JPS63289237A - Fuel injection quantity controlling method for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent the turbulence of exhaust emission or the like by detecting a physical quantity other than a throttle opening corresponding to a suction air quantity and correcting a prediction value of the suction air quantity according to the detected physical quantity to reduce an error in the prediction value from a real value. CONSTITUTION:A throttle valve 8 of an internal combustion engine 20 is provided with a throttle opening sensor 10. A distributor 40 connected to an ignition plug 38 is provided with a rotational angle sensor 48. Detection signals from the sensors 10 and 48 are input to a control circuit 44. The control circuit 44 computes a present suction air quantity according to each detection signal, and also computes a prediction value of a suction air quantity at a predetermined time elapsed according to the present suction air quantity computed above. Then, a fuel injection quantity is controlled according to the prediction value and an engine speed. At this time, a physical quantity other than the throttle opening corresponding to the suction air quantity, e.g., a suction pressure is detected by a pressure sensor 6, and the prediction value is corrected according to the physical quantity.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for controlling the amount of fuel injection for an internal combustion engine, and particularly for an internal combustion engine that controls the amount of fuel injection based on the throttle opening and the engine rotation speed. The present invention relates to a fuel 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 of 3 is required to remove engine pulsation components. By processing the pressure sensor output through a filter of ~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 rises suddenly, 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 the pipe 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 increase/decrease corrections such as acceleration increase and deceleration i%&it are performed, but during transient periods there is a time delay in the detected intake pipe pressure, so the entire operation is stopped. It is impossible to completely control the air-fuel ratio to the target air-fuel ratio in this region.

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-mentioned throttle opening is the throttle opening that is output from the throttle opening sensor, which is composed of a contact fixed to the rotary wheel of the throttle valve and a variable resistor connected to a power source at one end and grounded at the other end. is detected by a voltage proportional to . 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 applicant calculates the intake pipe pressure in a steady state based on the throttle opening and engine rotation speed that have no response delay with respect to the actual intake pipe pressure, and calculates the intake pipe pressure in a steady state. The intake pipe pressure at the time when the amount of air taken into the engine is determined based on the calculated intake pipe pressure by correcting the transient response delay and calculating the intake pipe pressure without phase lead or phase lag. A method has already been proposed in which the amount of fuel injection is controlled based on this predicted value and the engine rotational speed (Japanese Patent Application No. 1982-51056).

[Problem that the invention seeks to solve]

However, in the method already proposed by the applicant,
Since the intake pipe pressure at the time when the amount of air taken into the engine is determined only by calculation without considering the actual intake pipe pressure, the predicted value is the deviation of the intake pipe pressure in the calculated steady state. There are problems in that accuracy may deteriorate due to the influence of

The present invention has been made to solve the above-mentioned problems, and is capable of controlling the fuel injection amount by determining the intake pipe pressure with high accuracy by considering the actual intake pipe pressure, etc. The purpose of the present invention is to provide an injection amount control method.

[Means for solving problems]

In order to achieve the above object, the present invention calculates the current intake air amount based on the throttle opening degree and the engine rotation speed,
An internal combustion engine that calculates a predicted value of the intake air amount for a predetermined time ahead from the calculated current intake air amount based on the calculated current intake air amount, and controls the fuel injection amount based on the calculated predicted value and the engine rotation speed. The fuel injection amount control method is characterized in that a physical quantity corresponding to the amount of intake air drawn into the engine combustion chamber and other than the throttle opening is detected, and a predicted value of the intake air amount is corrected based on the detected physical quantity. do.

[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, a physical quantity corresponding to the amount of intake air taken into the engine combustion chamber and other than the throttle opening is detected, and the predicted value of the intake air amount calculated above is corrected by the detected physical quantity, and this correction is performed. The fuel injection amount is controlled based on the predicted value and the engine rotation speed. In this way, the predicted value of the intake air amount is corrected using the detected physical quantity, so even if there is an error in the calculated predicted value, it will be corrected to the true value, and this will reduce disturbances in exhaust emissions, etc. is prevented. Note that the amount of air passing upstream of the throttle valve and the intake pipe pressure downstream of the throttle valve can be used as the above-mentioned physical quantities.

〔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 physical quantity, so the error of the predicted value with respect to the true value is reduced, and disturbances in exhaust emissions are prevented. The effect is that it can be done.

