JPH0733782B2 - Fuel injection control method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel injection control method for detecting an intake pipe pressure of an engine and lean-correcting an air-fuel ratio according to the intake pipe pressure.

[Conventional technology]

Conventionally, for the purpose of improving fuel efficiency, the basic fuel injection amount is calculated based on the engine intake pipe pressure and the engine speed, and the air-fuel ratio is leaner than the theoretical air-fuel ratio when the intake pipe pressure is equal to or lower than a predetermined pressure. Therefore, there is a fuel injection control in which the basic fuel injection amount is reduced by a predetermined amount.

[Problems to be Solved by the Invention]

However, when traveling in high altitudes, the atmospheric pressure itself drops, and even in an operating state where feedback control is performed on level ground, the intake pipe pressure is reduced by the atmospheric pressure drop amount, so lean control is executed. Therefore, there is a drawback that drivability deteriorates.

An object of the present invention is to provide a fuel injection control method capable of improving drivability by appropriately performing lean control.

[Means for Solving the Problems]

In order to achieve the above object, the present invention calculates a basic fuel injection amount based on an engine intake pipe pressure and an engine speed, and when the intake pipe pressure is equal to or lower than a predetermined pressure, the air-fuel ratio is higher than the theoretical air-fuel ratio. In the fuel injection control method for reducing the basic fuel injection amount so as to be lean, the atmospheric pressure is detected, and when the atmospheric pressure is a predetermined value or less, the reduction correction amount is limited to a predetermined amount or less, That is, the basic fuel injection amount is not reduced and corrected by the predetermined amount or more.

Further, the present invention calculates the basic fuel injection amount based on the intake pipe pressure of the engine and the engine speed, determines whether the intake pipe pressure is below a predetermined pressure, and when the intake pipe pressure is below a predetermined pressure. In the fuel injection control method for reducing and correcting the basic fuel injection amount so that the air-fuel ratio becomes leaner than the stoichiometric air-fuel ratio, atmospheric pressure is detected, and when the atmospheric pressure is below a predetermined value, the intake pipe pressure is By making the determination based on a value obtained by adding a predetermined value, the reduction correction amount is limited to a predetermined amount or less so that the basic fuel injection amount is not reduced more than the predetermined amount.

[Action]

By limiting the amount of reduction correction, when the atmospheric pressure is lowered as when traveling at high altitude, the lean degree is reduced and lean control is not executed, so that drivability is improved.

In addition, by adding a constant value to the intake pipe pressure, the intake pipe pressure becomes virtually large, making it difficult to establish a lean condition.In this case as well, lean control is not executed during highland running, and drivability is reduced. improves.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a signal processing circuit for removing the pulsating component of the pressure signal detected by the intake pipe pressure sensor and at the same time improving the responsiveness during transient.

As shown in FIG. 1, this signal processing circuit includes a first low-pass filter 10 connected to a pressure sensor and a second low-pass filter 12 following the first low-pass filter 10.
And the signal V ₁ from the first low-pass filter 10 and the second
Is the signal V ₂ from the low-pass filter 12 is input (V ₁ -
V ₂ ), a subtracter 14 for calculating V ₂ ), a signal V ₃ from the subtractor 14 and a signal V ₁ from the first low-pass filter 10 are input and added, and a signal V ₄ indicating (2V ₁ −V ₂ ). And an adder 16 for outputting Then, the second low-pass filter 12 is selected to have a response delay that is approximately double that of the first low-pass filter 10.

The intake pipe pressure is a pulsating component of about 20 to 30 mmHg when the throttle valve is relatively closed, but when the engine speed is relatively low and the throttle valve is open above a certain level, that is, at about atmospheric pressure. The peak-to-peak value is 100 mmHg when the intake pipe pressure is close to, but the signal processing circuit configured in this way can improve the rising characteristics of the intake pipe pressure, and moreover, when the intake pipe pressure is close to atmospheric pressure. It is also effective in removing pulsating components.

