JP4025977B2 - Engine intake air amount calculation device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an engine intake air amount calculation device that predicts changes in the intake air amount and intake pressure (hereinafter collectively referred to as intake air correlation amount) of an engine during a transient operation or the like.
[0002]
[Related background]
In an intake pipe injection type gasoline engine, fuel injection is performed in an intake stroke or an exhaust stroke. Therefore, the fuel injection amount is determined based on the intake amount before being actually sucked into the cylinder (for example, several strokes before). There must be. Even in the case of the in-cylinder injection type, in the case of uniform premix combustion, fuel is injected during the intake stroke, so the injection amount must be determined based on the intake amount until the start of the intake stroke. Therefore, when a transition is made from steady running or decelerating running to a transient operation state such as acceleration, the fuel injection amount is determined based on the intake amount before acceleration at the beginning of the transition, so the actual intake air drawn into the cylinder There is a risk that the amount of fuel will be insufficient with respect to the amount, resulting in a temporary lean state, and in some cases misacceleration or unstable combustion will cause an acceleration failure and deteriorate drivability.
[0003]
Focusing on the above problem, the fuel injection amount is increased in accordance with the change in the throttle opening, or the intake air amount is reduced based on the change in the throttle opening as in the technique described in Japanese Patent Publication No. 2-51052. Measures to correct it have been implemented. However, since all the measures only correct the fuel injection amount and the intake air amount in accordance with the amount of change in the throttle opening, if the operating state changes, it is predicted from the actual intake air amount and the amount of change in the throttle opening. There was a problem that the inhaled air intake did not match. That is, even if the amount of change in the throttle opening is the same, if the manifold pressure or the throttle opening position before the change is different, the change in the intake amount will also be different, resulting in a prediction error in the intake amount. It is.
[0004]
Therefore, for example, in the technique described in Japanese Patent Publication No. 8-14262, if the intake air flow velocity passing through the throttle is different, the increase state of the intake air amount when the throttle opening is increased is different, A correction coefficient is calculated based on the pressure ratio before and after the throttle, and the fuel injection amount during transient operation is corrected based on the correction coefficient and the amount of change in throttle opening.
[0005]
[Problems to be solved by the invention]
That is, the technique described in the above publication can predict an intake air amount that is closer to reality by simulating the correlation of the intake air amount change with respect to a change in throttle opening. However, this technology does not take into account the error included in the throttle opening itself, that is, the difference between the throttle opening detected by the sensor and the actual effective opening area of the throttle. That is, according to the research of the present inventor, it is confirmed that the intake air amount predicted from the throttle opening and the front / rear differential pressure varies when the throttle front / rear differential pressure is different even at the same throttle opening. . This phenomenon is presumed to be due to the fact that turbulent flow is formed by separation of intake air at the edge of the throttle valve, affecting the effective opening area of the throttle, and because of the change in the adiabatic index due to heat transfer. In the technique described in the gazette, since the countermeasure for this point is not taken, the prediction error of the intake air amount still cannot be solved.
[0007]
Accordingly, an object of the invention of claim 1 is an intake air of an engine capable of calculating the intake air amount passing through the throttle with high accuracy based on the effective opening area in consideration of the influence of the turbulent flow generated at the edge portion of the throttle. The object is to provide a quantity calculation device.
The object of the invention of claim 2 is to calculate the intake air amount passing through the throttle with high accuracy on the basis of the effective opening area in consideration of the influence of the turbulent flow generated at the edge portion of the throttle, and by using the calculated intake air amount. Accordingly, an object of the present invention is to provide an engine intake air amount calculation device capable of accurately predicting an intake air correlation amount after a predetermined number of strokes.
[0009]
[Means for Solving the Problems]
To achieve the above object, a first aspect of the invention, the throttle opening area and the throttle opening detection means, the output of throttling opening detection means for detecting or estimating a throttle opening arranged in the intake pipe of the engine An opening area calculating means for calculating the intake pressure, an intake pressure estimating means for estimating the intake pressure downstream of the throttle based on the output of the throttle opening detecting means, an atmospheric pressure detecting means for detecting or estimating the atmospheric pressure, and an intake pressure estimating means Effective opening area calculating means for calculating the throttle effective opening area by correcting the throttle opening area according to the output of the engine and the output of the atmospheric pressure detecting means, and the output of the intake pressure estimating means and the output of the atmospheric pressure detecting means based calculates the intake air flow rate, the passage intake air amount calculating means for calculating an amount of intake air passing through the throttle on the basis of the calculation result of the intake flow rate and the effective opening area calculation means Those were example.
