JP2524703B2 - Engine controller - Google Patents

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection engine having a chamber or a surge tank downstream of a throttle valve of an intake system and equipped with an air flow meter, based on intake air amount and engine speed. The present invention relates to an engine control device that controls an amount and an ignition timing.

[Prior art]

Recently, a fuel injection device using an air flow meter is often used in automobile engines.In this case, an air flow meter such as a hot wire type is arranged upstream of the throttle valve to control the air flow rate Qa taken by the engine. A fuel amount that is accurately detected and commensurate with the air flow rate Qa, for example, the fuel amount so that the stoichiometric air-fuel ratio is achieved, that is, the basic fuel injection panel width Tp
The engine speed Ne is calculated by an arithmetic expression such as Tp = K × Qa / Ne (K is a constant), and various corrections are added to the basic fuel injection pulse width Tp to calculate the fuel injection pulse width Ti, and the injector is injected. Fuel is supplied to the engine with extremely high precision by driving only the pulse width Ti. In addition, when controlling the ignition timing as well, the basic fuel injection pulse width Tp is often used as data for load determination in the calculation of the ignition timing. Therefore, the measurement of the intake air amount Qa requires extremely high accuracy. Further, recently, there is a tendency that a hot wire type air flow meter or the like having high responsiveness as a sensor is also used for the air flow meter. However, the air flow meter is arranged only upstream of the throttle valve, and does not directly measure the amount of air taken into the engine. For example, when the throttle valve is changed from closed to open, the amount of air flowing into the engine increases, and at the same time, the pressure in the chamber downstream of the throttle valve and the suction pipe also increases.
The amount of air required for this pressure increase is also measured by the air flow meter. In other words, the air flow meter on the upstream side of the throttle valve measures an air amount exceeding the air amount flowing into the engine for a moment, when the throttle valve is closed and then opened. This appears as a spike-like overshoot of the air flow rate, and the amount thereof is larger as the volume of the chamber downstream of the throttle valve and the intake manifold is larger, and is larger as the sensor having good response such as a hot wire type air flow meter. On the other hand, the injection (fuel injection valve) is on the downstream side of the intake manifold in MPI (multipoint injection), so if the fuel is injected according to the measured air amount, it will be more than necessary for the air flowing into the engine. Fuel is supplied, the air-fuel ratio A / F is rapidly enriched, and CO and HC in the exhaust gas increase. Further, in a severe case, there is a problem that the engine output is reduced due to overrich and the driving feeling is deteriorated. Further, in the case of an engine control device that controls the ignition timing as well, a momentary retardation of the ignition timing may be considered, which also causes a reduction in engine output and deterioration of exhaust emission. In addition, when the throttle valve is opened → closed, the air-fuel ratio
Problems such as A / F, ignition timing and deviation from the optimum value occur. To cope with this, for example, in Japanese Patent Laid-Open No. 57-73831, the movement of the throttle valve is detected and the basic fuel injection pulse width Tp calculated based on the output of the hot wire type air flow meter is corrected. A technology that solves the problem of engine malfunction due to a change in the proper air-fuel ratio due to a sudden change in throttle opening, improves responsiveness during acceleration, and prevents misfires and rattling during deceleration. Is disclosed. Further, in JP-A-59-170428, the basic fuel injection amount calculated from the intake air amount and the engine speed is increased / decreased based on the change amount of the signal voltage from the hot wire type air flow meter with respect to time, A technique for obtaining the same effect as that of the above-mentioned prior art is disclosed.

[Problems to be Solved by the Invention]

However, in each of the preceding examples, a problem caused by a change in the proper air-fuel ratio due to a sudden change in the opening of the throttle valve, such as the movement of the throttle valve and the change amount of the signal voltage from the hot wire type air flow meter with respect to time Since the detection error of the intake air amount to the engine that occurs at the time of transition is indirectly estimated and corrected, it is not possible to accurately follow the change in the intake system state. However, there is a disadvantage that the air-fuel ratio cannot be sufficiently maintained at an appropriate value. In view of the above circumstances, the present invention reduces the measurement error of the intake air amount caused by the capacity of the chamber downstream of the throttle valve and the intake manifold, which occurs when the throttle valve is suddenly opened and closed.
An object of the present invention is to provide an engine control device capable of measuring a more accurate intake air amount and maintaining at least one of an optimum fuel injection amount and an optimum ignition timing.

