JPS63280839A - Fuel injection quantity controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To permit the always correct fuel feed by calculating the fuel feed quantity on the basis of the throttle valve opening degree and the engine revolution speed in ordinary case and obtaining the fuel feed quantity on the basis of the physical quantity corresponding to the intake air quantity other than the throttle valve opening degree, and the engine revolution speed, when a throttle valve opening degree sensor is in trouble. CONSTITUTION:A bypass passage 15 as subintake passage is connected with a main intake passage having a throttle valve 8 installed, making a detour around the throttle valve 8, and an ISC valve 16 having a pulse motor as driving source is installed midway in the bypass passage 15. During the engine operation, it is judged in a control circuit 14 if a throttle opening degree sensor 10 operates normally, and when the normal operation is judged, the fundamental fuel injection time is calculated on the basis of the output of the throttle valve opening degree sensor 10 and the engine revolution speed obtained in a revolution angle sensor 48. When it is judged that the throttle opening degree sensor 10 is in trouble, the fundamental fuel injection time is calculated on the basis of the output of an intake pipe pressure sensor 6 and the engine revolution speed, and a fuel injection valve 24 is controlled by properly correcting the fundamental fuel injection time.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a fuel injection amount control device for an internal combustion engine, and in particular to a fuel injection amount control device for an internal combustion engine that controls the fuel injection amount based on a throttle opening and an engine rotation speed. This invention relates to an injection amount control device.

[Prior art] Conventionally, the amount of air passing upstream of the throttle valve and the engine rotational 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 amount of air, the basic fuel injection time is calculated by considering the air-fuel ratio based on the intake air amount per engine revolution, and this basic fuel injection time is corrected based on intake air temperature, engine cooling water temperature, etc., and then fuel injection is performed. The amount of fuel injection is controlled by determining the time and 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. The intake pipe pressure is detected by processing the pressure sensor output through a 3 to 5 m5ec filter. 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 closes suddenly and the actual intake pipe pressure rises rapidly, but there is a time delay in the detected intake pipe pressure, resulting in a value that is smaller than the actual intake pipe pressure. Since the basic fuel injection time is calculated based on the intake pipe pressure, the air-fuel ratio becomes over-lean, deteriorating acceleration response and 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 to increase/decrease acceleration, deceleration range, etc. However, during transient periods, 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 speed, an mff1 sensor such as an air flow meter or Karman vortex flow meter is installed upstream of the throttle valve to detect the air amount. Since the flow rate sensor is installed upstream of the throttle valve, a change in the output of the flow rate sensor causes a response delay with respect to a change in the actual amount of intake air, resulting in the same problem as described above.

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 Publication No. 122237 discloses that the basic fuel injection time is calculated based on the throttle opening and the engine speed to control the fuel injection amount. 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, if a failure occurs such as a disconnection of the power supply connected to the throttle opening sensor or a short circuit in the throttle opening sensor, the throttle opening sensor output will not correspond to the throttle opening, and the amount of fuel injected will be excessive or insufficient. For this reason, conventionally, as shown in Japanese Patent Laid-Open No. 60-224951, an air flow sensor for detecting the amount of intake air is provided in addition to the throttle opening sensor, and when the throttle opening sensor is normal, the throttle opening sensor The fuel injection amount is controlled based on the output, and when the throttle opening sensor fails, the fuel injection amount is controlled based on the airflow sensor output.

[Problem that the invention seeks to solve]

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. Therefore, the intake pipe pressure P (TA, NE) determined by the throttle opening degree and the engine rotational speed becomes a value whose phase is advanced from the actual intake pipe pressure P, as shown in FIG. Note that PM is the intake pipe pressure obtained from the pressure sensor. Furthermore, as shown in Fig. 6, the basic fuel injection time TP (T
A, 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.

The present invention has been made to solve the above problems, and uses the throttle opening without delay in response to changes in the actual intake air amount to obtain the intake air amount without phase advance or phase lag, that is, the actual intake air amount. By predicting the amount of air,
To provide a fuel injection amount control device for an internal combustion engine that is capable of injecting the amount of fuel required by the engine and also capable of injecting just the right amount of fuel when a throttle opening sensor fails. With the goal.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a throttle opening detection means for detecting a throttle opening, a rotation speed detection means for detecting an engine rotation speed, and a throttle opening detection means for detecting an engine rotation speed. an intake air amount calculating means for calculating an intake air amount in a steady state based on the opening degree and the detected engine rotational speed; A failure occurs in the correction means for correcting the response delay, the physical quantity detection means for detecting a physical quantity corresponding to the amount of intake air taken into the engine combustion chamber and other than the throttle opening, and the throttle opening detection means. failure detection means for detecting whether or not the failure has occurred; and when the occurrence of the failure is not detected, the fuel injection amount is controlled based on the intake air amount corrected by the correction means and the detected engine rotation speed; The fuel injection amount control means controls the fuel injection amount based on the physical quantity detected when the occurrence of the failure is detected and the engine rotational speed detected.