[Description of Embodiments] The present invention can take the following embodiments when calculating the current intake air amount based on the throttle opening degree and the engine rotation speed. Note that an example in which the intake air amount is indirectly detected from the intake pipe pressure downstream of the throttle valve will be described below. Therefore, hereinafter, the physical quantity corresponding to the intake air amount will be explained as intake pipe pressure.

The first Bill calculates 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 sets this intake pipe pressure as the current intake pipe pressure. It is something.

The principle of the first aspect 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 engine E, the air pressure in the intake system (intake pipe absolute pressure) is p [nun)Igabs,
], the volume of the intake system is V[j! ], the weight of the air existing in the intake system is Q [g], the absolute temperature of the air in the intake system is T ['K], the atmospheric pressure is Pc [mmHgabs,], and Let the weight of air per unit time taken into the combustion chamber be ΔQ+ [g/see], and the weight of air per unit time taken into the intake system after passing through the throttle valve Th be ΔQz [g/sec]. The weight of air in the intake system within time Δ is (ΔQ2−ΔQ,)
If the Boyle-Charles law is applied to the air in the intake system, assuming that the pressure of the air in the intake system has changed by ΔP, the following equation (1) is obtained.

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

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

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 is v8 , the engine rotation speed is NE [r pm]
, the air weight per unit time ΔQ1 taken into the combustion chamber of the engine is expressed by the following equation (4), where η is the intake efficiency.

ΔQ, = ψ・A, P]-]1 ... (3) (3) above
, by substituting equation (4) into equation (2), the following equation (5) is obtained.

Here, if we take the limit of ΔL−+O, we get becomes.

Now, considering the response near pressure P, (≠PC), the pressure is P
Assuming that o has changed to P and +P, if Po +p (however, P is a small value) is substituted for P in (6) 2 above, the following equation (7) is obtained.

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

m-・□・η (P, +P) 2■60 ...(9) here, Then, the above equation (9) becomes as follows.

t If the above equation 02) is transformed as shown in the following 02 and both sides are integrated, and the integral constant is C, the following equation 04 is obtained.

1-fog (-aP+b)=t+c・04
) Here, when 1=0, the initial value of P is Po, so from the above equation 04, the integral constant C is as follows.

■ C=-1! og(-aP+b) ・”(15) Above (
P is calculated from equations 141 and 151 as follows.

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

Therefore, by measuring the opening surface 41A of the throttle valve, that is, the throttle opening TA, the engine speed NE, and the elapsed time from the time when the throttle opening changes, and substituting it into the above (+6)2, the current intake pipe pressure P can be found. Then, based on the current intake pipe pressure P obtained in this way, a predicted value for a predetermined time ahead is calculated, and this predicted value is corrected using the detected physical quantity, and based on the corrected predicted value and the engine rotation speed NE. Then, calculate the basic fuel injection time TP, correct this basic fuel injection time TP according to the intake temperature, engine cooling water temperature, etc. to find the fuel injection time, and open the fuel injection valve for a time corresponding to this fuel injection time. By doing so, the amount of fuel required by the engine can be injected.

By the way, if the current intake pipe pressure P of the above-mentioned formula 061 is expressed in a graph as shown in Fig. 3, P=P at 1-0,
, t-+ω (steady state), this is the output of the first-order lag element such that P=b/a (intake pipe pressure PMTA in steady state). Therefore, the intake pipe pressure PMTA in the steady state is calculated based on the throttle opening TA and the engine speed NE, and the intake pipe pressure PMTA in the steady state is expressed by the transfer function G (s) of the following zero equation. The current intake pipe pressure may be calculated by processing using the first-order delay element.

G(s)=□...θTs+where, S is a Laplace transform operator and T is a time constant.

That is, in the first case B, 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.

Further, in a second aspect, the intake pipe pressure in a steady state is calculated at a predetermined period based on the throttle opening degree and the engine rotation speed, and the time constant regarding the change in the intake pipe pressure during a transient period and the predetermined period are calculated. 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 embodiment will be explained. The block diagram of the first-order lag element is shown in Figure 4, where the input is 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.

...QI Here, if t2 is the current calculation timing and tl is the past calculation timing, the following equation (21) is obtained.

