses on the fact that the intake air temperature downstream of the intake throttle valve reflects the intake passage wall temperature in the vicinity, and that the increase in intake passage wall temperature during warm-up is approximately linear. However, it is an object of the present invention to solve the above-mentioned problem by performing an appropriate amount of increase correction during warm-up by taking into account the intake air temperature in addition to the conventional cooling water temperature.

[Means to solve the problem]

A fuel injection amount control method for an internal combustion engine according to the present invention includes a fuel injection valve installed upstream of an intake throttle valve of an internal combustion engine, and an air-fuel mixture injected from the fuel injection valve and mixed with intake air into the internal combustion engine. In a fuel injection amount control method for an internal combustion engine having a relatively long intake passage leading to a combustion chamber, a basic fuel injection amount is calculated based on the rotation speed and load of the internal combustion engine, and a basic fuel injection amount is calculated based on the rotation speed and load of the internal combustion engine. The intake air is selected according to the output value at the time of startup of an intake air temperature sensor installed so as to protrude into the intake passage of the engine, and is attenuated at a predetermined period after startup regardless of the output value of the intake air temperature sensor. The basic fuel injection amount during warm-up is corrected based on a throttle valve downstream intake temperature correction value and a warm-up correction value selected according to the cooling water temperature of the internal combustion engine.

〔Example〕

FIG. 1 shows a configuration example of an internal combustion engine for an automobile to which an electronic fuel injection control device according to the present invention is applied. Air filter 1 is connected to throttle body 5 via inlet pipe 3. The throttle body 5 is provided with a fuel injection valve 7 on its upstream side, and an intake throttle valve 9 that adjusts the amount of intake air in conjunction with an accelerator pedal (not shown) is provided downstream of the fuel injection valve 7. An intake pipe absolute pressure sensor 11 is provided downstream of the throttle valve 9 to measure the absolute pressure at that location. Furthermore, there is a valve opening position sensor 2 that measures the opening position of the intake throttle valve 9, an idle switch 4 that is turned on only when the intake throttle valve 9 is fully closed, and a valve opening position sensor 2 that measures the opening position of the intake throttle valve 9. 40
A power switch 6, which is turned on only when the temperature exceeds the temperature, is attached in conjunction with the intake throttle valve 9.

The throttle body 5 includes an intake manifold 1 having branch pipes connected to each cylinder of the engine.
3, and the intake manifold 13 has
An intake temperature sensor 15 is provided to measure the temperature of the intake air. A riser portion 17 is provided on the bottom wall 13a of the intake manifold 13 before branching, through which engine cooling water is circulated to heat the air-fuel mixture.

19 is a well-known engine body, and piston 2
1, a cylinder 23, and a cylinder head 25 define a combustion chamber 27. The air-fuel mixture is sucked into the combustion chamber 27 through an intake valve 29, and the air-fuel mixture flows into the air plug 3.
ignited by 1. A water jacket 33 is formed around the cylinder 23, and engine cooling water is circulated through the water jacket 33 to cool parts including the cylinder 23. An engine coolant temperature sensor 37 is provided on the outer wall of the cylinder block 35 to measure the temperature of the engine coolant in the water jacket 33.

An exhaust manifold 39 is connected to an exhaust port (not shown) of the cylinder head 25, and on the downstream side thereof, the residual oxygen concentration in the exhaust gas is measured.
An O ₂ sensor 41 is provided. The exhaust manifold 39 is connected to an exhaust pipe 45 via a three-way catalyst 43.

47 is a transmission connected to the engine main body 19, and a vehicle speed sensor 49 is attached thereto to measure the speed of the vehicle based on the number of revolutions of its final output shaft.
Also, 51 is a key switch, 53 is an igniter,
55 is a distributor, and the distributor 55 is provided with a Ne sensor 57 that outputs an on/off signal at every predetermined crank angle θ1, and the output signal determines the engine rotation speed and the predetermined crank angle position. In addition, a G sensor 59 is provided which outputs an on/off signal at every angle θ2 larger than the angle θ1, and cylinder discrimination and top dead center position detection are performed based on the output signal. Further, 60 indicates battery.