[0010]
Accordingly, the opening area of the throttle is calculated based on the throttle opening, and the effective opening area is calculated by correcting the throttle opening area according to the intake pressure and the atmospheric pressure on the downstream side of the throttle estimated from the throttle opening. In addition, the amount of air passing through the throttle is calculated based on the effective opening area and the intake air flow velocity obtained from the intake pressure and the atmospheric pressure .
The intake air passing through the throttle forms a turbulent flow at the throttle edge, and even if the throttle opening area is the same, the effective opening area is different if the turbulent flow generation state is different. The state of turbulent flow changes according to the intake air flow velocity passing through the throttle, and the intake air flow velocity correlates with the front-rear pressure of the throttle. Therefore, if the throttle opening area is corrected based on the front-rear pressure, a substantial effective opening area is obtained. It is possible to calculate, and based on this effective opening area, an accurate throttle passing air amount is calculated, and various controls can be appropriately performed.
[0011]
According to a second aspect of the present invention, in the first aspect, the intake correlation amount detecting means for detecting or estimating the intake correlation amount correlated with the intake state from the throttle, and the smoothing means for smoothing the output of the intake correlation amount detecting means, And an intake correlation amount prediction means for predicting an intake correlation amount after a predetermined number of strokes based on an output of the smoothing means based on a change amount of the intake pressure estimated by the intake pressure estimation means in a predetermined period. is there.
[0012]
Therefore, the intake correlation amount that correlates with the intake state from the throttle, specifically, the intake pressure, the intake amount, etc. is detected or estimated and smoothed, and is estimated from the throttle opening on the basis of the smoothed intake correlation amount. The intake correlation amount after a predetermined number of strokes is predicted based on the amount of change in intake pressure with high responsiveness over a predetermined period .
Since the calculation process of the throttle passage air amount is exactly the same as that of the first aspect, the redundant description is omitted, but based on the effective opening area in consideration of the turbulent flow generation state at the throttle edge portion. Since an accurate throttle passing air amount is calculated, the intake correlation amount after a predetermined number of strokes can be accurately predicted as a result.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of an intake air amount calculation apparatus for an engine embodying the present invention will be described. The engine of this embodiment employs a so-called speed-density method that controls fuel injection based on the manifold pressure, and the intake air amount calculation device predicts the manifold pressure after a predetermined number of strokes as the intake air correlation amount. .
[0017]
FIG. 1 is an overall configuration diagram showing an intake air amount calculation device for an engine according to the present embodiment. The engine 1 is configured as an intake pipe injection type four-cycle gasoline engine. The intake system of the engine 1 includes an intake manifold 2, a surge tank 3 and an intake passage 4. The intake air introduced into the intake passage 4 via the air cleaner 5 is adjusted in flow rate by the throttle valve 6 and then taken through the surge tank 3. It is distributed to each cylinder by the manifold 2, mixed with the fuel injected from the fuel injection valve 7, and sucked into the cylinder of each cylinder from the intake port 8.
[0018]
The exhaust system of the engine 1 includes an exhaust passage 9, a catalyst, a silencer, and the like (not shown). The exhaust gas after being ignited by a spark plug 10 is discharged from the exhaust port 11 through the exhaust passage 9.
On the other hand, an input / output device (not shown), a storage device (ROM, RAM, etc.) used for storage of a control program, a control map, etc., a central processing unit (CPU), a timer counter, etc. Control unit) 21 is installed. On the input side of the ECU 21, an accelerator sensor 22 that detects the accelerator operation amount APS, a vehicle speed sensor 23 that detects the vehicle speed V, a throttle sensor 24 (throttle opening detection means) that detects the throttle opening TPS, and an atmospheric pressure P0 are detected. An atmospheric pressure sensor 25 (front / rear pressure detecting means), a manifold pressure sensor 26 (front / rear pressure detecting means, intake correlation amount detecting means) for detecting the manifold pressure Ps, and a crank angle sensor for outputting a crank angle signal as the engine rotates. Various sensors such as 27 are connected, and various devices such as a step motor 28 for opening and closing the fuel injection valve 7, the spark plug 10, and the throttle valve 6 are connected on the output side.