[Means for Solving the Problems]

In order to achieve the above object, the present invention provides a throttle portion resistance calculation means for calculating the resistance of the throttle portion with respect to intake air based on the throttle opening, and an engine portion resistance for calculating engine resistance with respect to intake air based on the engine speed. Calculating means, and an intake system time constant calculating means for calculating a time constant with respect to the pressure in the intake pipe downstream of the throttle valve based on the throttle resistance, the engine resistance, and the preset volume of the intake system downstream of the throttle valve. An intake pipe internal pressure calculating means for calculating the intake pipe internal pressure downstream of the throttle valve in a steady state based on the throttle portion resistance, the engine portion resistance, and the intake side pressure upstream of the throttle valve, and the intake pipe internal pressure in the steady state above A first-order lag processing means that performs a first-order lag processing with a constant, and a switch according to the change in throttle opening The filling amount of air filled in liters valve downstream of the intake system, the intake system volume downstream the throttle valve,
And an engine which corrects the measured intake air amount measured by an air flow meter installed on the upstream side of the throttle valve and the filled air amount calculation means which is calculated based on the fluctuation rate of the pressure in the intake pipe after the first-order lag processing. A real engine intake air amount calculating means for calculating the actual engine intake air amount actually inhaled into the engine, and a fuel injection amount calculation for calculating the fuel injection amount and the ignition timing based on the actual engine intake air amount and the engine speed, respectively. And at least one of ignition timing calculation means.

[Action]

In the present invention, the dynamic characteristics of air in the intake pipe are grasped in advance and stored in the memory in the control device as a model,
Calculate the throttle resistance and engine resistance to intake air based on the throttle opening and engine speed,
Based on these throttle resistance, engine resistance, and preset volume of the intake system downstream of the throttle valve, a time constant for the pressure in the intake pipe downstream of the throttle valve is calculated, and the throttle resistance, engine resistance,
And the intake pipe internal pressure downstream of the throttle valve in a steady state is estimated based on the intake side pressure upstream of the throttle valve, and the intake pipe internal pressure is subjected to a first-order lag processing by the time constant, and the intake air downstream of the throttle valve is changed according to the change in throttle opening. The amount of air filled in the system is calculated based on the intake system volume downstream of the throttle valve and the rate of change of the intake pipe internal pressure after the primary delay process. Then, the measured intake air amount measured by the aerometer installed upstream of the throttle valve is corrected by the above-mentioned filling air amount to estimate the actual engine intake air amount actually sucked into the engine. The fuel injection amount is calculated based on the amount and the engine speed to determine the ignition timing.