The control circuit 61 includes a valve opening position sensor 2, an idle switch 4, a power switch 6, an intake pressure sensor 11, an intake temperature sensor 15, an engine coolant temperature sensor 37, an O ₂ sensor 41, a vehicle speed sensor 49, a key switch 51, and a Ne sensor. 57, G sensor 59 and battery 60, respectively, and are connected to valve opening signal S1, idle signal S2, power signal S3,
Intake pressure signal S4, intake temperature signal S5, water temperature signal S6, air-fuel ratio signal S7, vehicle speed signal S8, ignition signal
S9, engine speed signal S10, cylinder discrimination signal S11
and battery voltage signal S14 are input from each sensor. The control circuit 61 is also connected to the fuel injection valve 7 and the igniter 53, and based on predetermined calculations, the control circuit 61 outputs a fuel injection signal S12 and an ignition signal.
Output S13.

As shown in FIG. 2, the control circuit 61 includes a central processing unit (CPU) 61a that controls various devices;
A read-only memory (ROM) 61b in which various numerical values and programs are written in advance, a random access memory (RAM) 61c in which numerical values and flags for calculation processes are written in predetermined areas, and an analog input signal that converts analog input signals into digital signals. A D converter (ADC) 61d, an input/output interface (I/O) 61e to which various digital signals are input and output, and a backup memory (BU) which is supplied with power from the auxiliary power source and retains memory when the engine is stopped. -RAM) 61f, and bus line 61g to which each of these devices is connected.
It consists of The program described below is
It is written in the ROM 61b in advance.

In the engine described above, fuel is injected according to the flowchart shown in FIG. Referring to FIG. 3, in step P1, the engine speed Ne is read based on the engine speed signal S1, which is a reference position signal, and the intake pipe pressure signal S4 is read.
Read the intake pipe pressure PM based on. In step P2, based on the rotational speed Ne and the intake pipe pressure PM,
The basic injection time TP is determined from the map shown in FIG. 4, and in step P3, a correction calculation process is executed according to the operating conditions of the engine to determine the corrected injection time τ.

Here, the calculation of the corrected injection time τ by the correction calculation process in step P3 will be described in detail.

The injection time τ is generally determined by the following formula.

τ=TP×FWL×FAF×(1×FTC)×FTHA
...(1) Where: TP = Basic fuel injection time FWL = Warm-up increase coefficient FAF = Air-fuel ratio feedback correction coefficient FTC = Transient air-fuel ratio correction coefficient FTHA = Intake temperature correction coefficient Therefore, the τ calculation routine shown in Fig. 5 Each coefficient is calculated based on , and the injection time τ is determined.
That is, in step P11, the warm-up increase coefficient FWL is calculated, in step P12, the air-fuel ratio feedback correction coefficient FAF is calculated, in step P13, the transient air-fuel ratio correction coefficient FTC is calculated,
In step P14, calculate (TNA+k) and calculate the correction coefficient.
Ask for FTHA. Then, in step P15, the above equation (1) is calculated.

Before explaining each calculation process in steps P11 to P13, let us explain the starting temperature correction value, which is a feature of the present invention.
An example of the ADD calculation process and an example of the intake pipe pressure PM calculation process will be described.

