JPH062597A - Intake air amount detecting device for engine - Google Patents

Abstract

(57) [Abstract] [Purpose] When predicting the actual intake air amount based on the intake air amount measured by the air flow sensor 11, the actual intake air amount may fluctuate due to changes in the acceleration / deceleration state of the engine 1. Even so, the intake air amount can be accurately predicted accordingly. [Configuration] A signal of the intake air amount measured by the air flow sensor 11 is input in a predetermined cycle to calculate a ratio γ between the intake air amount measured this time and the intake air amount measured last time, and the ratio γ is calculated as follows. The intake air amount at the prediction time is predicted by raising the power by the ratio T / T1 of the time T from the time measured this time to the prediction time to obtain the intake air amount and the processing cycle T1 during that period. Change the amount of intake air by 2
Accurately detect the intake air amount by predicting the following curve.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake air amount detecting device for detecting the amount of air taken into an engine, and in particular,
The present invention relates to a device that predicts the intake air amount based on measured values.

[0002]

2. Description of the Related Art Generally, in a fuel injection control system in which fuel is injected and supplied from an injector to control an air-fuel ratio of intake air, an intake air amount is measured at an upstream end of an intake passage by an air flow sensor or the like. The basic injection amount of fuel is set based on the measured intake air amount. If the intake air amount fluctuates while setting the fuel injection amount, the measured intake air amount may not correspond exactly to the filling amount filled in the cylinder. Is not used as it is, but the intake air amount signal is used after being subjected to so-called anneal processing, and at that time, fuel injection time and fuel transportation delay time (fuel injected from the injector enters the cylinder of the engine) It is designed to set the smoothing coefficient smaller than the theoretical smoothing coefficient determined by the engine in consideration of the time required for the process.

However, if the smoothing coefficient is set to a small value in this way, for example, in the rapid acceleration state of the engine, the intake air amount coincides with the actual air charge amount to the engine, and there is no problem, but in the slow acceleration state. Since the intake air amount overshoots, the intake air amount cannot be accurately detected in both the rapid acceleration and the slow acceleration of the engine.

Further, Japanese Patent Publication No. 63-8296 discloses that
It has been proposed to periodically take in the intake air amount measured by a sensor and predict the intake air amount at the time of fuel injection based on the change between the signal value taken in last time and the signal value taken this time. .

[0005]

However, in the above-mentioned conventional proposal example, the change amount of the intake air amount measured in a predetermined cycle is obtained, and this is multiplied by a coefficient to predict the final intake air amount. Therefore, the predicted intake air amount changes linearly, and when the intake air amount changes abruptly, it cannot follow it, and there is a problem that the prediction error is large.

The present invention has been made in view of the above points, and an object thereof is to improve the prediction mode of the intake air amount in the above-mentioned proposed example so that the actual intake air changes due to changes in the acceleration / deceleration state of the engine. Even if the air amount varies, the intake air amount can be accurately predicted accordingly.

[0007]

In order to achieve the above object, in the invention of claim 1, the intake air amount filled in the cylinder of the engine is primary relative to the intake air amount measured by the sensor in the intake passage. Paying attention to the fact that it changes due to the delay, by using this characteristic, the ratio between the intake air amounts measured at predetermined intervals is calculated, and this ratio is raised to the power of the number of processes up to the prediction time, It is designed to predict the intake air amount at.

That is, according to the present invention, as shown in FIG. 1, an air amount measuring means 11 for measuring the amount of air taken into the engine 1 and a signal of the intake air amount measured by the air amount measuring means 11 are provided. The ratio calculation means 33 for calculating the ratio γ of the intake air amount measured this time to the intake air amount measured last time, which is input in a predetermined cycle, and the ratio γ calculated by this ratio calculation device 33 are measured this time. There is provided a predicting means 34 for predicting the intake air amount at the predicted time point by raising the power to the ratio T / T1 of the processing period T1 and the time T from the time point to the predicted time point for predicting the intake air amount. It is characterized by that.

[0009]

With the above construction, in the invention of claim 1, the signal of the intake air amount measured by the air amount measuring means 11 is inputted to the ratio calculating means 33 at a predetermined cycle, and this ratio calculating means 33 measures this time. The ratio γ of the taken intake air amount to the previously measured intake air amount is calculated. Then, in the predicting means 34, the ratio T / T1 of the time T from the time of the current measurement to the time of predicting the intake air amount and the processing cycle T1, that is, the above calculation ratio γ is raised to the power of The intake air amount at the time of prediction is predicted. In this way, raising the ratio γ of the previous and present measured intake air amounts by the number of times of processing indicates that the change of the intake air amount into the cylinder is predicted in a quadratic curve. The intake air amount changes quickly, and when the change in the measured intake air amount is small, the intake air amount changes slowly. As a result, even if the acceleration / deceleration state of the engine 1 changes, the intake air amount can be accurately predicted in accordance with the fluctuation of the actual intake air amount, and the accurate intake air amount can be detected. .

