JPH01315635A - Fuel injection quantity control of internal combustion engine - Google Patents

Abstract

PURPOSE:To improve the quantitative precision for fuel injection in an equipment which controls fuel injection based on both the quantity of intake air forecasted ahead by the specified period and engine speed by compensating the forecasted quantity of intake air using the atmospheric pressure or the pressure at the upper side of a throttle valve. CONSTITUTION:During operation of an internal combustion engine, various output signals from a throttle valve opening sensor 10 and a revolution angle sensor 48 are sent to a control circuit 44 to decide the intake pipe pressure in the normal operation state on the bases of the throttle valve opening and the engine speed. Said pressure in the intake pipe is compensated with a compensative valve based on variation in pressure in the intake pipe and using both the compensated intake pipe pressure and the engine speed, a weighing function (n) is obtained. An initial value is calculated from the actual intake pipe pressure, the function (n) and the compensated intake pipe pressure and a forecasted pressure in the intake pipe is computed from this initial value, the function (n) and the actual intake pipe pressure. Using this forecasted value and the engine speed, the quantity of fuel to be injected to controlled.

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, and particularly to a fuel injection amount control method for an internal combustion engine, in which the fuel injection amount is controlled based on a throttle opening degree and an engine rotation speed. This invention relates to an injection amount control method.

[Conventional technology]

Conventionally, the amount of air passing upstream of the throttle valve and the engine speed, or the intake pipe absolute pressure downstream of the throttle valve (
BACKGROUND ART Internal combustion engines are known in which the amount of fuel injection is controlled based on intake pipe pressure (hereinafter referred to as intake pipe pressure) and engine rotational speed. The above physical quantities of air amount and intake pipe pressure both correspond to the amount of intake air taken into the engine combustion chamber, and in the above internal combustion engine, the intake air per engine rotation is determined from these physical quantities and the engine rotation speed. In addition to calculating the air amount, the basic fuel injection time is calculated by considering the air-fuel ratio based on the intake air amount per engine revolution, and the fuel injection time is calculated by correcting this basic fuel injection time with intake air temperature, engine cooling water temperature, etc. The fuel injection amount is controlled by opening the fuel injection valve for a time corresponding to this fuel injection time.

When controlling the fuel injection amount based on intake pipe pressure and engine speed, a diaphragm pressure sensor is installed in the intake pipe downstream of the throttle valve, and a time constant is set to remove engine pulsation components. By processing the pressure sensor output through a filter of about 3 to 5 m5ec, the intake pipe pressure is detected and the intake air amount is indirectly detected. However, because there is a response delay due to the diaphragm of the pressure sensor and a response delay due to the time constant of the filter, during transient operation such as during acceleration/deceleration, the detected change in intake pipe pressure may differ from the actual change in intake pipe pressure. There will be a time delay. For this reason, when accelerating, the throttle valve is suddenly closed and the actual intake pipe pressure suddenly rises, but there is a time delay in the detected intake pipe pressure, and the intake pipe pressure is smaller than the actual intake pipe pressure. Since the basic fuel injection time is calculated based on pressure, the air-fuel ratio becomes over-lean, deteriorating acceleration response and deteriorating exhaust emissions. On the other hand, during deceleration, the throttle valve is suddenly closed and the intake pipe pressure drops dramatically, so the basic fuel injection time is calculated using an intake pipe pressure that is larger than the actual intake pipe pressure. The air-fuel ratio becomes overrich, resulting in poor drivability and poor exhaust emissions. In order to prevent over-rich and over-lean air-fuel ratios, various corrections are made such as increasing acceleration and decreasing deceleration, but during transients there is a time delay in the detected intake pipe pressure, so It is impossible to completely control the air-fuel ratio to the target air-fuel ratio.

In addition, when controlling the fuel injection amount based on the air amount and engine rotation speed, a flow sensor such as an air flow meter or Karman vortex flowmeter is installed upstream of the throttle valve to detect the air amount, which allows direct intake. The amount of air is detected, but since the flow rate sensor is installed upstream of the throttle valve, there is a delay in response between changes in the flow rate sensor output and changes in the actual intake air amount, resulting in the same problem as above. Occur.