(Calculation process of starting temperature correction value ADD) At a predetermined timing, the correction value ADD shown in Fig. 6 is calculated.
When the arithmetic processing routine is started, first step P21 is executed.
It is determined whether the engine is starting or not. This determination is performed based on the engine rotational speed signal S10. If an affirmative determination is made, that is, if starting is in progress, then in step P22, the intake temperature signal S5 at that time is
Read the starting intake air temperature THA as the engine starting temperature based on . Next, in step P23, ROM6
The correction value shown in FIG. 7 written in advance in 1b
From the map of ADD and intake air temperature THA, a correction value ADD is read based on the read starting intake air temperature THA. In step P24, the read correction value
It is determined whether a certain period in which ADD should be attenuated by a predetermined number α has elapsed, and if an affirmative determination is made, the process proceeds to step P25. In step P25, (ADD-α) is calculated and the result is stored in a predetermined storage area as a new correction value ADD. Next, in step P25, it is determined whether the correction value ADD is smaller than zero, and if the judgment is affirmative, the correction value ADD is set to zero in step P27 and the ADD calculation routine is ended, and if the judgment is negative, step P27 is skipped. Immediately terminate the ADD calculation routine. When this routine is started after the engine has been started, a negative determination is made in step P21 and the process jumps to step P24, and if an affirmative determination is made in that step, steps P25 to P27 are executed.
If the determination is negative, steps P25 to P27 are skipped and the series of steps ends.

As mentioned above, the intake temperature at engine start
Starting temperature correction value ADD read based on THA
is attenuated by a constant number α every predetermined period as shown in FIG. This corresponds to the wall temperature at startup by taking advantage of the fact that the wall temperature of the intake passage gradually rises as the warm-up time passes, but the rise is almost linear. This is done by predicting the intake passage wall temperature at any given time during warm-up as a function of elapsed time based on the intake air temperature.

(Calculation process of intake pipe pressure PM) The calculation process of intake pipe pressure PM shown in FIG. 9 is repeatedly executed at predetermined intervals as shown in FIG. Convert the pipe absolute pressure signal S4 to a digital value and follow step P32
The value PMj is sequentially stored in registers R ₀ to _{R 3} at predetermined intervals. Next, in step P33, for example, the intake pipe pressure PM _-4 stored in the register R ₁ at time t-4 is calculated from the intake pipe pressure PM -2 stored in register R ₃ at time _t -2. Subtract and store the subtraction result DPM ₂ in register DR ₂ . Then, the process proceeds to step P34, and for example, at time t ₀ , DPM ₀ stored in register DR ₀ is stored in register DR ₁ .
Subtract DPM ₁ and store the subtraction result DDPM in register DDR. In step P35, register
Compare the second differential value DDPM of the intake pipe pressure PM stored in the DDR with the reference value REF ₁ , and find that DDPM>
If REF ₁ , jump to an asynchronous injection routine (not shown). If DDPM<REF1, end this procedure.

In this way, the intake pipe pressure PM stored in each register at each point in time is used to calculate the basic fuel injection time TP, and the one-time differential value DPM of the intake pipe pressure PM is used to calculate the synchronous acceleration increase. The second differential value DDPM is used to calculate the asynchronous acceleration increase.

Next, the calculation processing of each coefficient in each procedure of FIG. 5 will be explained.

Calculation process for warm-up increase coefficient FWL An example of the calculation procedure for warm-up increase coefficient FWL is shown in Part 11.
As shown in the figure. In step P41, the engine cooling water temperature THW is read based on the water temperature signal S6, the engine speed Ne is read based on the engine speed signal S10, and the correction value calculated by the routine shown in FIG. 6 is read.
Also loads ADD. In step P42, a correction coefficient FWLφ is determined from a map of engine cooling water temperature and correction coefficient FWLφ shown in FIG. 12, based on the latest water temperature THW that has been read. Next, in step P43,
Based on the latest engine speed Ne read,
Engine speed Ne and correction coefficient shown in Figure 13
Calculate the correction coefficient KWL from the map with KWL. Then, in step P44, the calculation of (correction coefficient FWLφ+correction value ADD)×correction coefficient KWL+1.0 is executed to obtain the warm-up increase coefficient FWL, and this series of steps ends.

Calculation Process of Feedback Correction Coefficient FAF An example of the calculation procedure of the feedback correction coefficient FAF is shown in FIG.