[0019]
The ECU 21 controls the ignition timing of the spark plug 10 based on, for example, the engine rotational speed Ne and the manifold pressure Ps obtained from the crank angle signal, while the target throttle opening TPSobj obtained from the accelerator operation amount APS, the vehicle speed V, and the like. Based on the actual throttle opening TPS, the step motor 28 controls the opening of the throttle valve 6. On the other hand, the ECU 21 controls the injection amount of the fuel injection valve 7 based on the fuel injection amount calculated from the manifold pressure Ps. Hereinafter, details of this fuel injection control will be described.
[0020]
The ECU 21 executes the manifold pressure estimation routine shown in FIG. 2 every 5 msec. First, in step S2, the throttle opening TPS detected by the throttle sensor 24, the atmospheric pressure P0 detected by the atmospheric pressure sensor 25, and the manifold pressure sensor 26 are detected. The sensor detection value such as the manifold pressure Ps detected by the above is read. Next, in step S4, the current manifold pressure Ps is integrated (Sp = Sp + Ps), and the averaging counter C is incremented (C = C + 1). In the following step S6, the basic opening area S0 of the throttle valve 6 is calculated from the following equation (0) (opening area calculating means), and in step S8, the effective opening area S of the throttle valve 6 is calculated from the following equation (1) (effective). Area calculation means).
[0021]
S0 = f [TPS] (0)
S = (1 + aX) × S0 (1)
Here, a is a predetermined correction constant, and X is a pressure ratio Pm (n) / P0 between the atmospheric pressure P0 and the estimated manifold pressure Pm (n), which is obtained in step S20 described later.
In subsequent step S10, the intake air flow velocity U is calculated from the following equation (2), and in step S12, the throttle passage intake air amount Qth is calculated from the following equation (3) (passage air amount calculating means).
[0022]
U = f [X] ……… (2)
Qth = S × U ……… (3)
Further, in step S14, the current estimated manifold pressure Pm (n) is calculated from the following equation (4), and the estimated manifold pressure Pm (n) is set to the previous value Pm (n-1).
Pm (n) = Pm (n-1) + (Qth-Qe) / Vm (4)
Here, Vm is the intake pipe volume, and Qe is the estimated intake air amount sucked into the cylinder, which is obtained in step S22 described later.
[0023]
Thereafter, in step S16, it is determined whether or not the estimated manifold pressure Pm (n) is equal to or greater than the value obtained by multiplying the atmospheric pressure P0 by 0.98. If NO (No), the process proceeds to step S20. If the determination is YES (affirmative), the estimated manifold pressure Pm (n) is set to a value obtained by multiplying the atmospheric pressure P0 by 0.98 in step S18, and the process proceeds to step S20.
In step S20, the pressure ratio X is calculated from the following equation (5), and in the subsequent step S22, the in-cylinder intake estimated intake air amount Qe is calculated from the following equation (6) (combustion chamber intake air amount calculating means).
[0024]
X = Pm (n) / P0 (5)
Qe = K [Ne] × Pm (n) × Vc (6)
Here, K [Ne] is a volumetric efficiency coefficient, and Vc is a cylinder volume. In step S24, a delay estimated manifold pressure Psa having a predetermined delay with respect to the estimated manifold pressure Pm (n) is calculated from the following equation (7), and then the routine is terminated.
[0025]
Psa = K × Psa + (1−K) × Pm (n) (7)
Here, K is a delay correction coefficient.
On the other hand, the ECU 21 executes the injection amount setting routine shown in FIG. 3 at the timing (BTDC 5 ° CA) when the SGT signal is input from the crank angle sensor 27. First, in step S32, the manifold pressure average value Psave (= Sp / C) for one stroke is obtained, the integrated value Sp of the manifold pressure Ps is cleared, and the averaging counter C is cleared.
[0026]
In the subsequent step S34, the delay estimated manifold pressure average value Psave 'for one stroke is calculated from the following equation (8), and the delay estimated manifold pressure Psa is set to the previous value Psaold.