For this reason, the throttle opening is used as a physical quantity with no time delay with respect to the actual intake air amount, and the fuel injection amount is controlled based on the throttle opening and the engine rotational speed. That is, JP-A-59-28031, JP-A-59-196949 and JP-A-60
Japanese Patent Laid-open No. 122237 discloses controlling the fuel injection amount by calculating the basic fuel injection time based on the throttle opening degree and the engine speed, and Japanese Patent Application Laid-Open No. 1983-39948 discloses that the basic fuel injection time is calculated based on the throttle opening degree and the engine speed. It is disclosed that the intake pipe pressure is calculated based on the engine rotation speed and the engine rotation speed, and the basic fuel injection time is calculated using the calculated intake pipe pressure and the engine rotation speed to control the fuel injection amount. The above throttle opening is determined by the throttle opening sensor, which is composed of a contact fixed to the rotating shaft of the throttle valve and a variable resistor connected to a power source at one end and grounded at the other end. It is detected by a voltage proportional to the temperature. However, the throttle valve is usually located upstream, away from the engine combustion chamber, and there is a time delay before the air passing through the throttle valve reaches the engine combustion chamber. Because of the volume in between, the phase of the throttle opening advances with respect to changes in the actual intake air amount. For this reason,
The intake pipe pressure P (TA, NE) determined by the throttle opening and the engine rotational speed has a value that is in phase with the actual intake pipe pressure P, as shown in FIG. Note that PM is the intake pipe pressure obtained from the pressure sensor.

In addition, as shown in Fig. 6, the basic fuel injection time TP (TA, NE
) is larger than the required fuel injection amount because the change in throttle opening is ahead of the change in actual intake air amount. Therefore, if the fuel injection amount is controlled based on the throttle opening and engine speed, even if the throttle opening sensor is normal, the fuel injection amount will exceed the required value during acceleration and the air-fuel ratio will become overrich. During deceleration, the fuel injection amount becomes less than the required value and the air-fuel ratio becomes over-lean. Further, even when the acceleration increase correction is performed, the increase value becomes as shown by diagonal lines in FIG. 6, and the above-mentioned phase advance cannot be corrected.

Incidentally, the amount of air supplied to the engine combustion chamber is determined at the end of intake, that is, when the intake valve is closed. However, a predetermined time is required to calculate the fuel injection time, a predetermined flight time is required for the fuel injected from the fuel injection valve to reach the combustion chamber, and the amount of air supplied to the combustion chamber If the fuel injection amount is calculated when the amount of air is determined, there will be a time delay, so conventionally, the basic fuel injection time is calculated using the intake pipe pressure before the amount of air supplied to the combustion chamber is determined. For this reason, the amount of fuel that matches the amount of air actually taken into the combustion chamber is no longer injected, and during acceleration, the amount of fuel injection is controlled by an intake pipe pressure that is smaller than the intake pipe pressure that determines the amount of intake air. Therefore, the air-fuel ratio becomes lean, and during deceleration, the fuel injection amount is controlled by the intake pipe pressure that is larger than the intake pipe pressure at which the intake air amount is determined, so the air-fuel ratio becomes rich.

For this reason, the present applicant calculates the intake pipe pressure PMTA in a steady state based on the throttle opening degree and engine speed without delay in response to the actual intake pipe pressure, and calculates the intake pipe pressure PMTA in the steady state. The time point at which the current intake pipe pressure PMCRT with no phase lead or phase lag is calculated by correcting the response delay during transients, and the amount of air taken into the engine is determined based on the calculated intake pipe pressure. A method has already been proposed in which the intake pipe pressure PMFWD is predicted at the engine speed and the fuel injection amount is controlled based on this predicted value and the engine speed (Japanese Patent Application No. 51056/1982).

[Problem to be solved by the invention]

However, in the method of controlling the fuel injection amount using the throttle opening as a parameter, which has already been proposed by the applicant, if the atmospheric pressure changes, the air density changes and combustion occurs even if the throttle opening is constant. Since the amount of air supplied to the chamber changes, there is a problem in that a discrepancy occurs between the engine request value and the calculated fuel injection amount, which may cause disturbances in emissions. Furthermore, when applied to an engine equipped with a supercharger, the same problem as above occurs. In order to solve these problems, it is possible to actually measure the intake pipe pressure and sequentially correct the current intake pipe pressure PMCRT calculated from this measured value, but the deviation due to atmospheric pressure is larger as the load is higher. Therefore, there is a problem in that the accuracy of predicted values during transient times deteriorates. That is, to explain with reference to FIG. 7, taking as an example the point in time when the throttle valve is fully open during full-open acceleration, the deviation WJa of the intake pipe pressure PMTA in a steady state, that is, the true deviation amount of the atmospheric pressure, is as described above. Since it is larger than the deviation amount (correction value) b resulting from the sequential correction of , the intake pipe pressure PMTA corrected using the deviation amount is smaller than the true value. Therefore, the predicted value PM obtained using the corrected intake pipe pressure PMTA
FWD becomes smaller than the true predicted value, resulting in acceleration lean.