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows the overall configuration of an embodiment of the present invention. Reference numeral 1 denotes a four-cylinder or six-cylinder engine, for example, the engine 1 includes a cylinder block 3 having a plurality of cylinders 2 and a cylinder head assembled to the cylinder block 3. 4, a piston 5 is reciprocally fitted in each cylinder 2, and a combustion chamber 6 is formed surrounded by the piston 5 and the cylinder head 4. The cylinder head 4 has an intake port 8 opened and closed by an intake valve 7 and an exhaust valve 14
And an exhaust port 15 that is opened and closed by.
The intake port 8 constitutes a downstream end portion of an intake passage 9 for supplying intake air to the combustion chamber 6 in the cylinder 2. The intake passage 9 is branched into a plurality for each cylinder 2 on the downstream side of the surge tank 10. In the intake passage 9 on the upstream side of the tank 10, an air flow sensor 11 as an air amount measuring means for measuring the amount of air taken into the engine 1 and a throttle valve 12 for narrowing the intake passage 9 are arranged in this order from the upstream side. An injector 13 for fuel injection is arranged near each intake port 8 in each intake passage 9 on the downstream side of the surge tank 10.

On the other hand, the exhaust port 15 constitutes the upstream end of the exhaust passage 16 for discharging the exhaust gas in the combustion chamber 6, and the oxygen concentration in the exhaust gas is introduced into the exhaust passage 16 in order from the upstream side. An O2 sensor 17 for detecting and a catalyst device 18 for purifying exhaust gas are provided respectively. Reference numeral 19 is an ignition plug for igniting the air-fuel mixture in the combustion chamber 6, and the ignition plug 19 is connected to an ignition coil 21 via a distributor 20.

The injector 13 receives a fuel injection signal from the control unit 31 to control fuel injection, and the control unit 31 outputs an ignition signal to the ignition coil 21. The control unit 31 outputs an intake air amount signal output from the air flow sensor 11, an oxygen concentration signal output from the O2 sensor 17, and a water temperature sensor 32 that detects the cooling water temperature in the cylinder block 3. The water temperature signal and the crank angle signal from the distributor 20 are input, the intake air amount in the cylinder (air filling amount) is calculated based on the intake air amount measured by the air flow sensor 11, and The fuel injection amount is determined based on the intake air amount and the engine speed due to the crank angle change, and the fuel injection signal is output to the injector 13.

That is, the signal processing procedure of the fuel injection control in the control unit 31 will be described.
As shown in FIG. 3, the air flow sensor 1 is preliminarily started at the start.
1 is set, and the measured value g (intake air amount signal) of the air flow sensor 11 is set to the above-mentioned cycle T1 in step S1.
The value is read in 1 and in step S2, the measured value g is subjected to theoretical smoothing processing by the following formula to calculate the cylinder intake air flow rate ge. In other words, the measured value this time is g
(i), when the previous cylinder intake air flow rate is ge (i-1) and the theoretical smoothing coefficient determined by the engine 1 is kg, the current cylinder intake air flow rate ge (i) is ge (i) = Kg * ge (i-1) + (1-kg) * g (i) ...

Thereafter, in step S3, it is determined whether it is time to calculate the cylinder intake air amount Ce. This determination is made by the top dead center cycle of the piston 5 and the injector 13
It is determined whether or not the calculation timing for determining the fuel injection amount comes from the fuel injection timing etc. from N.
When it is O, the process ends.

On the other hand, if the determination is YES, step S
In 4, the ratio γ of the current cylinder intake air flow rate ge (i) calculated in step S2 to the previous cylinder intake air flow rate ge (i-1) is calculated by an equation.

Γ = ge (i) / ge (i-1) ... In the next step S5, the cylinder intake air amount Ce is calculated by an equation. That is, the in-cylinder intake period T is: T = (60 / engine speed) · (1 / n) (where n is the number of intake strokes per revolution of the engine output shaft n = 2, 6 for a 4-cylinder engine) N = for a cylinder engine
3), Ce = (1 + γ ^{T / T1} ) * g (i) * (T / 2) ... The current cylinder intake air flow rate ge (against the previous cylinder intake air flow rate ge (i-1) above. The theory of obtaining the intake air amount Ce in the cylinder by the formula based on the ratio γ of i) will be explained. A difference equation of the formula obtained by the Laplace transform of the formula obtained from the model in which the cylinder 2 of the engine 1 is filled with the intake air. When the intake air flow rate ge in the cylinder has a large time constant for one intake stroke and the opening area of the throttle valve 12 is considered to be small, the above equation is obtained. Then, as shown in FIG. 4, the cylinder intake air flow rate ge (tT) at the predicted time tT
Is ge (tT) = ge (ti) .gamma.T ^{/ T1} where ti is the current measurement time, so the cylinder intake air amount Ce per intake stroke is the cylinder intake air flow rate ge ( The value Ce obtained by integrating t) from the current measurement time ti to the prediction time tT is Ce = ∫ge (t) dt, and the above equation is obtained by approximating this by the trapezoidal rule.