[Operation] According to the present invention, when the occurrence of a failure in the throttle opening detection means is not detected by the failure detection means as shown in the block diagram shown in FIG. 1, the throttle opening detected by the throttle opening detection means The intake air amount in a steady state is calculated by the intake air amount calculation means A based on TA and the engine rotation speed NE detected by the rotation speed detection means.

The intake air amount in a steady state calculated by the intake air amount calculation means A is corrected by the correction means B by the amount of response delay of the intake air amount during transient times. As this correction means B, a first-order lag element can be used. The intake air amount corrected by the correction means B is input to the fuel injection amount control means C, and the fuel injection time is calculated based on the engine rotational speed NE input to the fuel injection amount control means to determine the fuel injection amount. controlled. On the other hand, when the failure detection means detects the occurrence of a failure in the throttle opening detection means, the fuel injection amount control means sets a physical quantity corresponding to the intake air amount other than the throttle opening detected by the physical quantity detection means E to the engine. The fuel injection time is calculated based on the rotational speed NE, and the fuel injection amount is controlled. As the physics corresponding to the amount of intake air other than the throttle opening degree, the intake pipe pressure on the downstream side of the throttle valve or the amount of air passing through the upstream side of the throttle valve can be adopted.

〔Effect of the invention〕

As explained above, according to the present invention, the actual intake air amount is predicted and the fuel injection amount is controlled based on this intake air amount and the engine rotational speed. This allows the air-fuel ratio to be controlled to the target air-fuel ratio to prevent over-rich or over-lean air-fuel ratios during transient periods, and also to prevent other detection when the throttle opening detection means fails. Since the amount of fuel injection can be controlled by the output of the means, it is possible to prevent excess or deficiency of the amount of fuel injection when the throttle opening detecting means fails, thereby achieving the effect of ensuring good operation.

[Explanation of aspects]

In implementing the present invention, the following embodiments may be adopted.

The first aspect is that when the fuel injection amount control means controls the fuel injection amount when the throttle opening detection means is not malfunctioning (normal state), the throttle opening is controlled based on the throttle opening and the engine rotational speed. Calculate the intake pipe pressure using the time elapsed since the temperature change as a variable, calculate the basic fuel injection time based on the calculated intake pipe pressure and engine rotation speed, and calculate the basic fuel injection time based on the calculated basic fuel injection time. It controls the amount of fuel injection.

The principle of the aspect of Box 1 will be explained below. As shown in Fig. 2, considering the intake system from the throttle valve Th to the intake valve of engine E via the surge tank S, the air pressure in the intake system (intake pipe absolute pressure) is p [mmHgabs, ]
, the volume of the intake system is V[f], 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 weight of air per unit time taken into the combustion chamber of engine E from the intake system is ΔQ+ [g/5ecl, the air that passes through the throttle valve Th and enters the intake system. Let the air weight per unit time inhaled by ΔQt [g/see] be expressed as
Assuming that the weight of the air in the intake system changes by (ΔQ2-ΔQ+)・Δ within , and the pressure of the air in the intake system changes by ΔP, apply the Boyle-Charles law to the air in the intake system. Then, it becomes as shown in the following equation (1).

(P+Δp)v= (Q+(ΔQ knee ΔQ,)Δt l 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.

Here, when 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 8. Engine rotation speed NE [r pml
, the air weight ΔQ per unit time taken into the combustion chamber of the engine is expressed by the following equation (4), where η is the intake efficiency.

A Q z = ψ・A Dr[:T-(3) Above (3
), and by substituting equation (4) into equation (2), the following equation (5) is obtained.

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

Now, considering the response near the pressure PO (≠Pc), the pressure is P
If Pa +P (however, P is a small value) is substituted for P in the above equation (6) as a change from o to P and +P, the following equation (7) is obtained.

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

...(9) here, b=yaψAPc−P.

Then, the above equation (9) becomes as follows.

Transform the above equation as shown below and integrate both sides,
Letting the integral constant be C, the following 04) 2 is obtained.

-1og (-aP+b)=t+C-(mwhere 1=
When P is 0, the initial value of P is Po, so from the above equation 041, the integral constant C is as follows.

C=-p, og(-aP+b) -(15) 04 above
P is calculated from the formula and formula 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 from the time when the throttle opening changes, and substituting them into the above 002, the actual intake pipe pressure P can be found. Can be done. Then, based on the actual intake pipe pressure P and engine rotational speed NE obtained in this way, the basic fuel injection time TP is obtained by, for example, the calculation shown in 2 below. The fuel injection time is calculated by correcting it according to the air temperature, engine cooling water temperature, etc., and by opening the fuel injection valve for a time corresponding to this fuel injection time, the throttle opening detection means detects the amount of fuel required by the engine when it is normal. Can be injected.