In addition, in engines equipped with a supercharger, a blower for supercharging is provided upstream of the throttle valve, so the pressure upstream of the throttle valve fluctuates greatly depending on the operating conditions.
The intake pipe pressures PMTA and PMCRT change as shown in FIG. Even in an engine equipped with this supercharger, a deviation similar to that shown in FIG. 7 occurs.

The present invention has been made to solve the above problems, and is an internal combustion engine capable of controlling the fuel injection amount by determining the intake pipe pressure with high accuracy by correcting atmospheric pressure and boost pressure. The purpose of the present invention is to provide a fuel injection amount control method.

[Means to solve the problem]

In order to achieve the above object, the present invention calculates the current amount of intake air based on the throttle opening degree and engine rotational speed, and calculates the intake air amount for a predetermined period of time after the calculation time based on the obtained current amount of intake air. In the fuel injection control method for internal combustion engines, which calculates the predicted value of the amount and controls the fuel injection amount based on the calculated predicted value and engine rotational speed, atmospheric pressure or the pressure on the upstream side of the throttle valve is detected. The predicted value of the intake air amount is corrected based on the atmospheric pressure or the pressure upstream of the throttle valve.

[Effect]

According to the present invention, the current intake air amount is calculated based on the throttle opening degree and the engine rotation speed.

Then, a predicted value of the intake air amount for a predetermined period of time after the calculation time is calculated based on the calculated current intake air amount.

In addition, atmospheric pressure or the pressure on the upstream side of the throttle valve is detected, and the predicted value of the intake air amount calculated above is determined based on the detected atmospheric pressure in the case of a naturally aspirated engine, or depending on the detected atmospheric pressure in the case of a supercharged engine. This corrected prediction is corrected by the detected pressure upstream of the throttle valve (corresponding to atmospheric pressure when the turbocharger is not operating and to boost pressure when the turbocharger is operating). The fuel injection amount is controlled based on the value and the engine speed. In this way, the predicted value of the intake air amount is corrected using the detected atmospheric pressure or the pressure upstream of the throttle valve, so there may be errors in the calculated predicted value due to atmospheric pressure fluctuations or turbocharger operation. is also corrected to the true value, thereby preventing disturbances in exhaust emissions.

The present invention can employ the following method when calculating the current intake air amount based on the throttle opening degree and engine rotation speed.

The first method is to calculate the intake pipe pressure using the elapsed time from the throttle opening change point as a variable based on the throttle opening and engine speed, and use this intake pipe pressure as the current intake pipe pressure. It is.

The principle of the first method will be explained below. As shown in Fig. 2, considering the intake system from the throttle valve Th through the surge tank S to the intake valve of the engine E, the air pressure in the intake system (intake pipe absolute pressure) is P [mmflgabs, co, The volume of the intake system is ■ [I2], the weight of the air in the intake system is Q [g], and the absolute temperature of the air in the intake system is T [
' K], the atmospheric pressure is Pc [mmHgabs, ], and the air weight per unit time taken into the combustion chamber of engine E from the intake system is ΔQ+ [g/5ecl,
The weight of air passed through the throttle valve Th and sucked into the intake system per unit time is ΔQ2 [g/sec],
The weight of air in the intake system within a minute time ΔL is (ΔQ2−ΔQ
, )・Δ is changed, and at this time the air pressure in the intake system becomes Δ
When the Boyle-Charles law is applied to the air in the intake system, assuming that P has changed, the result is shown in (1) 2 below.

(P+Δp)v= (Q+(ΔQ2−ΔQ,)Δt) RT...
(1) However, R is a gas constant.

On the other hand, since PV=Q-R-T, if the above equation (1) is modified, the following equation (2) is obtained.

Δj V Here, if the flow coefficient is ψ and the opening area of the throttle valve (throttle opening) is A, the air weight ΔQ2 per unit time passing through the throttle valve is expressed by the following equation (3), and the stroke volume Let v8 be the engine rotational speed, NE [rpm] be the engine rotational speed, and η be the suction efficiency.The air weight ΔQ1 per unit time taken into the combustion chamber of the engine is expressed by the following equation (4).

ΔQ, = ψ・AjTzτ: Bottom...(3) Above (3)
, by substituting equation (4) into equation (2), the following equation (5) is obtained.

Here, if we take the limit of ΔL→0, we get becomes.

Now, considering the response near the pressure PG (≠PC), assuming that the pressure changes from Po to PO + P, the above (6)
By substituting po + p (where P is a small value) in place of P in the equation, the following equation (7) is obtained.