【Example】

1 to 7 are views showing an embodiment of the present invention. FIG. 1 is a system diagram of an engine control device, and FIG. 2 is a model of an engine intake system and an equivalent model replaced with an electric circuit. FIG. 3 is a model diagram showing the functional configuration of the engine control device, FIG. 4 is an explanatory view showing the setting of the throttle resistance R1 with respect to the throttle opening, and FIG. 5 is the setting of the engine resistance R2 with respect to the engine speed. FIG. 6 is a flow chart showing a processing procedure in the engine control device, and FIG. 7 is a time chart showing changes in each data during transition. In FIG. 1, reference numeral 1 is an engine, 2 is an intake pipe including a manifold, 3 is a chamber downstream of a throttle valve, 4 is a throttle valve, 5 is an injector (fuel injection valve), 6 is an ignition coil, 10 is a hot wire type, etc. Is an air flow meter, 11 is a throttle opening sensor, 12 is a water temperature sensor, 13 is a crank angle sensor, 14 is an oxygen sensor, and 20 is an engine control device including a microcomputer. In such a system, the engine control device 20
Intake air amount Qa measured by the air flow meter 10
And the engine speed Ne obtained from the signal from the crank angle sensor 13, the basic fuel injection amount, that is, the basic fuel injection pulse width is calculated by Tp = K × Qa / Ne (K is a constant), Correction such as the cooling water temperature detected by the water temperature sensor 12 is added to the fuel injection pulse width Tp,
Further, the fuel injection pulse width Ti is obtained by performing feedback correction based on the output from the oxygen sensor 14, and the injector 5 is driven with the fuel injection pulse width Ti to obtain, for example, the theoretical air-fuel ratio A / F corresponding to the intake air amount Qa. Inject an amount of fuel like this. Also, the measured intake air amount Qa and engine speed
The optimum ignition timing corresponding to Ne is determined by a map search or the like, and ignition is performed via the ignition coil 6. In this control system, during a transition due to opening / closing of the throttle valve 4, a spike-like overshoot or undershoot occurs in the measured intake air amount Qa due to the capacity C of the chamber 3 and the intake pipe 2 downstream of the throttle valve. The air flow meter 10 measures a value different from the air amount Qe actually taken into the engine 1. In order to perform this correction, the engine control device 20 stores a model of the dynamic characteristics of the intake system as shown in FIG. In the model of the intake system shown in FIG. 2A, the intake side pressure Po (atmospheric pressure) is set to the power supply voltage Vo, the intake air amount Qa measured by the air flow meter 10 is set to the current value I, and the throttle valve 4 is set. The flow path resistance of the throttle portion according to the opening is a variable resistance RI, the engine resistance according to the engine speed is a variable resistance R2, the volume of the chamber 3 and the intake pipe 2 downstream of the throttle valve is a condenser capacity C, The amount of air Qc that fills the volume of the chamber 3 and the intake pipe 2 downstream of the throttle valve at a transient time is the current value Ic, the amount of inflow air Qe flowing into the engine 1 is the current value Ie, and the pressure in the intake pipe 2 is By replacing P with voltage V, an approximation is made as an equivalent model as shown in FIG. In this equivalent model, the transient response of the voltage V after the variable resistor R1 to the stepwise input of the input voltage Vo is Is represented by Here, the throttle resistance R1 is an approximate value represented by (Po-P) / Qa according to the throttle opening θ and has a value as shown in FIG. It is stored in. Also,
The engine resistance R2 is a value represented by P / Qe according to the engine speed Ne and has a value as shown in FIG. 5, and is stored in a memory of a table having the engine speed Ne as a grid. In this way, the voltage V, that is, the intake pipe pressure P can be approximated as a first-order lag system with a time constant τ = C · R1 · R2 / (R1 + R2). Therefore, the throttle resistance R1 is a function determined by the throttle opening θ. Engine resistance R2 to engine speed Ne
As a function of the suction side pressure Po, and the volume C in the chamber 3 and the intake pipe 2 downstream of the throttle valve as constants,
If each is stored in a memory and a first-order delay processing means is provided in the engine control device 20, the intake pipe internal pressure P can be estimated. Then, the pressure P in the intake pipe is differentiated with time to calculate the fluctuation rate of the pressure in the intake pipe downstream of the throttle valve.
The amount Qc of air charged into the chamber 3 and the intake pipe 2 downstream of the throttle valve at the time of transition can be calculated by C · dp / dt, and the actual amount Qe of intake air of the engine 1 is obtained by Qa-Qc, which occurs at the time of transition. It becomes possible to accurately determine the fuel injection amount and the ignition timing without being affected by the overshoot or undershoot of the measured intake air amount Qa. The above arithmetic processing is realized by each functional means in the engine control device 20, as shown in FIG. In the figure, reference numeral 21 is an engine speed calculating means, which determines the engine speed Ne based on a signal from the crank angle sensor 13. Reference numeral 22 is a measurement intake air amount calculation means, which receives the voltage signal from the hot wire type air flow meter 10