Each of these signals V _{1 to} V ₄ has the characteristics shown in FIGS. 2 (A) and 2 (B). Here, the decay time T1 is shown until the signal V ₄ substantially converges.

A concrete example of the circuit shown in FIG. 1 is shown in FIG. In this example, three operational amplifiers OP1 to OP3, resistors R1 to R5,
It is composed of capacitors C1 to C3, and performs the same signal processing as described with reference to the above block diagram.

FIG. 4 shows a structural example of an internal combustion engine for an automobile including an electronic fuel injection control device to which the present invention is applied. The air filter 1 is connected to the slot body 5 through an inlet pipe 3. A fuel injection valve 7 is provided on the upstream side of the throttle body 5, and an intake throttle valve 9 that adjusts the intake air amount in cooperation 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 portion. Furthermore, 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 opened, and the opening of the intake throttle valve 9 is 50 A power switch 6 that is turned on only when the temperature is equal to or higher than a degree is attached in association with the intake throttle valve 9.

The slot body 5 is connected to an intake manifold 13 having a branch pipe connected to each cylinder of the engine, and the intake manifold 13 is provided with an intake air temperature sensor 15 for measuring the intake air temperature therein. A riser 17 for circulating engine cooling water to heat the air-fuel mixture is provided on the bottom wall 13a of the intake manifold 13 before branching.

Reference numeral 19 denotes a well-known conventional engine body, in which a combustion chamber 27 is formed by a piston 21, a cylinder 23, and a cylinder head 25, and a mixture gas sucked into the combustion chamber 27 through an intake valve 29 is ignited by an ignition plug 31. It is ignited by. A water jacket 33 is formed around the cylinder 23, and engine cooling water is circulated in the water jacket 33 to cool components including the cylinder 23. An engine cooling water temperature sensor 37 for measuring the engine cooling water temperature in the water jacket 33 is provided on the outer wall of the cylinder block 35.

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

Reference numeral 47 is a transmission connected to the engine body 19, and a vehicle speed sensor 49 for measuring the speed of the vehicle based on the rotation speed of the final output shaft thereof is attached. Also, 51 is a key switch,
Reference numeral 53 is an igniter, and 55 is a distributor. The distributor 55 is provided with a Ne sensor 57 that outputs an on / off signal for each predetermined crank angle θ1, and the output signal from the Ne sensor 57 causes the engine speed and a predetermined value to be determined. A G sensor 59 is provided which can know the crank angle position and which outputs an ON / OFF signal for each angle θ2 which is greater than the angle θ1, and the cylinder discrimination and the top dead center position detection are performed by the output signal. Further, 60 indicates a 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 cooling water temperature sensor 37, an O ₂ sensor 41, a vehicle speed sensor 49, a key switch 51, a Ne sensor 57, a G sensor 59 and a battery 60, respectively, and a 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, start signal S9, engine speed signal S10, cylinder discrimination signal S11
A battery voltage signal S14 is input from each sensor. Further, the control circuit 61 includes a fuel injection valve 7 and an igniter 53.
The fuel injection signal S12 and the ignition signal S13 are output based on a predetermined calculation.

As shown in FIG. 5, the control circuit 61 includes a central processing unit (CPU) 61a for controlling various devices, a read only memory (ROM) 61b in which various numerical values and programs are written in advance,
Random access memory (RAM) 61c in which numerical values and flags in the calculation process are written in a predetermined area, A / D converter (ADC) 61d that converts an analog input signal into a digital signal,
Input / output interface (I / O) 61e to which various digital signals are input and various digital signals are output, back-up memory (BU-RAM) 61f that is supplied with power from an auxiliary power supply and retains memory when the engine is stopped, and these The bus line 61g is connected to each device. The program to be described later is written in the ROM 61b in advance.