...(7) ...(8) Therefore, the above equation (7) becomes the following equation (9).

2 V 60 ...(9) here, 2■60 Then, the above equation (9) becomes as follows.

t If the above 0 equation is transformed into the following equation 03) and both sides are integrated, and the integral constant is C, the following side equation is obtained.

■ −−1og (−a P+b) = M
+ C-(14) Here, when L=0, the initial value of P is Po
Therefore, from the above formula 04, the integral constant C is as follows.

C=−−1og(−aPo+b) ・”(15) P is calculated from the above side equation and the equation 05) as follows.

a a However, e is the base of natural logarithm.

Therefore, by measuring the opening area A of the throttle valve, that is, the throttle opening TA, the engine speed NE, and the elapsed time t from the time when the throttle opening changes, and substituting it into the above equation 00, the current intake pipe pressure P (the following PMCRT) can be obtained.

Then, a predicted value for a predetermined time ahead is calculated based on the current intake pipe pressure P obtained in this way, and this predicted value is corrected using the detected atmospheric pressure or the pressure on the upstream side of the throttle valve, and the corrected predicted value is Based on and the engine rotational speed NE,
Find the basic fuel injection time TP, and calculate the basic fuel injection time T.
The fuel injection time is determined by correcting P according to the intake air temperature, engine cooling water temperature, etc., and by opening the fuel injection valve for a time corresponding to this fuel injection time, the amount of fuel required by the engine can be injected. can.

By the way, if the current intake pipe pressure P of the above equation 06) is expressed in a graph, it will be as shown in Fig. 3, and if 1=0, P=Po
, t→ω in the limit (steady state) is the output of the first-order lag element where P=b/a (intake pipe pressure PMTA in steady state). Therefore, throttle opening TA and engine rotation speed NE
The intake pipe pressure PMTA in the steady state is calculated based on The intake pipe pressure may also be calculated.

However, S is a Laplace transform operator and T is a time constant.

That is, in the first method, the intake pipe pressure in a steady state is calculated based on the throttle opening degree and the engine rotation speed,
The intake pipe pressure (current intake pipe pressure) with the elapsed time as a variable may be calculated by processing the calculated intake pipe pressure in a steady state using a first-order lag element.

In addition, the second method calculates the intake pipe pressure in a steady state at a predetermined period based on the throttle opening degree and the engine rotational speed, and calculates the intake pipe pressure in a steady state based on the throttle opening degree and the engine rotational speed, and calculates the intake pipe pressure in a steady state based on the throttle opening degree and the engine rotation speed, and A coefficient related to the weight is calculated, and the weight of the weighted average value calculated in the past is increased, and a current weighted average value is obtained using the weighted average value calculated in the past, the intake pipe pressure in the steady state, and the coefficient related to the weight. is calculated, and this current weighted average value is used as the current intake pipe pressure.

Next, the principle of this method will be explained. A block diagram of the first-order delay element is shown in Figure 4, and the human power is expressed as x(t
), the output is y(t), and the time constant is T, the input-output relationship in FIG. 4 is expressed by the following equation.

...Q■ Here, if L2 is the current calculation timing and tl is the past calculation timing, the following equation (21) is obtained (tx
t+) ・(x(muz)
y (t+)I+y (t+)= y (tz)
...(21) In the above (21), x (tz) is the intake pipe pressure in steady state JPMTA, y (tz) is the current intake pipe pressure PMSM+, y(t+) is the past intake pipe pressure If PMS Mi-,, tzL+(-ΔL) is the calculation period, then ΔL-(PMTA-PMSMi,,I)+PMSM,-,=PMSM,...(22),
When T/ΔL=n, the following equation (23) is obtained.

...(23) In other words, the above equation (23) is based on the past intake pipe pressure PM
It is shown that the current intake pipe pressure PMSM can be calculated by calculating the weighted average with the weight of S M , -1 set to n-1 and the weight of the intake pipe pressure PMTA in the steady state set to 1. There is. Further, the coefficient n regarding the weight is determined by the ratio of the time constant T and the calculation period ΔL.

Therefore, the intake pipe pressure PMTA in a steady state is calculated at a predetermined period ΔL based on the throttle opening degree and the engine rotational speed, and a coefficient related to weighting is calculated using a time constant T regarding changes in intake pipe pressure during a transient period and a predetermined period Δt. n is calculated, and the weighted average value PMSMi-, calculated in the past is increased, and the weighted average value PMSMi-, calculated in the past, the intake pipe pressure PMTA in the steady state, and the coefficient n regarding the weight are calculated as above. (23
), the current intake pipe pressure can be determined by calculating the weighted average value PMSM according to the equation.