Convert to. Reference numeral 23 is a throttle resistance table that stores the throttle resistance R1 as a throttle opening θ, 24 is an engine resistance table that stores the engine resistance R2 as an engine speed Ne, and 25 is a throttle valve. A memory in which the capacity C of the downstream chamber 3 and the intake pipe 2 and the suction side pressure Po (approximately atmospheric pressure) are stored in advance, 26
Is a throttle resistance calculation means, 27 is an engine resistance calculation means, 28 is an intake system time constant calculation means, 29 is an intake pipe internal pressure calculation means for calculating the intake pipe internal pressure P _B in a steady state, 30
Is a first-order lag processing means for performing a first-order lag processing on the intake pipe internal pressure P _B to obtain the intake pipe internal pressure P (t) during a transition, 31 is a filling air amount calculating means, 32 is an actual engine intake air amount calculating means,
33 is a fuel injection amount calculation means, and 34 is an ignition timing calculation means. Next, the operation of the engine control device 20 configured as described above will be described with reference to the flowchart of FIG. 6 and the time chart of FIG. The engine control device 20 converts the voltage signal from the air flow meter 10 into the measured intake air amount Qa in the measured intake air amount calculating means 22 (step S101), and the throttle valve 4 stepwise, for example, as shown in FIG. 7 (a). When opened like
A signal Qa with spike-like overshoot as shown in FIG. 7B is output. Then, the throttle opening signal θ is input from the throttle opening sensor 11 and the engine speed Ne is input from the engine speed calculating means 21 (step S1
02), the throttle resistance calculation means 26 reads the preset throttle resistance R1 from the throttle resistance table 23 using the throttle opening θ as an address signal, and
The engine resistance calculating means 27 reads the preset engine resistance R2 from the engine resistance table 24 using the engine speed signal Ne as an address signal (step S1).
03). Next, the intake system time constant calculating means 28 calculates the first-order lag time constant τ of the intake system from the read throttle resistance R1 and engine resistance R2 and the capacitance C stored in the memory 25 ( Step S104). Further, the intake pipe internal pressure calculation means 29 calculates the intake pipe internal pressure P _B in the steady state by the resistances R1 and R2 and the intake side pressure Po stored in the memory 25 (step S105). 1 to the pressure P _B by the time constant τ in the first-order lag processing means 30.
Next-delay processing is performed for each calculation cycle Δt to obtain the intake pipe internal pressure P (t) during the transition (step S106), FIG. 7 (d).
The intake pipe internal pressure P is estimated as shown in. Next, the filling air amount calculating means 31 determines the time differential value dp / d of the estimated intake pipe pressure P.
t, that is, the rate of change of the pressure in the intake pipe downstream of the throttle valve and the capacity C, the amount of air Qc to be filled in the chamber 3 and the intake pipe 2 downstream of the throttle valve at the transition is determined (step S107), and FIG. Estimate as in (e). Based on the estimated air amount Qc and the measured intake air amount Qa obtained by the measured intake air amount calculating means 22, the actual engine intake air amount calculating means 32 calculates the air amount Qe actually sucked into the engine 1. (Step S108), the actual engine intake air amount Qe is estimated as shown in FIG. 7 (f). In the actual engine intake air amount Qe thus obtained, there is no spike-like overshoot like the measured intake air amount Qa, and by this and the engine speed Ne, the fuel injection amount in the fuel injection amount calculation means 33, That is, the basic fuel injection pulse width Tp is
= K × Qa / Ne (K is a constant), and various corrections are added to this basic fuel injection pulse width Tp
Is calculated (step S109), and FIG.
The air-fuel ratio A / F as shown in Fig. 7 is obtained, and a large fluctuation of the air-fuel ratio A / F as in the conventional example shown in Fig. 7 (c) does not occur. Further, the ignition timing calculation means 34 also obtains the optimum ignition timing by a map search or the like based on the actual engine intake air amount Qe corresponding to the actual load and the engine speed Ne (step S110). The required retardation does not occur. In the above example, the transient time when the throttle valve is suddenly opened has been described.However, the same operation is performed during the transient time when the throttle valve is rapidly closed to suppress the fluctuation of the air-fuel ratio A / F to the lean side, and the ignition timing. It is possible to prevent inconvenience due to deviation from the optimum value of.