-(Lz-tt) ・(x (tt) -y (
tt))+y (tt) = Y (tz)...
・(21) In the above (21), x (tg) is the intake pipe pressure P M T A , )' (tt
) is the current intake pipe pressure PMSM+, )'(tt) is the past intake pipe pressure PMSMt-+, tx tt
If (-∆) is the operation period, + P M S M
r −+ = PM S M r (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 PMS
It is shown that the current intake pipe pressure P M S Mi can be calculated by calculating the weighted average with the weight of M i -, set to n-1 and the weight of the intake pipe pressure PMTA in the steady state set to 1. There is. Also, the weight coefficient n
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 Δt based on the throttle opening degree and the engine rotational speed, and a coefficient related to the weighting is calculated using a time constant T regarding changes in intake pipe pressure during transient periods and a predetermined period Δt. The weighted average value PMSMi-+ calculated in the past by increasing the weight of the weighted average calculated in the past (i P MSMi-, According to the above formula (23), the weighted average value P M S Mi
By calculating , the current intake pipe pressure can be found.

Note that, as understood from the above equation 00.00, the time constant T = 1/a becomes smaller as the engine rotational speed NE becomes larger, and becomes smaller as the throttle opening degree TA becomes larger. In this way, the time constant is expressed by a function using the throttle opening degree TA and the engine rotational speed NE as variables. Therefore, if the calculation period Δt is constant, the weighting coefficient n can be determined by a function using the throttle opening TA and the engine rotational speed NE as variables. In addition, since the intake pipe pressure PMTA in the steady state is uniquely determined by the throttle opening TA and the engine rotation speed NE, the intake pipe pressure PMTA in the steady state can be used instead of the throttle opening TA and the engine rotation speed NE. The weighting coefficient n may be determined depending on the engine rotational 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 there is an error in the past intake pipe pressure PMSM&-t, an error will also occur in the predicted value, so in this embodiment, the air taken into the engine is Calculation cycle Δt is the time it takes to determine the amount
The number of calculations is calculated by dividing by A 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, and this predicted value is corrected with the detected physical quantity, and then the corrected predicted value. 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.

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

FIG. 7 is a schematic diagram of an 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 10 is attached to the throttle valve 8 to detect the opening of the throttle valve 8. The throttle opening sensor 10 is the eighth
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 the contact lOB 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 contactor 10B. 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 14 composed of a thermistor for detecting the temperature of intake air is attached to the wall of the intake pipe on the upstream side of the intake pipe. 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 m5e) to remove the pulsating component of the intake pipe pressure.
c) and is processed by a filter 7 (see FIG. 9) composed of a CR filter or the like with good response. 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 ISO valve 16 is attached to the bypass path 15 and is composed of a pulse motor 16A having a four-pole stator and a valve body 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 cylinder group, or to all cylinders simultaneously. .

The combustion chamber 25 communicates with a catalyst bag W (not shown) filled with a three-way catalyst via an exhaust valve 27, an exhaust port 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°C, 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. 9, a microprocessing unit (MPU) 60, a read-only memory (ROM) 6
2. Random access memory (RAM) 64, backup RAM (BU-rlAM) 66, input/output capo
Toro day, input port door 0, output port door 2.74.76
and a bus 75 such as a data bus or a control bus that connects these. An analog-to-digital (A/D) converter 78 and a multiplexer 80 are connected in sequence to the input/output capotro 8, and the intake temperature sensor 14 is connected to the multiplexer 80 via a buffer 82. Water temperature sensor 34 and throttle opening sensor 10 are connected via buffer 84 and buffer 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. The input/output capotro 8 is the A/D converter 7.
8 and multiplexer 8o, and sequentially outputs the intake temperature sensor 14 output, the pressure sensor 6 output input via the RC filter 7, the water temperature sensor 34 output, and the throttle opening sensor 10 output according to the control signal from the MPU. Control is performed to perform A/D conversion at a predetermined cycle.

The 02 sensor 3o 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 valve via a drive circuit 96. It is connected to the pulse motor 16A.

Next, a first embodiment in which the second aspect is applied to the internal combustion engine will be described. The ROM 62 contains a control routine program of the first embodiment of the present invention, which will be explained below, and the first
A map of intake pipe pressure PMTA in a steady state determined by throttle opening TA and engine rotation speed NE shown in Figure 0,
The map of the coefficient n related to the weight determined by the engine speed NE and steady state intake pipe pressure PMTA (or throttle opening TA) shown in FIG. 11, and the actual intake pipe pressure-MSM shown in FIG. A basic fuel injection time TPO map defined by the engine speed NE and the engine speed NE is stored in advance. Intake pipe pressure PM in steady state shown in Figure 10
The TA map is throttle opening TA and engine rotation speed N.
It is created by setting E, measuring the intake pipe pressure corresponding to the set throttle opening TA and engine rotational speed NE, and using the value when the intake pipe pressure is stabilized. 1st
The map of the coefficient n related to the weight shown in Figure 1 is obtained by measuring the time constant T during the intake pipe pressure response (indicial response) when the throttle valve is opened in steps, and using this measured value and the execution period Δ of the calculation routine. From Musee to T/Δt(!-
1n) is the engine rotational speed NE and the actual intake pipe pressure PMTA.
(or throttle opening TA). The basic fuel injection time TP map shown in FIG. 12 is created by setting the engine speed and intake pipe pressure and measuring the basic fuel injection time TP that provides the target air-fuel ratio (for example, the stoichiometric air-fuel ratio). .