Note that, as understood from the above equation 0ω, 06), the time constant T=l/a becomes smaller as the engine rotational speed NE becomes larger, and becomes smaller as the throttle opening TA becomes larger.

In this way, the time constant is expressed by a function with the throttle opening TA (!l: engine speed NE as a variable. Therefore, if the calculation period Δt is constant, the coefficient n related to the weight is the throttle opening TA, !l: It can be determined by a function with the engine rotational speed NE as a variable.The throttle opening degree TA
Intake pipe pressure PMT in steady state with and engine speed NE
Since A is uniquely determined, the intake pipe pressure PMTA in a steady state can be used instead of the throttle opening TA and the engine rotation speed NE.
The weighting coefficient n may be determined according to the engine speed NE and the engine speed NE.

On the other hand, in the above equation (23), assuming that the throttle opening degree TA and the engine rotational speed NE do not change, the predetermined period from the weighted average value calculation until the intake air amount is determined, that is, from the weighted average value calculation to the predetermined The intake pipe pressure PMTA in the steady state is constant up to a certain time. Therefore, the above (
By repeatedly calculating the weighted average value of equation 23), it is possible to predict the actual intake pipe pressure when the intake air amount is determined.

In this case, if an error occurs in the past intake pipe pressure PMSM=-+, an error will also occur in the predicted value, so in this embodiment, the intake pipe pressure in the steady state is The number of calculations is obtained by dividing the time until the air amount is determined by the calculation period Δ, the intake pipe pressure is detected by the pressure sensor, and the detected intake pipe pressure is used as the initial value and the number of calculations described above (23 ) By repeating the calculation of the weighted average of the formula, the weighted average value at the time when the amount of air taken into the engine is determined, that is, the intake pipe pressure at the time when the amount of air taken into the engine is determined, is predicted. The predicted value is corrected using the detected atmospheric pressure or the pressure upstream of the throttle valve, and then the corrected predicted value is used to control the fuel injection amount.

Note that the above assumes that the throttle opening and engine rotational speed do not change from the time the fuel injection time is calculated until the amount of air taken into the engine is determined, but the throttle opening and engine rotational speed may change. In this case, the differential value of the throttle opening and/or the differential value of the engine rotational speed at the time of calculating the fuel injection time is used to predict the throttle opening and/or the engine rotational speed at the time of the next fuel injection time calculation. hand,
If you predict the intake pipe pressure in a steady state when the intake air amount is determined, and calculate the weighted average value as described above to predict the actual intake pipe pressure, it will be possible to predict the actual intake pipe pressure when the throttle opening or engine speed changes. The accuracy of the predicted value of the actual intake pipe pressure is further improved.

〔Effect of the invention〕

As explained above, according to the present invention, the calculated predicted value of the intake air amount is corrected by the detected atmospheric pressure or the pressure on the upstream side of the throttle valve, so that the error in the predicted value from the true value is small. This results in the effect that disturbances in exhaust emissions can be prevented.

〔Example〕

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

FIG. 9 is a schematic diagram of a naturally aspirated internal combustion engine equipped with a fuel injection amount control device to which the present invention is applicable.

A throttle valve 8 is located downstream of the air cleaner (not shown).
is located. A throttle opening sensor lO for detecting the opening of the throttle valve 8 is attached to the throttle valve 8. The throttle opening sensor 10 is the 10th
As shown in the equivalent circuit in the figure, the throttle valve 8 is composed of a contact 10B fixed to the rotating shaft of the throttle valve 8 and a variable resistor 10A connected to a power source at one end and grounded at the other end. As the opening degree of contact 10B changes,
The contact state between the variable resistor 10A and the variable resistor 10A changes, and a voltage corresponding to the opening degree of the throttle valve 8 is obtained from the contact lOB. Also, provided within the throttle opening sensor 10 is an idle switch 11 that is turned on when the throttle valve is fully closed (idle). Throttle valve 8
A temperature sensor I4 composed of a thermistor for detecting the temperature of intake air is attached to the upstream side of the intake pipe wall. A surge tank 12 is arranged downstream of the throttle valve 8. A diaphragm type pressure sensor 6 is attached to this surge tank 12 . The output signal from this pressure sensor 6 has a small time constant (for example, 3 to 5 m5ec) to remove the pulsating component of the intake pipe pressure.
The filter 7 is composed of a CR filter or the like with good responsiveness.
(See FIG. 11). Further, a bypass passage 15 is provided to bypass the throttle valve and communicate the upstream side of the throttle valve with the downstream side of the throttle valve. An ISC valve 16 is attached to the bypass passage 15, and is composed of a pulse smoke 16A having a four-pole stator and a valve body 16B whose opening degree is controlled by the pulse motor.