In the engine described above, fuel is injected according to the flow chart shown in FIG. Referring to FIG. 6,
In step P1, the engine speed Ne is read based on the engine speed signal S1 that is the reference position signal, and the intake pipe pressure PM is read based on the intake pipe pressure signal S4. Step P2
At the seventh, based on the rotation speed Ne and the intake pipe pressure PM,
The basic injection time TP is calculated from the map shown in the figure, and in step P3, the correction calculation process is executed according to the engine operating conditions to calculate the corrected injection time τ.

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

The injection time τ is generally obtained by the following equation.

τ = TP x FWL x FAF x FTHA x (FTC + FPO + FSE + FLEAN) ...
(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 air temperature correction coefficient FSE = post-start amplification coefficient FPO = power increase coefficient FLEAN = lean correction coefficient Therefore, each coefficient is calculated based on the τ calculation routine shown in FIG. 8 to obtain the injection time τ. Ie the procedure
In P11, the warm-up increase factor FWL is calculated, in step P12 the air-fuel ratio feedback correction factor FAF is calculated, in step P13 the transient air-fuel ratio correction factor FTC is calculated, and in step P14 the power is increased. The calculation processing of the increase coefficient FPO is executed, and in step P15 the calculation processing of the post-starting increase coefficient FSE is executed.
In step P16, the lean correction coefficient FLEAN is calculated, in step P17 the intake air temperature correction coefficient FTHA is obtained, and then in step P18,
The equation (1) is calculated and the process returns to step P4 in FIG.

In step P4, the corrected injection time τ is corrected according to the battery voltage to obtain the final injection time Fτ, and if the injection timing is determined in step P5, it corresponds to the final injection time Fτ from the fuel injection valve 7 at the timing of step P6. The injection valve 7 is opened for a period of time to discharge the fuel.

Next, each procedure P11 to P17 in FIG. 8 will be described.

The warming-up amount increase factor FWL in step P11 of FIG. 8 is, for example, the water temperature THW based on the engine cooling water temperature THW and the engine speed Ne.
Is lower and the engine speed Ne is smaller, a larger value is obtained, and the basic fuel injection time TP is increased and corrected. The air-fuel ratio feedback correction coefficient FAF in step P12 is, for example, a value smaller than 1.0 when the air-fuel ratio signal S7 from the O ₂ sensor 41 is larger than the reference value, and a value larger than 1.0 when it is smaller than the reference value. is there.

Further, the transient air-fuel ratio correction coefficient FTC in step P13 is, for example,
The change amount of the intake pipe pressure is calculated based on the intake pressure signal S4 from the intake pipe pressure sensor 11, and based on the calculated change amount, the larger the change amount is, the larger the value is obtained. To increase the correction.

Furthermore, the power increase coefficient FPO in step P14 is calculated as follows.

Referring to FIG. 9, when this program is started at a predetermined timing, the engine speed Ne is 4000r in step P51.
If it is affirmative, the data PMA read as atmospheric pressure will be read later.
Is less than 700mmHg. Atmospheric pressure PMA is 70
If it is smaller than 0 mmHg, in other words, if it is determined that the altitude is high, then the process proceeds to step P53. In step P53, it is determined whether the latest data of the intake pipe pressure PM is larger than 450 mmHg. Pressure P
If M is larger than 450 mmHg, the power increase coefficient FPO is set to 1.15 in order to increase the power in step P55. On the other hand, if the pressure PM is less than 450 mmHg, the power amount increase coefficient FPO is set to zero in step P56 so that the power amount is not increased.

If the atmospheric pressure PMA is greater than 700 mmHg in step P52, the process proceeds to step P54, and it is determined whether the pressure PM is greater than 500 mmHg. If the determination is affirmative, the power increase coefficient FPO is set to 1.15 in step P55, and if the negative determination is made, the power increase coefficient FPO is set to zero in step P56. The rotation speed Ne is 4
The coefficient FPO becomes zero even at 000 rpm or less.