TP=ni-, IT/NE However, K is a constant.

By the way, when the intake pipe pressure P of the above equation 06) is expressed in a graph as shown in Fig. 3, when 1=0, P-p, t→
At the limit of ω (steady state), it is the output of the first-order lag element such that P = b / a (intake pipe pressure PMTA in steady state). Therefore, throttle opening TA and engine rotation speed N
Calculate the intake pipe pressure PMTA in the steady state based on E and calculate the intake pipe pressure PMTA in the steady state as follows θ'7)
The actual intake pipe pressure may be calculated by processing using a first-order lag element expressed by the transfer function G (s) of the equation.

Also, S is a Laplace transform operator, and T is a specific number.

That is, in the first aspect, 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 may be calculated using the elapsed time as a variable by processing the calculated intake pipe pressure in a steady state using a first-order lag element.

As explained above, according to this aspect, the actual intake pipe pressure is predicted when the throttle opening detection means is normal and the fuel injection amount is controlled based on this intake pipe pressure and the engine rotational speed. When the opening detection means is normal, the amount of fuel corresponding to the actual amount of intake air can be injected, thereby controlling the air-fuel ratio to the target air-fuel ratio and preventing over-rich and over-lean air-fuel ratios during transient times. The effect is that you can.

The second aspect is that when the fuel injection time calculation means calculates the basic fuel injection time when the throttle opening detection means is normal, the fuel injection time calculation means calculates the basic fuel injection time in a steady state at a predetermined period based on the throttle opening and the engine rotational speed. Calculates the intake pipe pressure, calculates a weighting coefficient using a time constant regarding changes in the intake pipe pressure during transition and the predetermined period, and increases the weight of the weighted average value calculated in the past. A current weighted average value is calculated using the weighted average value, the intake pipe pressure in the steady state, and the coefficient related to the weight, and a basic fuel injection time is calculated based on the calculated current weighted average value and the engine rotation speed. However, the fuel injection amount is controlled TJ based on the calculated basic fuel injection time.

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 tl is the current calculation timing and 1+ is the past calculation timing, the following equation (21) is obtained.

12-(tg-t, ) ・(x(tz)-y(t
+))+ y (t+) = y (tt) ・・
・(21) In the above (21), x (tz) is the intake pipe pressure P M T A , )' (Lx
) as the current actual intake pipe pressure P M S M = , y
(t+) is past actual intake pipe pressure PMSM+-+
, tz t+ (=Δt) is the operation period, then I゛+ P M S Mr-+ = P M S Mt
...(22), and if T/Δt=n, the following equation (23) is obtained.

...(23) In other words, the above equation (23) calculates a weighted average with the weight of the past actual intake pipe pressure PMSM+- set as n-1 and the weight of the steady state intake pipe pressure PMTA set as 1. This shows that the current actual intake pipe pressure P M S M r can be calculated. Further, the weighting coefficient n is determined by the ratio of the time constant d and the calculation period Δt.

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 the weighting coefficient is calculated using a time constant T regarding changes in intake pipe pressure during transient periods and a predetermined period ΔL. n and calculates the previously calculated weighted average value PMS11. If the weighted average value PMSMi is calculated in accordance with the above equation (23) using the weighted average value PMSMi−+ calculated in the past by increasing the weight of The actual intake pipe pressure will be determined. Therefore, in this aspect, the basic fuel injection time when the throttle opening detection means is normal is calculated based on the weighted average value (current actual intake pipe pressure) calculated as described above and the engine rotation speed, The fuel injection amount is controlled based on the calculated basic fuel injection time.

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.

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.

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.

For this reason, Mr. B calculates the number of calculations by dividing the time from the time when the intake pipe pressure in a steady state is calculated until the amount of air taken into the engine is determined by the calculation period Δ, and calculates the number of calculations. By repeating the calculation of the weighted average of equation (23) above, the weighted average value at the time when the amount of air taken into the engine is determined, that is, the actual intake pipe at the time when the amount of air taken into the engine is determined. It is preferable to predict the pressure and 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 then repeat the calculation of 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 fluctuates. The accuracy of the predicted value of the actual intake pipe pressure is further improved.