Psave '= (Psa + Psaold) / 2 ……… (8)
In step S36, the estimated manifold pressure deviation dP is calculated from the following equation (9).
dP = Pm (n) −Pm (n−1) (9)
In the subsequent step S38, it is determined whether or not the difference ΔTPS between the target throttle opening TPSobj set in the throttle opening control and the actual throttle opening TPS is equal to or greater than a predetermined value ΔTPS0 on the positive side. When the determination is NO, the prediction gain Kgain is set to 1.0 in step S40, and then the process proceeds to step S44. Further, for example, when the target throttle opening TPSobj suddenly increases with the accelerator operation as in the early stage of acceleration, the difference ΔTPS rapidly increases to the positive side, and the determination in step S38 becomes YES. In this case, the ECU 21 determines the predicted gain Kgain in step S40. Is set to 2.0, and then the process proceeds to step S44.
[0027]
In step S44, the pressure change amount ΔP between two strokes is calculated from the following equation (10), and in step S46, the sensor response delay amount ΔPs is calculated from the following equation (11).
ΔP = Kgain × dP (n) × 2 · Tsgt / 5 (10)
ΔPs = Pm (n) −Psave ′ (11)
Here, Tsgt is a required time for one stroke.
[0028]
Further, in step S48, it is determined whether or not the estimated manifold pressure Pm (n) is equal to or greater than a predetermined value Pm0. If NO, the corrected manifold pressure P (n) is calculated from the following equation (12) in step S50 (intake correlation amount). Prediction means).
P (n) = Psave + ΔP + ΔPs (12)
When the determination in step S48 is YES, the manifold pressure average value Psave is set as the corrected manifold pressure P (n) in step S52. Thereafter, the fuel injection amount Qinj is calculated from the following equation (13) in step S54, and then the routine is terminated.
[0029]
Qinj = Kinj × K (Ne) × P (n) ……… (13)
Here, Kinj is a coefficient for converting the corrected manifold pressure P (n) into a fuel amount.
Under the control of the ECU 21, the corrected manifold pressure Pm (n) is predicted as follows.
FIG. 4 is a time chart showing a change state of each measured value and estimated value when the throttle valve 6 is suddenly opened. An injection amount setting routine is executed by the ECU 21 for each stroke of the engine shown on the horizontal axis. On the other hand, a plurality of manifold pressure estimation routines are executed between each stroke.
[0030]
The manifold pressure Ps detected by the manifold pressure sensor 26 fluctuates in synchronization with the stroke of the engine, rapidly increases with the throttle opening TPS, and corresponds to an engine intake delay 2 on a virtual line obtained by smoothing the manifold pressure Ps. It is ideal to obtain a post-stroke value (corresponding to the corrected manifold pressure P (n) in the figure) and apply the value to the setting of the fuel injection amount Qinj.
[0031]
On the other hand, as a filter process for smoothing the manifold pressure Ps, the manifold pressure average value Psave is calculated for each stroke based on the integrated value Sp of the manifold pressure Ps every 5 msec. The average value Psave inevitably follows the manifold pressure Ps with a predetermined delay.
On the other hand, the estimated manifold pressure Pm (n) is calculated every 5 msec based on the throttle passage intake air amount Qth obtained from the effective opening area S of the throttle valve 6, and the sensor delay characteristic with respect to the estimated manifold pressure Pm (n). A delay estimated manifold pressure Psa having a delay simulating the above is calculated, and a delay estimated manifold pressure average value Psave ′ is calculated for each stroke based on the delay estimated manifold pressure Psa. Then, a pressure change amount ΔP corresponding to two strokes is calculated from the estimated manifold pressure deviation dP for 5 msec, and a sensor response delay amount ΔPs corresponding to the sensor delay is calculated, and the pressure based on the manifold pressure average value Psave is calculated. A value after elapse of the change amount ΔP and the sensor response delay amount ΔPs is predicted as the corrected manifold pressure P (n) and applied to the setting of the fuel injection amount Qinj.
[0032]
That is, after correction in consideration of not only the pressure change amount ΔP for two strokes based on the highly responsive estimated manifold pressure Pm (n) obtained from the throttle opening TPS, but also the sensor response delay amount ΔPs corresponding to the sensor delay. Manifold pressure P (n) is predicted to improve the response of fuel injection control during transient operation.