Air-fuel ratio feedback correction coefficient shown in Figure 14
When the FAF calculation routine is activated, it is determined in step P51 whether or not a feedback condition is satisfied. For example, the feedback control conditions are met when the engine is not in a starting state, is not increasing power after startup, the engine coolant temperature THW is 40°C or higher, is not increasing power, and is not under lean control.
If the conditions for feedback control are not satisfied, set the feedback correction coefficient FAF in step P52.
1.0 so that feedback control is not executed, and this process ends. If the conditions are satisfied, proceed to step P53.

In step P53, the air-fuel ratio signal S7 is read. procedure
In P54, the voltage value of the air-fuel ratio signal S7 is compared with the reference value REF2, and if the signal S7 is larger than the reference value REF2, it is determined that the air-fuel ratio is too rich and steps are taken to make the air-fuel ratio lean. Execute. i.e. step P55
The flag CAFL is set to zero and the process proceeds to step P56, where it is determined whether the flag CAFR is zero. When moving to the over-concentrated side for the first time, the flag CAFR is zero, so the procedure
Proceeding to P58, a predetermined value α1 is subtracted from the correction coefficient FAF stored in the RAM 61C, and the result is set as a new correction coefficient FAF. In step P59,
Set flag CAFR to 1. Therefore, if excessive concentration is determined twice or more in succession in step P54, a negative determination will always be made in step P56 passed from the second time onwards, and in step P57, a predetermined value β1 is subtracted from the correction coefficient FAF, and the The FAF calculation is ended using the result as a new correction coefficient FAF.

On the other hand, if the signal S7 is smaller than the reference value REF2 in step P54, it is determined that the air-fuel ratio is lean, and a procedure to make the air-fuel ratio rich is executed. That is, in step P90, the flag CAFR is set to zero, and the process proceeds to step P91, where it is determined whether or not the flag CAFL is zero. A flag is set when the transition to the dilute side occurs for the first time.
Since CAFL is zero, proceed to step P92 and set the correction coefficient.
A predetermined value α2 is added to FAF, and the result is set as a new correction coefficient FAF. In step P93, the flag
Let CAFL be 1. Therefore, if it is determined that it is diluted twice or more consecutively in step P54, a negative determination will be made in step P91 that passes from the second time onwards, and the procedure
In P94, a predetermined value β2 is added to the correction coefficient FAF, and the result is set as a new correction coefficient FAF.
Finish the calculation.

In addition, α1 in steps P57, P58, P92, and P94,
α2, β1 and β2 are predetermined values.

The feedback correction coefficient FAF obtained by this calculation procedure is shown in FIG. 15 together with the air-fuel ratio signal S7. Referring to this figure, signal S7 is the reference value
When the signal S7 becomes larger than REF2 or smaller than the reference value REF2, the correction coefficient FAF is first skipped by α1 or α2, and then, if the signal S7 is greater than or equal to the reference value, a predetermined number β1 is sequentially subtracted, and the signal S7 is If it is below the reference value, a predetermined number β2 is added one after another.

Calculation Process of Transient Air-Fuel Ratio Correction Coefficient FTC An example of the calculation procedure of the correction coefficient FTC is shown in FIG. 16. In this embodiment, only the correction coefficient FTC in the acceleration increase during warm-up is considered. procedure
At P61, the amount of change DPMk in the intake pipe pressure PM obtained by the routine shown in FIG. 9 is read. Step P62
Now, based on the change amount DPMk, a correction coefficient △FTCφ is determined from a map of the change amount DPMk shown in FIG. 17 and the warm-up acceleration correction coefficient △FTCφ based on the intake pipe pressure change amount. Then, in step P63,
The correction coefficient ΔFTCφ obtained in step P62 is added to the correction coefficient FTCφ that has already been obtained, and the process proceeds to step P64 using the addition result as a new correction coefficient FTCφ. In step P64, the obtained correction coefficient
It is determined whether a certain period for attenuating FTCφ by a predetermined number α has elapsed, and if an affirmative determination is made, the process proceeds to step P65. In step P65, (FTCφ-γ) is calculated and the result is stored in a predetermined storage area as a new correction coefficient FTCφ. Next, in step P66, it is determined whether the correction coefficient FTCφ is smaller than zero, and if the judgment is affirmative, the correction coefficient FTCφ is set to zero in step P67, and the process proceeds to the next step P68. If a negative determination is made in step P64 or step P66, the process also jumps to step P68.