【The invention's effect】

As is clear from the above description, the engine control device of the present invention estimates the intake pipe internal pressure in consideration of the capacity of the chamber downstream of the throttle valve and the intake pipe, and further determines the air amount actually taken into the engine. Since I tried to estimate
Even during transients such as opening and closing of the throttle valve, the effects of overshoot and undershoot of the measured intake air amount due to these capacities are eliminated, and the deviation from the set value of the air-fuel ratio is minimized to reduce exhaust gas. It is possible to prevent the generation of CO and HC inside. In addition, it is possible to stabilize the output and improve the driving feeling. Further, there is an effect that the deviation of the ignition timing from the proper value can be suppressed to the minimum, and the feeling of operation and the exhaust emission can be improved.

[Brief description of drawings]

1 to 7 show an embodiment of the present invention.
FIG. 2 is a system diagram of the engine control device, FIG. 2 is a model diagram showing a model (a) of an engine intake system and an equivalent model (b) replaced with an electric circuit, and FIG. 3 is a functional configuration diagram of the engine control device. FIG. 4 is an explanatory diagram showing the setting of the throttle resistance R1 with respect to the throttle opening, FIG. 5 is an explanatory diagram showing the setting of the engine resistance R2 with respect to the engine speed, and FIG. 6 is a processing procedure in the engine control device. The flowchart and FIGS. 7 (a) to 7 (g) are time charts showing changes in each data during the transition. 1 ... Engine, 2 ... Intake pipe, 3 ... Throttle valve downstream chamber, 4 ... Throttle valve, 5 ... Injector, 10 ... Air flow meter, 11 ... Throttle opening sensor, 13 ... Crank angle sensor, 20 ... Engine control device, 23 ... Throttle section resistance table, 24 ... Engine section resistance table, 25 ... Memory, 26 ... Throttle section resistance calculating means, 27 ... Engine section resistance calculating means, 28 ... Intake system time constant calculating means, 29 ... Intake pipe pressure calculating means , 30 ... Primary delay processing means, 31 ... Filled air amount calculation means, 32 ... Actual engine intake air amount calculation means, 33 ...
Fuel injection amount calculation means, 34 ... Ignition timing calculation means.

Claims (1)

(57) [Claims] 1. A throttle resistance calculation means for calculating a resistance of a throttle portion with respect to intake air based on a throttle opening, an engine resistance calculation means for calculating an engine resistance with respect to intake air based on an engine speed, and the throttle. An intake system time constant calculating means for calculating a time constant with respect to a pressure in the intake pipe downstream of the throttle valve based on the resistance of the engine, the resistance of the engine, and the volume of the intake system downstream of the throttle valve that has been previously resisted; Intake pipe internal pressure calculating means for calculating the intake pipe internal pressure downstream of the throttle valve in the steady state based on the engine resistance and the intake side pressure upstream of the throttle valve, and the intake pipe internal pressure in the steady state is subjected to first-order lag processing by the time constant. First-order lag processing means and suction valve downstream of the throttle valve in response to changes in throttle opening. A filling air amount calculating means for calculating the amount of filling air to be filled into the system based on the intake system volume downstream of the throttle valve and the rate of fluctuation of the pressure in the intake pipe after the first-order lag processing, and an air flow installed upstream of the throttle valve. An actual engine intake air amount calculating means for correcting the measured intake air amount measured by the meter with the filling air amount to calculate the actual engine intake air amount actually sucked into the engine; and the actual engine intake air amount and the engine. An engine control device comprising: at least one of a fuel injection amount calculation means for calculating a fuel injection amount and an ignition timing based on the rotational speed, and an ignition timing calculation means.