In this embodiment, the basic opening area S0 of the throttle valve 6 is corrected by the pressure ratio Pm (n) / P0 before and after the throttle, and the throttle passage intake air amount Qth is calculated based on the obtained effective opening area S. Yes. That is, as shown in the test results of FIG. 5, the characteristic of the effective opening area S with respect to the throttle opening TPS is affected by the throttle front-rear differential pressure. The effective opening area S is significantly different between the differential pressure of 100 mmHg and 500 mmHg. According to the study by the present inventor, this phenomenon is presumed to be due to the fact that turbulent flow is formed by the separation of the intake air at the edge portion of the throttle valve 6 and affects the effective opening area S0.
[0033]
The turbulent flow at this time is generated according to the intake flow velocity U passing through the throttle valve 6, and the intake flow velocity U correlates with the pressure ratio Pm (n) / P0 before and after the throttle, so the pressure ratio Pm (n) The effective effective opening area S is obtained using / P0. Therefore, it is possible to always calculate an accurate throttle passage intake air amount Qth based on the effective opening area S, and thus to accurately predict the corrected manifold pressure P (n) and set an appropriate fuel injection amount Qinj. Accordingly, it is possible to avoid problems such as acceleration failure caused by an inappropriate amount of fuel and to realize extremely good drivability.
[0034]
On the other hand, when the estimated manifold pressure Pm (n) is not less than the value obtained by multiplying the atmospheric pressure P0 by 0.98 in step S16, the estimated manifold pressure Pm (n) is limited to the value obtained by multiplying the atmospheric pressure P0 by 0.98. In spite of this processing, if it is determined in step S48 that the estimated manifold pressure Pm (n) is equal to or greater than the predetermined value Pm0, the corrected manifold pressure P (n) is not predicted in step S50, but in step S52. The manifold pressure average value Psave is set as the corrected manifold pressure P (n).
[0035]
That is, when the estimated manifold pressure Pm (n) is close to the atmospheric pressure in this way, the throttle passage intake air amount Qth calculated based on the pressure ratio Pm (n) / P0 is hunted under the influence of the digital error of the ECU 21. As a result, the prediction accuracy of the corrected manifold pressure P (n) using the throttle passage intake air amount Qth is greatly reduced. Therefore, in such a case, a significant error in the corrected manifold pressure P (n) due to hunting is suppressed by setting the manifold pressure average value Psave as the corrected manifold pressure P (n). Thus, the fuel injection amount Qinj can be controlled more appropriately.
[0036]
On the other hand, when the difference ΔTPS between the target throttle opening TPSobj and the actual throttle opening TPS is equal to or larger than the predetermined positive value ΔTPS0 in step S38, the predicted gain Kgain is increased and corrected to 2.0 in step S40, and so on. In step S46, a larger value is calculated as the pressure change amount ΔP for two strokes. That is, the determination in step S38 is based on the assumption that the acceleration is in the initial stage. In such a situation, the actual throttle opening TPS rapidly increases as the accelerator operation amount increases. The throttle opening TPS greatly changes between the time when (step S2 in FIG. 2) and the corrected manifold pressure P (n) are predicted (step S50 in FIG. 3). This can be a factor in the prediction delay of the corrected manifold pressure P (n). However, by increasing the pressure change amount ΔP as described above, it is possible to perform a prediction process that follows the sudden increase in the throttle opening TPS. Further, it is possible to prevent a prediction delay of the corrected manifold pressure P (n), and to realize more appropriate fuel injection control.
[0037]
Further, since the throttle opening TPS at the time of deceleration gradually decreases as compared with the increase state of the actual throttle opening TPS in the early stage of acceleration, the corrected manifold pressure P (n) is sufficiently corrected even with a relatively small predicted gain Kgain. In addition, if the prediction gain Kgain larger than necessary is applied, there is a risk that the prediction accuracy may be lowered. Since normal prediction gain Kgain = 1.0 is applied at the time of deceleration, an appropriate prediction gain Kgain is always applied regardless of acceleration / deceleration, and an appropriate corrected manifold pressure P (n) prediction process is realized. be able to.