After step S5, the basic injection amount of fuel is determined based on the intake air amount Ce in the cylinder in step S6, and the basic injection amount is determined by the oxygen concentration detected by the O2 sensor 17 and the water temperature sensor. The final injection amount is set by correcting the engine water temperature detected by 32, etc., and the signal of the final injection amount is output to the injector 13 in step S7 to start the fuel injection, and then the process ends.

Therefore, in this embodiment, the above step S
A signal g of the intake air amount measured by the air flow sensor 11 is inputted at 1, S2 and S4 at a predetermined cycle T1, and the previously measured intake air amount ge (i) of the intake air amount ge (i) measured this time is input. i-1) and a ratio calculating means 33 for calculating a ratio γ.

Further, in step S5, the ratio γ calculated by the ratio calculating means 33 is measured from this time to the predicted time to detect the intake air amount, that is, the time to start the fuel injection from the injector 13. The ratio of the time T to the processing cycle T1 (T / T1) is raised to the power, and the cylinder intake air amount Ce (air filling amount) at the time of the above prediction is predicted by the above formula based on the power value. Prediction means 34 is configured.

Therefore, in the above-described embodiment, when the engine 1 is in operation, as shown in FIG.
1 is successively measured, and each measured value g is calculated by the theoretical smoothing coefficient k.
A theoretical smoothing process is performed based on g to calculate the cylinder intake air flow rate ge. Then, at the calculation timing for determining the fuel injection amount based on the top dead center cycle of the piston 5 of the engine 1 or the fuel injection timing from the injector 13, the previous measurement of the intake air amount ge (i) calculated this time is calculated. The ratio γ with the calculated intake air amount ge (i-1) is calculated, and the cylinder intake air amount C
The time T until the prediction time point at which e is to be obtained and the processing cycle T
The intake air amount C in the cylinder at the time of prediction is calculated by an equation having a ratio to 1
e (air charge) is predicted. From the above equation, the ratio γ of the measured intake air amount of the previous time and this time is calculated by the number of processing times (T / T
By raising the power in 1), the change in the intake air amount Ce in the cylinder can be predicted in a quadratic curve. The larger the change in the intake air flow rate ge in the cylinder, the quicker the intake air amount Ce changes. When the change in the air flow rate ge is small, the intake air amount Ce changes slowly. Therefore, even if there is a change in the acceleration / deceleration state of the engine 1 The air amount Ce can be predicted and the intake air amount Ce can be accurately detected.

That is, as shown in FIG. 5B, the throttle valve 12 is opened from the fully closed state to the medium state and the engine 1 is opened.
When the engine is slowly accelerated, the intake air amount is changed to the actual cylinder air one stroke before, as in the case where the throttle valve 12 is fully opened from the fully closed state and the engine 1 is rapidly accelerated as shown in FIG. It is possible to exactly match the filling amount (the conventional example causes an overshoot by adjusting to the rapid acceleration state), and the prediction of the intake air amount is made compatible even when the engine 1 is suddenly accelerated or slowly accelerated. be able to. Also,
As shown in FIG. 5C, the same effect can be obtained even when the engine 1 is decelerated.

Further, the intake air amount g is measured by the air flow sensor 11 at every predetermined cycle T1 and the intake air flow rate ge is calculated by the smoothing process, and the intake air amount g of this time is calculated at the fuel injection amount calculation timing. Since the ratio γ to the previous time is calculated and the intake air amount Ce is predicted based on the calculated ratio γ, it is possible to predict the intake air amount Ce after any time at any time.

[0023]

As described above, according to the first aspect of the present invention, when the intake air amount to be taken into the engine is detected, the intake air amount is measured by the measuring means in the intake passage, and the predetermined period is set. The intake air amount into the cylinder is predicted by calculating the ratio between the measured intake air amounts and multiplying this ratio by the number of processes up to the prediction time to predict the intake air amount into the cylinder at the prediction time. It is possible to predict the change in the air amount as a quadratic curve, and even if there is a change in the acceleration / deceleration state of the engine, etc. The amount of air can be detected.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of the present invention.

FIG. 2 is a diagram showing an overall configuration of an embodiment of the present invention.

FIG. 3 is a flowchart showing a signal processing procedure for fuel injection in the control unit.

FIG. 4 is a characteristic diagram showing a temporal change in a measured value of an air flow sensor and an intake air amount.

FIG. 5 is a characteristic diagram showing a cylinder air charge amount in an engine acceleration / deceleration state in comparison with a predicted intake air amount.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 engine 9 intake passage 11 air flow sensor (air amount measuring means) 13 injector 31 control unit 33 ratio calculating means 34 predicting means

Claims (1)

[Claims] 1. An air amount measuring means for measuring an air amount sucked into an engine, and a signal of the intake air amount measured by the air amount measuring means are input at a predetermined cycle, and the intake air amount measured this time is measured. The ratio calculation means for calculating the ratio with the previously measured intake air amount, the time from the time when the ratio calculated by the ratio calculation device is measured this time to the prediction time at which the intake air amount is predicted, and the processing cycle An intake air amount detection device for an engine, comprising: a prediction unit that predicts the intake air amount at the time of the prediction by raising the power of the intake air amount.