Next, a predetermined period of time (for example, 8Ils) according to the first embodiment of the present invention.
The fuel injection time TAU calculation routine executed each time ec) will be explained based on FIG. In step 100, the engine rotation speed NE, the A/D converted throttle opening T
The A/D conversion of the throttle opening and the intake pipe pressure is carried out every predetermined time (for example, 8III seconds) (not shown). This is done by an interrupt routine that is executed. In the next step 102,
The intake pipe pressure PMTA in a steady state is calculated from the map shown in FIG. 1O from the engine rotational speed NE and the throttle opening TA. In the next step 104, the engine rotation speed NE and the intake pipe pressure P in the steady state calculated in step 102 are determined.
A coefficient n regarding weight is calculated from the map shown in FIG. 11 based on the MTA.

In the next step 106, the number of calculations from the current time to the predicted intake pipe pressure time N=To/Δt is calculated by dividing the time Tomsec from the current time to the predicted intake pipe pressure time by the calculation cycle ΔL (for example, 8 m5ec). Calculate. This predicted time T ofillec is calculated from the current time to the intake air fi 6! In other words, the time from the current time until the intake valve closes can be adopted.If fuel is not injected independently in each cylinder, the flight time of fuel from the fuel injection valve to the combustion chamber, etc. can also be taken into account. However, even if the crank angle from the current moment to the predicted light is the same, this predicted time T, m5ec becomes shorter as the engine rotation speed increases, so it is preferable to change it depending on the operating conditions such as the engine rotation speed. (For example, shorten it as the engine speed increases). In the next step 108, the intake pipe pressure PM detected by the pressure sensor and A/D converted via the RC filter, the coefficient n regarding the weight, and the intake pipe pressure PMTA in the steady state are used to obtain an initial value according to the following formula. Calculate PMCRT.

■ PMCRT = PM+ - (PMTA-PM)
...(24) In the next step l'IO, the initial value PMCRT calculated in step 106 and the weighting are
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 formula using n and the intake pipe pressure PMTA in a steady state.

PMFenD 4- PMCRT+-(PMTA
-PMCRT) N-1 times... (25) 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 TAtJ, thereby controlling the fuel injection amount.

Next, a routine of a second embodiment of the present invention will be explained. 1st
FIG. 4 shows a routine that is executed every predetermined time (for example, 8 m5ec). In step 116, the intake pipe in a steady state is determined from the engine rotational speed NE and throttle opening TA based on the map shown in FIG. 1θ. Calculate pressure PMTA. In the next step 118, the correction coefficient K calculated in step 124 and stored in the RAM, which will be explained below, is loaded, and in step 120, the intake pipe pressure in the steady state corrected by the engine rotational speed NE and the correction coefficient K is K-PMTA is used to calculate the weighting coefficient n1 from the map shown in FIG. In the next step 122, the weighted average value PMCRT
In step 124, the weighted average (lIP M) calculated in step 122 is calculated as the ratio (PM/P
MCRT) is stored in a predetermined area of the RAM as a correction coefficient.

PMCRT 4-PAA CRT + -(K -PMTA
-P A CRT) ... (26) Here, the weighted average (a P M CRT and intake pipe pressure PM ratio, that is, the correction coefficient, has the following effects in the steady state due to the map deviation in Fig. 10). It is considered to be an error of the intake pipe pressure with respect to the actual intake pipe pressure PM, and if there is no error, = 1, and if the calculated intake pipe pressure, that is, the weighted average value PMCRT is greater than the detected intake pipe pressure PM. is K<1, and when the calculated intake pipe pressure is smaller than the detected intake pipe pressure, K>1. Therefore, when the calculated intake pipe pressure is smaller than the detected intake pipe pressure, When the correction coefficient K becomes larger than 1, the intake pipe pressure PM in the steady state
TA is corrected to become larger, and when the calculated intake pipe pressure is greater than the detected intake pipe pressure, the correction coefficient K becomes smaller than 1, and the intake pipe pressure PMTA in the steady state
is corrected so that it becomes smaller.