[0038]
This is the end of the description of the embodiment, but the aspect of the present invention is not limited to this embodiment. For example, in the above embodiment, the intake air amount calculation device for the engine 1 of the speed density system that controls the fuel injection based on the manifold pressure Ps is embodied, but the fuel injection is performed based on the intake air amount detected by the air flow sensor. You may apply to the engine to control. Even in this case, the intake air amount as the intake correlation amount can be accurately predicted using the throttle passage intake air amount Qth obtained from the effective opening area S.
[0039]
In the above embodiment, the corrected manifold pressure P (n) is used for fuel injection control. However, the application is not limited to this, and may be used for ignition timing control, for example. In this case, knocking during transient operation can be suppressed by appropriate ignition timing control, and good torque characteristics can be realized.
Furthermore, in the above embodiment, the throttle passage intake air amount Qth is used for the process of predicting the corrected manifold pressure P (n). However, the throttle passage intake air amount Qth obtained from the effective opening area S is not affected by the turbulence. Since the intake air amount is small, it can be used for various controls other than prediction of the corrected manifold pressure P (n), for example, as an alternative to the throttle opening TPS.
[0040]
【The invention's effect】
As described above, according to the engine intake amount calculation device of the first aspect of the present invention, the intake amount passing through the throttle is increased based on the effective opening area in consideration of the influence of the turbulent flow generated at the edge portion of the throttle. It can be calculated with accuracy.
According to the engine intake air amount calculation device of the invention of claim 2, the intake air amount passing through the throttle can be calculated with high accuracy based on the effective opening area in consideration of the influence of the turbulent flow generated at the edge of the throttle. As a result, the intake correlation amount after a predetermined number of strokes can be accurately predicted using the calculated intake amount.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram illustrating an engine intake air amount calculation device according to an embodiment.
FIG. 2 is a flowchart showing a manifold pressure estimation routine executed by an ECU.
FIG. 3 is a flowchart showing an injection amount setting routine executed by the ECU.
FIG. 4 is a time chart showing changes in measured values and estimated values during throttle opening operation.
FIG. 5 is a diagram showing the results of testing the effect of differential pressure across the throttle opening area.
[Explanation of symbols]
1 Engine 6 Throttle valve 21 ECU (opening area calculating means, effective area calculating means, passing air amount calculating means, combustion chamber air amount calculating means, intake correlation amount predicting means)
24 Throttle sensor (throttle opening detection means)
25 Atmospheric pressure sensor (front / rear pressure detection means)
26 Manifold pressure sensor (front-rear pressure detection means, intake correlation amount detection means)
TPS Throttle opening Ps Manifold pressure (intake correlation amount)
Pm (n) Estimated manifold pressure (intake correlation)
P (n) Manifold pressure after correction (intake correlation amount)
ΔP Pressure change S0 Basic opening area S Effective opening area X Pressure ratio (front-rear pressure)
Qth Throttle passage intake amount Qe In-cylinder intake estimated intake amount

Claims (2)

Throttle opening detection means for detecting or estimating the opening of the throttle disposed in the intake pipe of the engine ;
And the opening area calculation means for calculating the throttle opening area from the output of the upper Symbol throttle opening detection means,
An intake pressure estimating means for estimating an intake pressure downstream of the throttle based on an output of the throttle opening detecting means;
Atmospheric pressure detection means for detecting or estimating atmospheric pressure;
Effective opening area calculating means for correcting the throttle opening area according to the output of the intake pressure estimating means and the output of the atmospheric pressure detecting means, and calculating the throttle effective opening area;
An intake flow velocity is calculated based on the output of the intake pressure estimation means and the output of the atmospheric pressure detection means, and an intake air amount passing through the throttle is calculated based on the intake flow velocity and the calculation result of the effective opening area calculation means. An intake air amount calculating device for an engine, comprising: an intake air amount calculating means. An intake correlation amount detecting means for detecting or estimating an intake correlation amount correlated with an intake state from the throttle;
Smoothing means for smoothing the output of the intake correlation amount detection means;
An intake correlation amount prediction means for predicting an intake correlation amount after a predetermined number of strokes based on the amount of change of the intake pressure estimated by the intake pressure estimation means for a predetermined period. The engine intake air amount calculation device according to claim 1 .

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