Next, the procedure for obtaining the lean correction coefficient FLEAN in step P16 in FIG. 8 will be described with reference to FIG.

When the program shown in Fig. 10 is started, the procedure P21
Then, it is determined whether or not the mode condition XMODE is satisfied. This condition is satisfied when the engine is not in the starting state, is not in the post-starting increase amount, and is not in the output increasing amount, and the starting state is judged based on the start signal S9 and the engine speed signal S10. Whether or not it is determined based on the post-starting amount increase coefficient FSE stored in the predetermined storage area, and whether or not the output amount is being increased is determined based on the power increase coefficient FPO stored in the predetermined storage area. If this condition is satisfied, it is determined in step P22 whether or not the lean control execution condition is satisfied, and if it is satisfied, the process proceeds to step P23. The conditions for executing lean control are, for example, a water temperature THW of 80 ° C or higher and an intake pipe pressure PM of 550 mm.
It is satisfied when Hg or more, the intake throttle valve opening is 50 degrees or less, and the change amount of the vehicle speed SPD and the change amount of the engine speed Ne are not more than a predetermined value. These conditions are respectively the water temperature signal S
6, it is determined based on the intake pipe pressure signal S4, the power signal S3, the vehicle speed signal S8 and the engine speed signal S10.

In step P23, it is determined whether or not the data PMA as the atmospheric pressure stored in the RAM 61C in advance as described below is 700 mmHg or less, and if it is 700 mmHg or less, it is determined to be highland, and the process proceeds to step P24. It is determined whether or not the lean correction coefficient FLEAN stored in the RAM 61C is smaller than 0.8. If the lean correction coefficient FLEAN is 0.8 or less, the lean correction coefficient FLEAN is set to 0.8 in step P25, and this operation routine is ended.

That is, in lean control during highland traveling, the minimum value of the lean correction coefficient FLEAN is limited to 0.8.

If it is determined in step P23 that the atmospheric pressure PMA is not 700 mmHg or less, the process proceeds to step P26.

In step P26, the intake throttle valve 9 is operated based on the idle signal S2.
If it is affirmatively determined, the procedure proceeds to step P27, and if negatively determined, the procedure proceeds to step P28, and the lean correction coefficient FLEAN stored in the predetermined area of the RAM61C is set to 0.92, and this FLEAN calculation is performed. The process ends. In this case, lean control is executed. In step P27, the lean correction coefficient FLEAN is obtained from the map of the intake pipe pressure PM and the lean correction coefficient FLEAN having the relationship shown in FIG. 11 based on the intake pipe pressure PM and temporarily stored in the A register.

Next, in Step P29, it is judged whether or not the engine speed Ne is 2500 rpm or more, and if a positive judgment is made, in Step P30, the value of the A register is multiplied by Ne / 2500, and in Step P31, if the result is larger than 1.0. If judged, set the value of register A to 1.0 in step P32.
If it is determined that it is smaller than 1.0, the procedure skips step P32 and proceeds to step P33. In step P33, it is determined whether or not the lean correction coefficient FLEAN stored in the predetermined area of the RAM 61C is 1.0, that is, whether or not the feedback control by the air-fuel ratio signal S7 is being performed. Judge whether the vehicle speed SPD is 10km / h or more. If an affirmative decision is made, in step P35, the contents of the A register are stored in the prescribed area FLEAN of the RAM 61C, and this processing ends. Vehicle speed SPD
Is 10 Km / h or less, the rotation speed Ne is 2500 rpm or more, the condition XMODE is not satisfied, and the lean control condition is not satisfied, in step P36, 1.0 is stored in the storage area FLEAN of the RAM61C and this calculation is performed. Exit the routine.

Further, the intake air temperature correction coefficient FTHA in step P17 is performed to compensate for the density of the intake air that differs depending on the temperature, and is calculated by adding the predetermined value k to the digital value of the intake air temperature THA.