In addition, the fuel injected from the fuel injection valve adheres to the engine wall surface such as the inner wall surface of the intake manifold, and not all of the injected fuel is supplied to the combustion chamber, so this amount of fuel adhesion is corrected to adjust the fuel injection amount. Preferably controlled. This amount of fuel adhesion depends on the magnitude of the intake pipe pressure; when the intake pipe pressure is low, the amount of fuel evaporation is large (therefore, the amount of fuel adhesion is small), and when the intake pipe pressure is high, the amount of fuel evaporation is small. Therefore, the amount of fuel deposited increases.For this reason, in this embodiment,
Throttle opening detection means predicts the amount of change in the amount of fuel adhering to the engine wall from the actual intake pipe pressure calculated by weighted average when normal, and corrects the amount of fuel injection corresponding to this amount of change to the engine. It is preferable to supply the engine with an amount of fuel that corresponds to the actual amount of intake air taken in. The amount of fuel that adheres to the wall surface also changes depending on the engine temperature and engine rotation speed (the higher the engine temperature, the more fuel As the amount of evaporation increases, the amount of fuel adhesion decreases, and as the engine rotation speed increases, the air flow speed increases (and the amount of evaporation increases, so the amount of fuel adhesion decreases), which is a function of engine temperature and engine rotation speed. The amount of change in the amount of fuel adhesion may be determined as
Furthermore, since the amount of fuel adhering to the wall surface is not stabilized instantaneously, the correction amount of the fuel injection amount may be attenuated over time so that the amount of fuel adhering to the current injection is reflected in subsequent injections.

As explained above, in this aspect, the actual intake pipe pressure is predicted by calculating the weighted average value at a predetermined period when the throttle opening detection means is normal, so the elapsed time from the time when the throttle opening changes It is possible to predict the actual intake pipe pressure without measuring it, and as a result, the air-fuel ratio is controlled to the target air-fuel ratio even during transient periods, and the W
This has the effect that it is possible to prevent this from occurring.

In the above embodiment, an example was explained in which the basic fuel injection time is calculated based on the amount corresponding to the intake pipe pressure and the engine speed when the throttle opening detection means is normal. The basic fuel injection time may be calculated based on the amount corresponding to the amount and the engine rotation speed.

〔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 the fuel injection amount control device of this embodiment.

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. As shown in the equivalent circuit of FIG. 8, the throttle opening sensor 10 includes a contactor 10B fixed to the rotary wheel 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 throttle valve 8 changes, the contact state between the contact lOB and the variable resistor 10A changes, and the throttle valve 8 changes.
The contactor 10B is configured to obtain a voltage corresponding to the opening degree of 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). A temperature sensor 14 comprised of a thermistor is attached to the intake pipe wall upstream of the throttle valve 8 to detect the temperature of intake air. 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.
) 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 port 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 device (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 configured with a thermistor or the like is attached to the cylinder block 32 so as to protrude into the walk 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. A cylinder discrimination sensor 46 and a rotation angle sensor 48 are attached to the distributor 40, 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 every 720 degrees CA, for example, and the rotation angle sensor 48 outputs a cylinder discrimination signal every 720 degrees CA, for example.
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-RAM) 66, input/output capotro 8, input port door 0, output port door 2.74.76, and the data bus, control bus, etc. that connect these. It is equipped with bus 75. An analog-to-digital (A/D) converter H78 and a multiplexer 80 are connected in sequence to the input/output capotro 8.
0 is connected to an intake temperature sensor I4 via a buffer 82, and is also connected to a water temperature sensor 34 and a throttle opening sensor 1o via a buffer 84 and a buffer 85, respectively. Further, the pressure sensor 6 is connected to the multiplexer 80 via a buffer 83 and a CR filter 7 composed of a resistor R and a capacitor C. The input/output capotro 8 is connected to an A/D converter 78 and a multiplexer 8o, and outputs an intake air temperature sensor I4 and a pressure sensor 6 which is input via the CR filter 7 according to a control signal from the MPU. , the output of the water temperature sensor 34 and the output of the throttle opening sensor 10 are controlled to be A/D converted in sequence 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 via a drive amount path 96. It is connected to the pulp 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 PMSM shown in FIG. A map of basic fuel injection time TP determined by engine rotational 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 weight coefficient n shown in Fig. 1 is obtained by measuring the time constant T during the intake pipe pressure response (indicinal response) when the throttle valve is opened in steps, and using this measured value and the calculation shown in Fig. 15. It is created by determining T/Δt(#n) from the routine execution cycle Δt sec in correspondence with the engine rotational speed NE and the actual intake pipe pressure PMTA (or throttle opening TA). The basic fuel injection time TPO map shown in FIG. 12 is created by setting the engine speed and intake pipe pressure and measuring the basic fuel injection time TP at which the target air-fuel ratio (for example, stoichiometric air-fuel ratio) is achieved.

First, the main routine of this embodiment will be explained with reference to FIG. First, in step 120, it is determined whether the throttle opening sensor lO is normal. The idle switch 11 determines whether the throttle opening sensor 10 is normal or not.
It can be determined from the output and the throttle opening sensor output, and when the idle switch is off and the amount of change in the throttle opening sensor output within a predetermined time is less than a predetermined value, or when the idle switch is on and the throttle opening sensor output is greater than or equal to the predetermined value. When this happens, it is determined that a failure has occurred in the throttle opening sensor. Also, when the idle switch is off and the throttle opening sensor output is 0, or when the calculated intake pipe pressure P
A failure may be determined when the difference between the MTA and the pressure sensor output is greater than or equal to a predetermined value. When it is determined in step 120 that the throttle opening sensor is normal, a basic fuel injection time TP is calculated in step 128 based on the throttle opening TA and the engine rotational speed NE.