The surge tank 12 is communicated with a combustion chamber 25 of the engine body 20 via an intake manifold 18, an intake boat 22, and an intake valve 23. A fuel injection valve 24 is attached to this intake manifold 24 so as to correspond to each cylinder, and is configured to be able to inject fuel to each cylinder independently, to each group of cylinders, or to all cylinders simultaneously. .

The combustion chamber 25 is communicated with a catalyst device (not shown) filled with a three-way catalyst via an exhaust valve 27, an exhaust boat 26, and an exhaust manifold 28. A 0□ sensor 30 is attached to the exhaust manifold 28 for detecting the residual oxygen concentration in the exhaust gas and outputting a signal that is inverted at a value corresponding to the stoichiometric air-fuel ratio.

A cooling water temperature sensor 34 made of a thermistor or the like is attached to the cylinder block 32 so as to protrude into the water jacket and detects the engine cooling water temperature representative of the engine temperature. A spark plug 38 is attached to the cylinder head 36 so as to protrude into each combustion chamber 25 . The spark plug 38 is connected to a control circuit 44 composed of a microcomputer or the like via a distributor 40 and an igniter 42 equipped with an ignition coil. Attached to the distributor 40 are a cylinder discrimination sensor 46 and a rotation angle sensor 48, each of which includes a signal rotor fixed to the distributor shaft and a pickup fixed to the distributor housing.

The cylinder discrimination sensor 46 outputs a cylinder discrimination signal, for example, every 720'CA, and the rotation angle sensor 48 outputs a cylinder discrimination signal, for example, every 720°C.
A rotation angle signal is output for each A. Then, the engine rotation speed can be calculated from the period of this rotation angle signal.

A control circuit 44 composed of a microcomputer etc.
As shown in FIG. 11, a microprocessing unit (MPU) 60, a read-only memory (ROM)
62, random access memory (RAM) 64, backup RAM (BU-RAM) 66, input/output capotro 8, input port door 0, output port door 2.74.76, and data bus, control bus, etc. that connect these. Equipped with bus 75. An analog-to-digital (A/D) converter 78 and a multiplexer 80 are connected in sequence to the input and output ports.
0 is connected to the intake temperature sensor 14 via a buffer 82, and is also connected to the water temperature sensor 34 and the throttle opening sensor IO via buffers 84 and 85, respectively. Further, the pressure sensor 6 is connected to the multiplexer 80 via a buffer 83 and an RC filter 7 composed of a resistor R and a capacitor C. And input/output capotro 8 is A/D conversion 2S78
and the multiplexer 80, and are connected to the intake air temperature sensor 14 output, the pressure sensor 6 output, and the water temperature sensor 3 which are input via the RC filter 7 according to the control signal from the MPU.
4 outputs and the throttle opening sensor 10 output are controlled to be A/D converted sequentially at a predetermined period.

The 02 sensor 30 is connected to the input port door 0 via a comparator 88 and a buffer 86, and the cylinder discrimination sensor 46 and the rotation angle sensor 48 are also connected via a waveform shaping circuit 90. A switch 11 is connected. The output port door 2 is connected to the igniter 42 via a drive circuit 92, the output port door 4 is connected to the fuel injection valve 24 via a drive circuit 94, and the output port door 6 is connected to the ISC via a drive amount path 96. It is connected to the pulp pulse motor 16A.

Next, an embodiment in which the second method described above is applied to the internal combustion engine will be described. The ROM 62 contains the control routine program described below, a map of the intake pipe pressure PMTA in a steady state determined by the throttle opening TA and the engine rotational speed NE shown in FIG. 12, and the engine engine shown in FIG. Rotational speed NE and intake pipe pressure PMT in steady state
A map of the coefficient n regarding the weight determined by A (or throttle opening TA), and a map of the basic fuel injection time TP determined by the predicted intake pipe pressure PMFWD and engine rotational speed NE shown in FIG. is stored in advance. Intake pipe pressure PMTA in steady state shown in Figure 12
In this map, the throttle opening TA and engine speed NE are set under atmospheric pressure, the intake pipe pressure corresponding to the set throttle opening TA and engine speed NE is measured, and the intake pipe pressure is stabilized. It is created by using the value of The map of the coefficient in regarding the weight shown in FIG. 13 is obtained by measuring the specific @T at the time of the intake pipe pressure response (individual response) when the throttle valve is opened in a stepwise manner.
By calculating T/Δt (:n) from this measured value and the execution period Δt sec of the calculation routine in correspondence with the engine rotation speed NE and the actual intake pipe pressure PMT A (or throttle opening TA). Created. The basic fuel injection time TPO map in FIG.
It is created by measuring the basic fuel injection time TP.