Next, the reading of the atmospheric pressure data PMA described above will be described with reference to FIG.

The program shown in Fig. 12 is started every 40ms,
In step P41, it is determined whether the power signal S3 is on (high level). In other words, it is determined from the power signal S3 whether or not the intake throttle valve 9 is open at 50 degrees or more. If the intake throttle valve opening is 50 degrees or less, the process proceeds to step P42, and the counter COU is reset to zero. If the power signal S3 is on, the process proceeds to step P43, and it is determined whether the engine speed Ne is 2000 rpm or less. If a negative decision is made, the counter COU is reset in step P42.

If the intake throttle valve 9 is open at 50 degrees or more and the engine speed Ne is 2000 rpm or less, the process proceeds to step P44. Step P44
Then, the counter COU is incremented by +1. And step P
At 45, it is determined whether or not the count value of the counter COU is equal to 250, and if a positive determination is made, at step P46, the latest intake pipe pressure data is stored in the predetermined area RMA of the RAM 61C so as to be regarded as atmospheric pressure. The lever calculation routine ends.

As described above, in the present embodiment including the first and second inventions, the intake throttle valve opening is 50 degrees or more, and the engine speed Ne is 2000.
When the engine operating state below rpm is continuously maintained for 1 second, the latest intake pipe pressure data is regarded as the atmospheric pressure PMA, and the atmospheric pressure PMA is 700 mmHg when the power increase coefficient FPO and the lean correction coefficient FLEAN are calculated. If it is smaller, it is judged that it is highland, and the judgment level of whether to increase the power is changed from 500 mmHg to 450 mmHg, and the lean correction coefficient FLEA
The minimum value of N was limited to 0.8.

Therefore, there is no fear that the output will decrease during high-altitude running and that the catalyst will be overheated and its durability will be impaired.

An embodiment including the third and fourth inventions will be described with reference to FIGS. 13 and 14.

When the FPO calculation program shown in Fig. 13 is started, the procedure P
At 61, determine whether the engine speed Ne is 4000 rpm or more,
Data PMA read as atmospheric pressure in step P62 is 700 m
Judge whether it is less than mHg. If these steps are affirmatively determined and the procedure proceeds to Step P63, in Step P63, the data PMA is subtracted from the value 760 mmHg indicating the atmospheric pressure on the flat ground, and the result is added to the intake tube pressure PM to add a new intake tube pressure PM. And Next, in step P64, the intake pipe pressure PM is set to 500
If it is determined whether it is larger than mmHg or not, the power increase coefficient FPO is set to 1.15. When a negative determination is made in steps P61, P62 or P64, the power amount increase coefficient FPO is set to zero in step P66.

When the FLEAN calculation program shown in FIG. 14 is started, it is determined in step P71 whether or not the XMODE condition is satisfied. If the result is affirmative, the process proceeds to step P72, in which it is determined whether the atmospheric pressure PMA is larger than 700 mmHg. To judge. If PMA is less than 700 mmHg, proceed to step P73. In procedure P73, the data PMA is subtracted from the value 760 mmHg indicating the atmospheric pressure on the flat ground, and the result is added to the intake pipe pressure PM to obtain a new intake pipe pressure PM.
In step P74, similarly to step P22 shown in FIG. 10, it is determined whether or not the lean control condition is satisfied, and if a positive determination is made, the process proceeds to step P75 to determine whether or not the idle switch 4 is off. To judge. For subsequent steps,
Since it is similar to steps P27 to P36 in FIG.

Except for the power increase coefficient FPO and the lean correction coefficient FLEAN, it is the same as in the first embodiment described above.

As described above, in the embodiments including the third and fourth inventions, if the pressure PMA read as the atmospheric pressure is smaller than 700 mmHg, the atmospheric pressure data PMA is subtracted from the value 760 mmHg indicating the atmospheric pressure on the flatland, and Altitude compensation was performed by adding the result to the intake pipe pressure PM. It should be noted that the value of 760 mmHg, which indicates the atmospheric pressure on a flat ground, varies depending on the engine specifications, and may be, for example, the value of 740 mmHg.