The calculation of this basic fuel injection time TP is explained in the 15th section.
The explanation will be based on the subroutine shown in the figure. On the other hand, when it is determined in step 120 that the throttle opening sensor has failed, in step 122 the intake pipe pressure P detected by the pressure sensor 6 and processed by the filter is
In step 124, the basic fuel injection time TP is calculated by taking in the basic fuel injection time TP, the air-fuel ratio feedback correction coefficient FAF calculated in the routine of FIG. 14, and the engine rotational speed NE. The fuel injection time TAtJ is calculated according to the following formula using a correction coefficient F determined by intake air temperature, engine cooling water temperature, etc.

TAU=TP -FAF -F Next, a routine for calculating the air-fuel ratio feedback correction coefficient FAF for feedback-controlling the air-fuel ratio will be described with reference to FIG.

First, in step 180, it is determined whether the air-fuel ratio feedback condition is satisfied. Whether or not the air-fuel ratio feedback condition is satisfied is determined according to the operating state. For example, the engine is not starting, the engine cooling water temperature is above a predetermined value (a (for example, 40'C), and the fuel is being cut. Instead, it is determined that the air-fuel ratio feedback condition is satisfied when the fuel is not being increased and the air-fuel ratio lean control is not being performed.

When it is determined in step 180 that the air-fuel ratio feedback condition is not satisfied, the air-fuel ratio feedback correction coefficient FAF is set to 1.0 in step 182, and then in step 198, the air-fuel ratio feedback correction coefficient FAF is stored in a predetermined area of the RAM. Remember.

On the other hand, if it is determined in step 180 that the air-fuel ratio feed rate condition is satisfied, step 184
It is determined whether or not the Ox sensor output indicates a rich air-fuel ratio. When it is determined that the 02 sensor output indicates a rich air-fuel ratio, the integral constant KL is calculated from the air-fuel ratio feedback correction coefficient FAF in step 186.
is subtracted, and in step 188 it is determined whether the 0□ sensor output has reversed from lean air-fuel ratio to rich.

If the determination in step 188 is affirmative, the proportionality constant SL is subtracted from the air-fuel ratio feedback correction coefficient FAF in step 190.

On the other hand, if it is determined in step 184 that the 0□ sensor output indicates a lean air-fuel ratio, then in step 192 the air-fuel ratio feedback correction coefficient FAF is set to the integral constant K.
After adding R, it is determined in step 194 whether the 0□ sensor output has reversed from rich air-fuel ratio to lean. When it is determined in step 194 that the air-fuel ratio sensor output has reversed from rich to lean, in step 196 the proportional constant SR is added to the air-fuel ratio feedback correction coefficient FAF, and then in step 198
RAM the air-fuel ratio feedback correction coefficient FAF in
is stored in a predetermined area.

Next, details of step 128 in FIG. 13 will be explained with reference to the fuel injection time calculation routine shown in FIG. 15. This routine is executed every predetermined time (for example, 8 m5ec). Throttle opening degree TA converted from A/D in step 100 (for example, A/D converted every 8 wrsec)
In the zero-order step 104, the intake pipe pressure PMTA in the steady state corresponding to the throttle opening TA and the engine rotation speed NE is calculated from the map shown in FIG. 10 in step 102. , based on the intake pipe pressure PMTA calculated in step 102 and the engine rotational speed NE taken in step 100.
A coefficient n related to weighting is calculated from the map shown in FIG.

In addition, when the map of the coefficient n regarding the weight is determined by the throttle opening degree and the engine rotational speed, the coefficient n regarding the weighting is calculated in step 104 using the throttle opening degree TA and the engine rotational speed NE taken in at step 100. You can do it like this. In the next step 106, the intake pipe pressure PMTA calculated in step 102, the coefficient n regarding the weight calculated in step 104, and the previous weighted average value PMSM calculated in step 106 during the previous execution of this routine.
The current weighted average value P M S Mi is calculated according to equation (23) described above using i-, and. In the next step 108, the basic fuel injection time TP is calculated from the map shown in FIG. 12 based on the current weighted average value PMSM and the engine rotational speed NE.

Then, in the control tl routine (not shown), the fuel injection time TAI calculated above is calculated when a predetermined crank angle is reached.
The fuel injection valve is opened for a time corresponding to J to perform fuel injection. As a result of the control as described above, when the throttle opening sensor is normal, the basic P! calculated from the throttle opening TA and the engine rotational speed NE by the routine shown in FIG. 15! The fuel injection amount is controlled based on the paddy injection time TP, and when the throttle opening sensor fails, the basic fuel injection is determined by the physical quantity corresponding to the intake pipe pressure detected by the pressure sensor, that is, the actual intake air amount, and the engine rotation speed. The fuel injection amount is controlled based on time. Therefore, even when the throttle opening sensor fails, the fuel injection amount is controlled based on the pressure sensor output, so that fuel injection without excess or deficiency can be carried out.