Next, correction of predicted values in this embodiment will be explained.

In an engine equipped with the bypass passage explained in Fig. 9, there is a possibility that a deviation in intake pipe pressure will occur due to the flow rate control of the bypass passage (larger as the load becomes lighter) and deviation due to atmospheric pressure (larger as the load becomes higher). There is. Therefore, in this embodiment, the error due to the influence of the amount of air flowing through the bypass path and the error due to the decrease in atmospheric pressure are corrected. First, 8 m5e is executed every predetermined time (for example, 8 m5ec) according to the embodiment of the present invention.
The c routine will be explained based on FIG. Step 1
At 50, the engine rotational speed NE, the A/D converted throttle opening TA, and the intake pipe pressure PM inputted via the RC filter and then A/D converted are taken in. In addition,
A/D conversion of the throttle opening and intake pipe pressure is performed by an interrupt routine that is executed every predetermined time (for example, 8 m5ec), not shown. Next step 15
2, the intake pipe pressure PM in the steady state is determined from the map shown in FIG. 12 from the engine rotational speed NE and the throttle opening TA.
Calculate TA. In the next step 154, a weight-related coefficient n is calculated from a map shown in FIG. 13 from the engine rotational speed NE and the steady state intake pipe pressure P MTA calculated in step 152.

In the next step 156, the current intake pipe pressure PMCRT is calculated according to the following equation.

PMCRT 4-PMCRT+-(PMTA-Plvf
CRT) (24) Since the intake pipe pressure PMCRT calculated by the above equation (24) may include an error due to the amount of air flowing through the bypass passage, the pressure sensor is Intake pipe pressure PMCR from detected intake pipe pressure PM
A correction value K is calculated by subtracting T.

FIG. 1 shows a routine for calculating the fuel injection time TAU. In step 100, the engine rotational speed NE,
Take in the throttle opening TA, intake pipe pressure PM, and atmospheric pressure. Here, the output of the pressure sensor 6 at the start of startup or the output of the pressure sensor 6 when the throttle valve is fully opened can be used as a value indicating the atmospheric pressure, but an atmospheric pressure sensor may also be attached to detect the atmospheric pressure. . In the next step 101, the intake pipe pressure PMTA in the steady state is determined in the same manner as above based on the engine rotational speed NE and the throttle opening TA. Since this intake pipe pressure PMTA may include an error due to the amount of air flowing through the bypass passage and an error due to a decrease in atmospheric pressure, it is corrected according to the following formula using the correction value K calculated in step 158. I do.

In the next step 104, the engine rotation speed NE and (25)
Using the steady state intake pipe pressure PMTAI corrected by the formula, the weighting factor n is determined in the same manner as above.

In the next step 106, the time T from the current time to the predicted intake pipe pressure time is determined. m5ec is the calculation cycle Δ of this routine
By dividing by L (for example, 8m5ec), the number of calculations from the current time to the intake pipe pressure prediction time N = T, /Δ
Calculate L. This predicted time Tomsec can be the time from the current time until the intake air amount is determined, that is, the time from the current time until the intake valve closes.If fuel is not injected independently in each cylinder, the time from the fuel injection valve Although it is determined by taking into consideration the flight time of fuel to the combustion chamber, etc., this predicted time T is determined even if the crank angle from the current moment to the predicted light is the same. Since m5ec becomes shorter as the engine rotational speed increases, it is preferable to change it depending on the operating conditions such as the engine rotational speed (for example, it is shortened as the engine rotational speed increases). In the next step 10B, the following equation is used using the intake pipe pressure PM detected by the pressure sensor and A/D converted via the RC filter, the weight coefficient n, and the corrected intake pipe pressure PMTAI in the steady state. The initial value PMCRT is calculated according to the following.

P gate CRT = PM+ - (PMTAI-PM)
(26) In the next step 110, the initial value PMCRT calculated in step 106 is weighted by the coefficient n.
Then, the predicted value PMFWD of the intake pipe pressure is calculated by repeating the calculation of the weighted average value N-1 times according to the following 2 using the intake pipe pressure PMTAI in the steady state.