Note that, in step P45 of FIG. 12, the engine speed Ne
Is 2000 rpm or less and the state in which the intake throttle valve opening is 50 degrees or more is judged for 1 second or longer. This time is explained in FIGS. 1 to 3. It is a value larger than the decay time T 1 of the output signal V ₄ in the signal processing circuit.

〔The invention's effect〕

As described above, according to the present invention, when the atmospheric pressure is reduced such as when traveling at high altitude, execution of lean control is avoided and proper engine control is performed, so that drivability is improved. You can

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a circuit for processing a signal from an intake pipe pressure sensor, FIGS. 2 (A) and 2 (B) are time charts showing signal waveforms of respective parts of the processing circuit, and FIG. FIG. 4 is a circuit diagram showing a specific example of FIG. 1, FIG. 4 is a configuration diagram showing an example of an internal combustion engine for an automobile to which the present invention is applied, FIG. 5 is a detailed block diagram showing an example of its control circuit, and FIG. 6 is a fuel. A flow chart showing an example of the injection procedure, FIG. 7 is a diagram showing an example of a map for reading the basic fuel injection time TP from the engine speed Ne and the intake pipe pressure PM, and FIG. 8 is a corrected injection time. FIG. 9 is a flow chart showing an example of the procedure for obtaining τ, FIG. 9 is a flow chart showing an example of the calculation processing of the power increase coefficient FPO, and FIG. 10 is a flow chart showing an example of the calculation processing of the lean correction coefficient FLEAN, FIG. Is the relationship between the intake pipe pressure PM and the lean correction coefficient FLEAN. To graph, FIG. 12 shows an example of a procedure for reading the data as an atmospheric pressure flow chart, the 13 flow chart diagram showing another example of the calculation of the power correction coefficient FPO, Fig. 14 Lean correction coefficient FL
It is a flow chart which shows the other example of the arithmetic processing of EAN. 7 ... Injection valve, 9 ... Intake throttle valve, 11 ... Intake pipe pressure sensor, 13 ... Intake manifold, 15 ... Intake temperature sensor, 17 ... Riser part, 19 ... Engine body, 27 ... Combustion Room, 33 …… Water jacket, 37 …… Engine cooling water 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.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-58-48746 (JP, A) JP-A-58-65950 (JP, A) JP-A-58-75313 (JP, A) JP-B-53- 13739 (JP, B2)

Claims (2)

[Claims] 1. A basic fuel injection amount is calculated based on an engine intake pipe pressure and an engine speed, and the air-fuel ratio becomes leaner than a theoretical air-fuel ratio when the intake pipe pressure is equal to or lower than a predetermined pressure. In a fuel injection control method for reducing the basic fuel injection amount, the atmospheric pressure is detected, and when the atmospheric pressure is a predetermined value or less, the reduction correction amount is limited to a predetermined amount or less so that the basic fuel injection amount is A fuel injection control method characterized in that a reduction correction is not performed by a predetermined amount or more. 2. A basic fuel injection amount is calculated based on an engine intake pipe pressure and an engine speed, and it is determined whether or not the intake pipe pressure is below a predetermined pressure. When the intake pipe pressure is below a predetermined pressure, In a fuel injection control method for reducing and correcting the basic fuel injection amount so that the air-fuel ratio becomes leaner than the theoretical air-fuel ratio, atmospheric pressure is detected, and when the atmospheric pressure is below a predetermined value, the intake pipe pressure is set to a predetermined value. Fuel injection characterized by limiting the reduction correction amount to a predetermined amount or less by making the determination based on a value obtained by adding the values so that the basic fuel injection amount is not reduced and corrected by the predetermined amount or more. Control method.