Next, a routine for calculating the ignition advance angle θ of the above embodiment will be explained with reference to FIG. 16. This routine is executed at every predetermined crank angle.

Note that in FIG. 16, the same parts as in FIG. 15 are designated by the same reference numerals, and the description thereof will be omitted. In step 112, a basic ignition advance angle θ□I is calculated based on the weighted average value PMSM+ calculated this time and the engine rotational speed NE. The basic ignition advance angle θ, A51, may be calculated using an arithmetic expression, or a map may be created and calculated from this map in the same manner as the basic fuel injection time. Then, in the next step 114, the basic ignition advance angle θ8^S is multiplied by a correction coefficient IK determined by the intake air temperature, engine cooling water temperature, etc. to obtain the ignition advance angle θ. Then, in an ignition timing control routine (not shown), ignition is executed by turning off the Eve knife at the basic ignition advance angle θ.

Figures 17 (1) and (2) show a comparison of the change in the air-fuel ratio during acceleration when no acceleration increase is performed in the conventional case and the change in the air-fuel ratio in this embodiment, and also show the fuel injection amount. The difference between the weighted average value PMSM in this embodiment and the conventionally detected intake pipe pressure PM is shown. As can be understood from FIG. 17, the air-fuel ratio of the conventional example has a lean spike during acceleration, but the air-fuel ratio of this embodiment is approximately flat.

As explained above, in this embodiment, when the throttle opening sensor is normal, the actual intake pipe pressure is predicted and the fuel injection amount and ignition timing are controlled to perform accurate fuel injection amount control and ignition timing control. Can be done.

Next, a second embodiment in which the present invention is applied to the above-mentioned internal combustion engine will be described. This embodiment predicts the actual intake pipe pressure when the intake air m is determined (when the intake valve is fully closed) by repeating the calculation of the weighted average value a predetermined number of times when the throttle opening sensor is normal. The fuel injection amount is controlled. Note that the fuel injection control when the throttle opening sensor fails is the same as that in the first embodiment, so a description thereof will be omitted. FIG. 18 shows the predetermined time (in this example, 3
This routine is executed every m5ec) to calculate the predicted value PMSM2 of the intake pipe pressure when the intake air amount is determined. At step 200, the engine rotational speed NE is obtained, and the throttle opening degree TA is A/D converted to obtain the throttle opening degree TA. In step 202, the intake pipe pressure PMT in the steady state corresponding to the engine rotational speed NE and the throttle opening TA is calculated from the map shown in FIG. 1O.
In the zero-order step 204 of calculating A, a coefficient n relating to weighting is calculated from the map shown in FIG. In the next steps 206 and 208, the register PMSM
Previously calculated weighted average value PMSM stored in 1
+−+ is read from the RAM and the current weighted average value PMSM is calculated based on the above equation (23), and step 2
In step 10, this weighted average value P M S ML is recorded in the register PMSMI as f and α. Next step 21
2, the time T from the current time to the predicted intake pipe pressure time
lm5ec is the calculation period Δt (=8
msec) to calculate the number of operations T, /Δt.

This predicted time Tl m5ec can be the time from the current time until the intake air ffi 1.1 constant, that is, the time from the current time until the intake valve closes.If fuel is not injected independently in each cylinder, the It is determined by taking into account the flight time of the fuel from the injection valve to the combustion chamber, etc., but even if the crank angle from the current moment to the predicted light is the same, this predicted time T, m5ec will become shorter as the engine rotation speed increases. Therefore, it is preferable to vary it depending on operating conditions such as engine rotation speed (for example, to shorten it as the engine rotation speed increases). In the next step 214, the number of operations TI/Δ
The calculation of equation (23) above is repeated several times, and in step 216, the calculated value is set as the predicted value PMSM2 of the intake pipe pressure. By repeatedly executing the weighted average value in this way, the latest weighted average value approaches the intake pipe pressure value in the steady operating state. Therefore, by determining the number of times the weighted average value is calculated as described above, T1m5e is calculated from the current time.
It is possible to predict the intake pipe pressure c ahead (the intake pipe pressure in a state closer to a steady state than at the present time).

FIG. 19 shows a routine for calculating the fuel injection time TAU at every predetermined crank angle (for example, 120° CA). 2, the basic fuel injection time TP is calculated from the map shown in FIG.

Please note that the throttle opening and engine speed may change after T1m5ec has passed from the current time.
Use the differential value of the throttle opening degree and the differential value of the engine rotational speed to predict the throttle opening degree and engine rotational speed T1m5ec ahead and get T+! The accuracy can be further improved by predicting the intake pipe pressure in the steady state ahead of asec and repeating the calculation of the weighted average value.