...(27) As explained above, the predicted value PMFWD of the intake pipe pressure is
It is determined by repeatedly calculating a weighted average value N times using the intake pipe pressure PM detected by the pressure sensor as an initial value.

In the next step 112, the predicted value PMFW of the intake pipe pressure is
A basic fuel injection time TP is calculated from D and the engine rotational speed NE, and in step 114, a fuel injection time TAU is calculated by correcting the basic fuel injection time TP with a correction coefficient FK determined by intake air temperature, engine cooling water temperature, etc. .

Then, in a fuel injection amount control routine (not shown), at the fuel injection timing, the fuel injection valve is opened for a time corresponding to the fuel injection time TAU, thereby controlling the fuel injection amount.

Next, correction of an internal combustion engine equipped with a supercharger will be explained. In this engine, a pressure sensor is installed upstream of the throttle to detect the pressure upstream of the throttle valve. and,
In step 100 of FIG. 1, the pressure on the upstream side of the throttle valve is taken in place of the atmospheric pressure, and in step 102, correction is performed based on the following equation, and the fuel injection time is calculated in the same manner as in the above embodiment.

PMTAI←(PMTA+K) Throttle valve upstream pressure...(28) In this case, the table in FIG. 12 is created using values measured under atmospheric pressure without operating the supercharger.

In addition, the A/D of the throttle opening is executed every predetermined time.
Although the conversion timing may coincide with the fuel injection time calculation timing executed at predetermined time intervals, there is a maximum time shift corresponding to the calculation period ΔL. Therefore, by averaging this deviation time (0+ΔL)/2, T, ±Δt/2 hours ahead, 6
The intake pipe pressure may also be predicted. In addition, in the above example, the weighting is calculated by calculating a coefficient assuming that the throttle opening and the engine rotation speed do not change. Since it may change, the intake pipe pressure is predicted by determining whether the throttle opening and engine speed are increasing or decreasing, and the weighting coefficient is corrected according to this tendency. In addition, although an example has been described above in which the fuel injection amount is corrected by correcting the intake pipe pressure etc. in a steady state, the fuel injection amount may be corrected directly. Above, an example was explained in which the amount of intake air is calculated indirectly from the intake pipe pressure and the fuel injection amount is corrected, but the amount of intake air is directly calculated from the amount of air passing upstream of the throttle valve and the amount of fuel injection is corrected. You can do it like this.

[Brief explanation of the drawing]

Fig. 1 is a flowchart showing the fuel injection amount calculation routine of the embodiment of the present invention, Fig. 2 is a diagram for explaining the principle of the first method of calculating the current intake pipe pressure, and Fig. 3 is the above-mentioned diagram. A line diagram showing changes in the actual intake pipe pressure in the intake pipe over time in the first method, FIG. 4 is a block diagram for explaining the second method of calculating the current intake pipe pressure, and FIG. Conventional intake pipe determined by throttle opening and engine speed
Figure 6 is a diagram showing the difference between the pressure and the actual intake pipe pressure. Figure 7 (1
), (2), and (3) are the throttle opening of the naturally aspirated engine,
Diagram showing changes in intake pipe pressure PMTA in steady state and current intake pipe pressure PMCRT, Fig. 8 (1), (2)
9 is a diagram showing changes in intake pipe pressure PMTA and PMCRT of a supercharged engine, FIG. 9 is a schematic diagram of an internal combustion engine equipped with a fuel injection amount control device to which the present invention can be applied, and FIG. 10 is an idle switch Fig. 11 is a block diagram showing details of the control circuit in Fig. 9, Fig. 12 is a diagram showing a map of intake pipe pressure in a steady state, Fig. 13 14 is a diagram showing a map of coefficients related to weighting of the weighted average value, FIG. 14 is a diagram showing a map of basic fuel injection time, and FIG. 15 is a flowchart showing a routine for calculating the correction value K. 8... Throttle valve, 10... Throttle opening sensor, 48... Rotation angle sensor.

Claims (1)

[Claims] (1) Calculate the current intake air amount based on the throttle opening degree and engine rotational speed, and calculate the predicted value of the intake air amount for a predetermined period of time after the calculation time based on the calculated current intake air amount, In a fuel injection amount control method for an internal combustion engine that controls the fuel injection amount based on the obtained predicted value and engine rotational speed, atmospheric pressure or pressure upstream of the throttle valve is detected, and the detected atmospheric pressure or the pressure upstream of the throttle valve is A fuel injection amount control method for an internal combustion engine, comprising correcting a predicted value of an intake air amount based on side pressure.