FIG. 13 shows a fuel injection time TAU calculation routine executed every predetermined time (for example, 3m5ec).
In step 126, the engine rotation speed NE, throttle opening TA, intake pipe pressure PM, and correction coefficient K are taken in, and in step 128, the engine rotation speed NE and throttle opening TA are used to determine the steady state from the map shown in FIG. 0th order step 1 to calculate the intake pipe pressure PMTA of
30, the engine rotational speed NE and the steady state intake pipe pressure K - PMTA corrected by the correction coefficient K are calculated as follows:
In the zero-order step 132 of calculating the coefficient n2 regarding the weight based on the map of FIG. 1, step 106 of FIG.
The number of calculations N is calculated in the same manner. Next step 13
In step 4, an initial value PMCRT is calculated according to the following equation using the intake pipe pressure PM, the weighting coefficient n', the correction coefficient, and the steady state intake pipe pressure PMTA.

PMCII74-PM + -(K-P phylum TA-P
(27) Then, in step 136, the calculation of the weighted average value is repeated N-1 times as shown in the following formula, and the calculated value is used as the predicted value PMFWD of the intake pipe pressure.
shall be.

PMFWD -PMCRT+ -(K ・PMTA-P
? 1CRT) N-1 times... (28) As a result of the above, the intake pipe pressure in the steady state is corrected according to the error between the detected intake pipe pressure and the calculated intake pipe pressure, and is also detected. A weighted average value is repeatedly calculated N times using the calculated intake pipe pressure as an initial value, and the value of this calculation result is set as the predicted value PMFWD of the intake pipe pressure.

In the next step 138 and step 140, the fuel injection time TAU is calculated in the same manner as steps 112 and 114 in FIG.

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, it is shifted by a time corresponding to the maximum calculation cycle ΔL.

Therefore, by averaging this deviation time (0+Δt)/2, T
The intake pipe pressure may be predicted for 0±Δt/2 hours ahead.Also, in the above example, a weighting coefficient is calculated assuming that the throttle opening and engine speed do not change. Since the throttle opening and engine rotational speed may change during the elapse of T, m5ec from the current time, it is necessary to determine whether the throttle opening and engine rotational speed are increasing or decreasing, and check the The weighting may be done by correcting the coefficient to predict the intake pipe pressure.In addition, the above example describes an internal combustion engine in which the intake air amount is indirectly determined from the intake pipe pressure and the fuel injection amount is controlled. Although described above, the present invention can also be applied to an internal combustion engine in which the amount of intake air is directly determined from the amount of air passing upstream of the throttle valve to control the amount of fuel injection. Furthermore, the ignition timing may be controlled using a method similar to the above control.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing the fuel injection amount calculation routine of the first embodiment of the present invention, FIG. 2 is a diagram for explaining the principle of the first embodiment, and FIG. 3 is a diagram showing the inside of the intake pipe in the first embodiment. Fig. 4 is a block diagram for explaining the second aspect, and Fig. 5 shows the intake pipe pressure determined by the conventional throttle opening and engine speed. Fig. 6 is a diagram showing the difference between the conventional intake pipe pressure and the actual intake pipe pressure; The figure 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, Figure 8 is an equivalent circuit diagram of a throttle opening sensor equipped with an idle switch, and Figure 9 is the control circuit of Figure 7. Fig. 10 is a diagram showing a map of intake pipe pressure in a steady state, Fig. 11 is a diagram showing a map of coefficients related to weighting of weighted average values, and Fig. 12 is a diagram showing basic fuel injection. A diagram showing a time map, FIG. 13 is a flowchart showing a fuel injection time calculation routine in the second embodiment of the present invention, and FIG. 14 is a flowchart showing a routine for calculating a correction coefficient in the second embodiment. 8... Throttle valve, 10... Throttle opening sensor, 4th... Rotation angle sensor.

Claims (1)

[Claims] (1) Calculate the current intake air amount based on the throttle opening 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 a calculated predicted value and engine rotational speed, a physical quantity corresponding to the amount of intake air taken into the engine combustion chamber and other than the throttle opening Detects the physical quantity of
A fuel injection amount control method for an internal combustion engine, characterized in that a predicted value of an intake air amount is corrected based on a detected physical quantity.