Weighted average value and Tl1I when calculated as above
The predicted value PMSM2 after SeC has passed is shown in Figures 20 and 2.
Shown in Figure 1. In FIG. 20, the predicted value and the theoretical value for 16 m5 ec ahead are shown, and the predicted value is approximately equal to the theoretical value. Note that the A/D conversion timing of the throttle opening may be different from the fuel injection time calculation timing.
There is a time lag corresponding to the maximum calculation cycle Δt. Therefore, by averaging this deviation time (0+Δt)/2, we get T1 ± Δt
The intake pipe pressure may be predicted for /2 hours ahead.

Next, a third embodiment of the present invention will be described. In this embodiment, when the throttle opening sensor is normal, the amount of fuel adhering to the engine wall is predicted and the fuel injection amount is corrected. In addition,
The control of the fuel injection amount when the throttle opening sensor fails is the same as described above, so the explanation will be omitted. Further, in this embodiment, the calculation of the fuel injection time TAU has been explained.

The amount of fuel adhering to the engine wall without being sucked into the engine combustion chamber is determined by the intake pipe pressure when the intake valve is closed. For example, when the intake pipe pressure accelerates from PMI to PM2, Let T1 and T2 be the fuel adhesion thickness at the intake pipe pressure of related to (determined)

Therefore, in this embodiment, a certain reference intake pipe pressure (for example,
The total adhesion amount of the injection amount to be supplied to the wall when changing the intake pipe pressure from OmmHgabs) to an arbitrary intake pipe pressure is
As shown in the figure, the intake pipe pressure when the intake valve is fully closed is stored in the ROM in advance in the form of a map.

FIG. 22 shows the predetermined crank angle (360° CA) of this embodiment.
), and in step 230, the basic fuel injection time TP is calculated from the predicted value PMSM2 of the intake pipe pressure calculated in FIG. 21 above and the engine rotational speed NE. Calculate in the same way. In the next step 232, a fuel injection amount correction coefficient FK determined by intake air temperature, engine cooling water temperature, etc. is calculated. In the next step 234, the fuel adhesion amount FM on the engine wall surface corresponding to the predicted value PMSM2 of the intake pipe pressure is determined from the map in FIG.
Calculate WET. Then, in the next step 236, the basic fuel injection time is multiplied by the correction coefficient FK, and
The fuel injection time TAU is determined by subtracting the previous fuel deposition amount FMWET OLD from the currently determined fuel deposition amount FMWET and adding it as a correction addition value. This correction addition amount represents the amount of change in fuel adhesion amount caused by a change in intake pipe pressure. Then, in step 238, the currently determined fuel adhesion amount FMWET is stored in the RAM as the previous adhesion amount FMWET OLD.

By controlling the fuel injection amount as described above, the second
As shown in Figure 3, the amount of fuel shown in the shaded area is increased, and even if the fuel adheres to the inner wall of the engine by the thickness of the fuel, the amount of fuel supplied to the engine will still reach the required value due to the additional amount of correction. Become. Note that FIG. 26 shows the throttle opening, predicted values of intake pipe pressure, and changes in air-fuel ratio.
In this example, unlike the conventional example shown by the broken line, lean spikes do not occur and the fluctuations in the air-fuel ratio are reduced.

Next, a fourth embodiment of the present invention will be described. In the third embodiment described above, the fuel injection amount was controlled by the amount of fuel adhering to each injection, but considering that the adhesion of fuel to the engine wall is not instantaneously stable, this embodiment By attenuating the correction addition amount for each injection when the fuel temperature sensor is normal and reflecting it in subsequent injections, the amount of fuel supplied to the combustion chamber is made equal to the required value. FIG. 27 shows the fuel injection calculation routine of this embodiment, for example, at a predetermined crank angle (360@CA
) is executed every time. Note that in FIG. 27, the same parts as in FIG. 22 are designated by the same reference numerals, and explanations thereof will be omitted. After calculating the fuel adhesion IFMWET in step 234, in step 240, the correction addition amount FAE is calculated according to the following formula.
Calculate.

F A E = 0, 2 ・F A E, Q L
D 10 F M W E T-F M W E T,,
, -(24) Note that FAEOLll is the previously calculated correction addition amount, and FM W ET OLD is the previously calculated amount of fuel attached to the wall surface.

In the above formula (24), the previous correction addition 57 F A E
Since 0L11 is multiplied by 0.2, the previous correction addition amount is attenuated by 80%, and 20% of the previous correction addition amount is reflected in the current correction addition amount. The optimum method for this attenuation is selected depending on the engine, and as mentioned above, it may be attenuated by a predetermined amount at every predetermined crank angle (360° CA in the above example), or it may be attenuated by a predetermined amount at every predetermined time. It may also be attenuated step by step.

In the next step 242, the fuel injection time TAU is calculated using the basic fuel injection time, the correction coefficient FK, and the correction addition amount FAE in the same manner as described above. and step 244
, the correction addition IFAE is the previous correction addition i1 F
At the same time, the fuel adhesion i1FMWET is stored in the RAM as A
It is stored in RAM as TOLn.