In step P68, the engine coolant temperature THW is read based on the water temperature signal S6, and in step P69, based on this coolant temperature THW, the warm-up acceleration correction coefficient according to the coolant temperature THW and water temperature shown in FIG. 18 is calculated.
Read the correction coefficient KTC from the map with KTC. Next, in step P70, the starting temperature correction value ADD obtained in the routine shown in Fig. 6 is read, and the process proceeds to step P71.
Proceed to. In step P71, using the correction coefficients FTCφ, KTC and ADD obtained in the above steps,
Calculate FTCφ×(KTC+ADD+1.0) to find the warm-up acceleration correction coefficient FTC.

Correction coefficient found in steps P61 to P65 above
FTC is intake pipe pressure PM and change in intake pipe pressure
It is shown in Fig. 19 together with DPM. Referring to this figure, a predetermined value △FTCφ is added to FTCφ every time the amount of change DPM at each point exceeds the reference value REF1, and between each point, the correction coefficient FTCφ is increased by γ at each predetermined period. Subtracted.

When the coefficients FWL, FAF, and FTC in steps P11 to P13 of Fig. 5 are obtained as described above, in step P14, TP×FWL×FAF×(1+FTC)
×FTHA is calculated to obtain the corrected injection time τ, and the process returns to step P4 in FIG.

Referring to FIG. 3, voltage correction calculation is performed in step P4. That is, the voltage correction calculation routine shown in FIG. 20 is executed, and in step P81 the battery voltage BV is adjusted based on the battery voltage signal S14.
is read, and in step P82, the battery voltage shown in FIG. 21 is calculated based on the battery voltage BV.
The voltage correction coefficient τV is obtained from the map of BV and the voltage correction coefficient τV. Then, in step P83,
(τ+τV) is executed to obtain the final injection time Fτ. Then, returning to step P5 in FIG. 3 again, if it is the injection timing, in step P6, the injection signal S12 is output from the control circuit 61 to the injection valve 7, thereby driving the injection valve 7.

In addition, the intake temperature correction coefficient according to step P14 in Figure 5
FTHA is to compensate for the density of intake air, which varies depending on temperature.

In addition, in the above embodiment, the basic fuel injection time
Although TP is determined based on the engine speed and intake pipe pressure, the basic fuel injection time TP may also be determined based on the engine speed and intake air amount. Further, in the above embodiment, the warm-up increase coefficient FWL is determined by taking into account the engine speed, but it is not necessary to take the engine speed into consideration.

〔Effect of the invention〕

According to the present invention, in an internal combustion engine in which a fuel injection valve is installed upstream of an intake throttle valve, the output value at the time of startup of an intake air temperature sensor installed so as to protrude into the intake passage downstream of the intake throttle valve. an intake air temperature correction value downstream of the intake throttle valve, which is selected in accordance with the intake temperature sensor and is attenuated at a predetermined cycle after starting, regardless of the output value of the intake air temperature sensor; and a warm-up value, which is selected in accordance with the cooling water temperature of the internal combustion engine. Since the basic fuel injection amount is corrected during warm-up based on the correction value, the fuel injection amount can be appropriately increased based on the intake air temperature and cooling water temperature at that time, which correspond to the intake passage wall surface temperature at the time of startup. In addition to predicting the actual rise in wall temperature during warm-up from the intake air temperature at startup, the correction amount is attenuated accordingly. There is no need to detect the wall temperature of the intake passage, and it is possible to perform appropriate warm-up corrections at low cost, avoiding the need for multiple sensors, related new wiring, and sophisticated control circuits. This makes it possible to improve drivability in the warmed-up state even in extremely cold weather.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of an automobile internal combustion engine to which the present invention is applied, FIG. 2 is a detailed block diagram showing an example of its control circuit, and FIG. 3 is a flowchart showing an example of a fuel injection procedure. FIG. 4 is a diagram showing an example of a map for reading out the basic fuel injection time TP from the engine speed Ne and the intake pipe pressure PM.
Figure 5 is a flowchart showing an example of the procedure for calculating the corrected injection time τ, and Figure 6 is the starting temperature correction value ADD.
Flow chart showing an example of the procedure for determining
The figure is a graph showing the relationship between the intake air temperature THA at startup and the starting temperature correction value ADD, and Figure 8 is the starting temperature correction value.
A diagram showing the time decay of ADD, FIG. 9 is a flowchart showing an example of calculation processing of intake pipe pressure PM,
Fig. 10 is a diagram for explaining each procedure in Fig. 9, Fig. 11 is a flowchart showing an example of the calculation process of the warm-up increase coefficient FWL, and Fig. 12 is the engine coolant temperature THW and the warm-up correction coefficient FWLφ. FIG. 13 is a graph showing the relationship between engine speed Ne and warm-up correction coefficient KWL, FIG. 14 is a flowchart showing an example of the calculation process of feedback correction coefficient FAF, and FIG. air fuel ratio signal
A time chart showing changes over time in S7 and the correction coefficient FAF. Fig. 16 is a flowchart showing an example of the calculation process for the warm-up acceleration increase coefficient FTC. Fig. 17 shows the amount of change in intake pipe pressure DPM and the warm-up acceleration correction coefficient. △
Figure 18 is a graph showing the relationship between engine water temperature THW and warm-up acceleration correction coefficient KTC. Figure 19 is a graph showing the relationship between engine coolant temperature THW and warm-up acceleration correction coefficient KTC. Figure 19 shows the time change of intake pipe pressure PM, its change amount DPM, and correction coefficient FTCφ. The time chart shown in Figure 20 is the final fuel injection time.
FIG. 21, which is a flowchart showing an example of the calculation process of Fτ, is a graph showing the relationship between the battery voltage BV and the voltage correction coefficient τV. 7... Injection valve, 9... Intake throttle valve, 11... Intake pipe pressure sensor, 13... Intake manifold, 15... Intake temperature sensor, 17... Riser section,
19...Engine body, 27...Combustion chamber, 33...
... Water jacket, 37 ... Engine coolant temperature sensor, 41 ... O ₂ sensor, 49 ... Vehicle speed sensor, 51 ... Key switch, 53 ... Igniter, 55 ... Distributor, 57 ... Ne
Sensor, 59...G sensor, 61...Control circuit.

Claims (1)

[Claims] 1. A fuel injection valve installed upstream of an intake throttle valve of an internal combustion engine, and a relatively long intake passage that guides the air-fuel mixture injected from the fuel injection valve and mixed with intake air to the combustion chamber of the internal combustion engine. In the fuel injection amount control method for an internal combustion engine, the basic fuel injection amount is calculated based on the rotation speed and load of the internal combustion engine, and the fuel injection amount is installed so as to protrude into the intake passage downstream of the intake throttle valve. an intake air temperature correction value downstream of the intake throttle valve, which is selected according to the output value of the intake air temperature sensor at the time of starting the engine, and is attenuated at a predetermined period after the engine starts, regardless of the output value of the intake air temperature sensor; A fuel injection amount control method for an internal combustion engine, characterized in that the basic fuel injection amount is corrected during warm-up based on a warm-up correction value selected according to a cooling water temperature of the engine.