In addition, in FIG. 24 above, an example was explained in which the fuel adhesion amount is determined according to the intake pipe pressure when the intake valve is fully closed.
The amount of fuel deposited also changes depending on the engine speed, so the second
As shown in FIG. 5, it may be stored as a map that changes with the intake pipe pressure and engine speed as variables. Further, the amount of fuel adhesion also changes depending on the engine temperature, and the lower the engine temperature, the more the amount of fuel adhesion increases, so the engine temperature may be further determined as a variable. Furthermore, in the above embodiment, an example was explained in which the intake pipe pressure is predicted using a weighted average value, but the intake pipe pressure may also be predicted according to the above 0ω equation, and the intake pipe pressure in a steady state is processed using a first-order lag element. The intake pipe pressure may also be predicted by Further, although the above example describes an example in which the basic fuel injection time is determined based on intake pipe pressure and engine rotational speed when the throttle opening sensor fails, the present invention is not limited to this, and the present invention is not limited to this. The present invention can also be applied to an internal combustion engine in which the amount of intake air is detected by an air flow meter, and the amount of intake air per engine rotation is calculated using this amount of intake air and the engine rotational speed to determine the basic fuel injection time. Furthermore, the above-mentioned second to
The intake pipe pressure prediction method and fuel injection amount correction method in the fourth embodiment can also be applied to fuel injection amount control when the throttle opening sensor is normal.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram for explaining the present invention, FIG. 2 is a diagram for explaining the principle of the first embodiment, and FIG. 3 is a diagram for explaining the principle of the first embodiment.
Fig. 4 is a block diagram for explaining the second embodiment, and Fig. 5 shows the conventional throttle opening and engine rotation speed. Figure 6 is a diagram showing the difference between the intake pipe pressure determined by 7 is a schematic diagram showing an internal combustion engine equipped with a fuel injection amount control device according to an embodiment of the present invention, FIG. 8 is an equivalent circuit diagram of a throttle opening sensor equipped with an idle switch, and FIG. 9 is a diagram showing an equivalent circuit diagram of a throttle opening sensor equipped with an idle switch. FIG. 7 is a block diagram showing details of the control circuit; FIG. 1O is a diagram showing a map of intake pipe pressure in a steady state; FIG. FIG. 12 is a diagram showing a basic fuel injection time map, FIG. 13 is a flowchart showing the main routine of the first embodiment, FIG. 14 is a flowchart showing a routine for calculating the air-fuel ratio feedback correction coefficient FAF, and FIG. 15 16 is a flowchart showing the fuel injection amount calculation routine of the first embodiment of the present invention, FIG. 16 is a flowchart showing the ignition advance angle calculation routine of the above embodiment, and FIGS. 17(1) and (2) show the conventional example and the above. A diagram showing changes in air-fuel ratio and intake pipe pressure with the example,
FIG. 18 is a flowchart showing a routine for calculating the predicted value of intake pipe pressure according to the second embodiment of the present invention, FIG. 19 is a flowchart showing a fuel injection time calculation routine according to the second embodiment, and FIG.
and FIG. 21 are diagrams showing changes in the predicted value of intake pipe pressure, etc. in the second embodiment, and FIG. 22 is a flowchart showing a fuel injection time calculation routine according to the third embodiment of the present invention. FIG. 23 is a diagram showing the relationship between fuel wall adhesion thickness and intake pipe pressure, FIGS. 24 and 25 are diagrams showing a map of the corrected injection amount, and FIG. FIG. 27 is a diagram showing changes in fuel ratio etc. in comparison with the conventional example, and FIG. 27 is a flowchart showing a fuel injection amount calculation routine according to a fourth embodiment of the present invention. 8... Throttle valve, 10... Throttle opening sensor. 4B...Rotation angle sensor.

Claims (1)

[Claims] (1) Throttle opening detection means for detecting the throttle opening, rotation speed detection means for detecting the engine rotation speed, and intake in a steady state based on the detected throttle opening and the detected engine rotation speed. an intake air amount calculation means for calculating the amount of air; a correction means for correcting the response delay of the intake air amount during a transient period with respect to the calculated intake air amount in a steady state; a physical quantity detection means for detecting a physical quantity corresponding to the air amount and other than the throttle opening degree; a failure detection means for detecting whether a failure has occurred in the throttle opening degree detection means; and a failure detection means for detecting whether or not a failure has occurred in the throttle opening degree detection means; control the fuel injection amount based on the intake air amount corrected by the correction means and the detected engine rotational speed when the failure occurs, and also controls the fuel injection amount based on the detected physical quantity when the occurrence of the failure is detected. A fuel injection amount control device for an internal combustion engine, comprising: fuel injection amount control means for controlling the fuel injection amount based on the engine rotation speed.