JPH10227253A - Intake air amount detector for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To memorize only the fluctuation rate of an intake air amount to an ROM, eliminate necessity that weight factors in all driving ranges are memorized, and reduce constants stored in the ROM, by self-optimizing the weight factors at the time of normal operation on the basis of the calculated result of a cylinder intake air amount equivalent signal. SOLUTION: A signal from an airflow meter 1 is converted 12 into an intake air amount signal Qa, and a reference injection pulse width TPO is calculated 13 on the basis of this intake air amount Qa and an engine speed Ne. Also, an A/F flat correction pulse widths TPTRM are calculated 14 on the basis of the TPO. While, it is judged 15 whether the operational condition of an engine is in a normal period or a transient period on the basis of the signal of a throttle opening sensor 3, and a normal/transient operation changing over part 18 is changed over according to the judged result, thereby an intercylinder intake air amount equivalent pulse width TP is calculated 19 from filter coefficients K1 and K2 being changed over, TPTRM and an air amount at the time of the previous calculation, and various kind of corrections are executed on the basis of this TP so as to determine a fuel injection amount TI.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a device for detecting the amount of intake air of an internal combustion engine.

[0002]

2. Description of the Related Art As a conventional apparatus for detecting the amount of intake air for an internal combustion engine, there is one disclosed, for example, in Japanese Patent Application Laid-Open No. 1-240752.

In order to compensate for the pulsating fluctuation of the intake air amount detected by the air flow meter, the detected value of the air flow meter is subjected to a digital filter, weighted by a filter constant, optimized, and this constant is calculated. By switching between idling and steady operation, the reliability of the signal of the intake air amount is increased. Moreover,
In this case, the constant required for each operating condition changes delicately even during steady operation, so the constant is set in all operating regions in the steady state based on the throttle opening of the engine and the number of revolutions. In, each constant is selected, and the intake air amount is appropriately corrected.

[0004]

However, in the method of storing the constants of the digital filter for eliminating the pulsation of the intake air amount detected by the air flow meter in the map in all the operation regions, these are not used. There is also a problem that the ROM to be stored becomes large and many steps are required to determine the map constant.

Accordingly, the present invention stores only the fluctuation rate of the intake air amount in the cylinder, and self-optimizes the weight coefficient based on the stored data, thereby solving the above-mentioned problem. It is an object to provide a detection device.

[0006]

According to a first aspect of the present invention, there is provided an air flow meter which generates an output corresponding to an air amount upstream of an intake throttle valve, and calculates an air amount equivalent signal per unit rotation based on the output of the air flow meter. Means for weighting and smoothing the signal corresponding to the amount of air per unit rotation to calculate a signal corresponding to the amount of cylinder intake air, and means for determining steady operation and transient operation based on the load signal of the engine. ,
Means for switching a weighting factor during a steady operation and a transient operation as a weighting of the smoothing based on the determination result;
Means for performing a self-optimization process on the weighting factor during the steady operation based on the calculation result of the signal corresponding to the cylinder intake air amount.

According to a second aspect, in the first aspect, the weight coefficient self-optimizing processing means includes means for storing a variation rate of a signal corresponding to a cylinder intake air amount required from drivability and the like; A means for calculating a signal corresponding to the amount of air per cylinder; a means for calculating the center value of the signal corresponding to the amount of air taken into the cylinder; and a means for calculating the amplitude of the signal corresponding to the amount of air per unit rotation.

[0008]

According to the present invention, the self-optimizing process of the weighting coefficient during the steady operation is performed based on the calculation result of the signal corresponding to the cylinder intake air amount, so that the ROM stores only the variation rate of the intake air amount in the cylinder. Therefore, it is not necessary to store the weighting coefficients in all the operation regions. Therefore, the number of constants stored in the ROM can be reduced, and the number of steps for setting the constants can be reduced.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.

In FIG. 1, reference numeral 1 denotes an air flow meter for measuring an intake air amount of an engine, reference numeral 2 denotes a rotation speed sensor for detecting an engine speed, and reference numeral 3 denotes a throttle opening sensor for detecting a throttle opening.

A signal (AMF) from the air flow meter 1
Is output to the unit converter 12 as an AMF output signal US obtained by digitizing an analog signal via the air flow meter output signal capturing unit 11. In the unit converter 12, AM
The F output signal US is converted to the intake air amount signal Qa per unit rotation.
Convert to

The basic fuel pulse width calculating unit 13 calculates the intake air amount Qa and the engine speed N from the speed sensor 2.
Based on e, the basic injection pulse width TPO is calculated as in the following equation.

TPO = KCONST · Qa / Ne (1) where KCONST is a constant.

The A / F (air-fuel ratio) flat correction pulse width calculator 14 calculates the A / F flat correction pulse width TTPRM based on the calculated TPO by the following equation.

TTPRM = KTRM · TPO (2) where KTRM is a coefficient for correcting an air amount and an injector error for each engine operating condition. For example, refer to a map assigned by the engine speed Ne and the load Qh0. Ask for it. As a result, fluctuations in pulse width based on the above-described error are suppressed.

On the other hand, whether the operating condition of the engine is steady or transient is determined by the steady-state transient determining unit 15 based on a signal from the throttle opening sensor 3. In addition,
The determination of the steady state or the transient state is based on the change amount of the throttle opening per unit time or the change amount of the load (for example, ΔQh0).
If the value is equal to or more than a predetermined set value, it is determined that the state is transient, and if not, it is determined that the state is steady.

The steady-state air amount operation coefficient calculation unit 16 and the transient air amount operation coefficient calculation unit 17 calculate the TPTR corresponding to the air flow meter detected air amount in the steady state and the transient state, respectively.
Filter coefficients K1 and K2 for removing M pulsation are calculated (details will be described later). The coefficients K1 and K2 in the steady state and the transient state are output to a pulse width calculating section 19 corresponding to a digital filter via a steady state transient switching section 18 which is switched by a decision signal from the steady state transient decision section 15. Is done.

The in-cylinder intake amount-equivalent pulse width calculating section 19 calculates the A / F flat correction pulse width TPT.
Using the RM, the coefficients K1 and K2 for weighting, and the air amount TP [n-1] at the time of the previous calculation, the pulse width TP corresponding to the intake air amount in the cylinder is calculated by the following equation.

TP [n] = K1 · TPTRM + K2 · TP [n−1] (3) Then, the fuel injection pulse width calculator 20 calculates the temperature correction and the like based on the TP calculated in this manner. And the fuel injection amount TI is determined.

The operation based on the above configuration is shown in the flowchart of FIG.

In step 1, the AMF signal is A / D converted and taken in as the air amount US.
Is converted into a signal Qa corresponding to the amount of intake air. This Q
a and the basic injection pulse width T based on the engine speed Ne.
Calculate PO as TPO = KCONST.Qa / Ne (step 3).

Further, at step 4, A / A is calculated based on the TPO and a correction coefficient KTRM for correcting an air amount or an error of the injector for each engine operating condition.
The F flat correction pulse width TTPRM is calculated.

In step 5, it is determined whether the operation is a steady operation or a transient operation. If the operation is a steady operation, the process proceeds to a step 6, where the TP calculation coefficients K1 and K2 in the steady state are calculated. TP calculation coefficients K1 and K2 are calculated.

In step 8, the pulse width TP corresponding to the in-cylinder intake amount is calculated by using the coefficients K1 and K2 calculated corresponding to the steady state and the transient state.
= K1.TPRM + K2.TP [n-1].

Next, a configuration for calculating the TP calculation coefficients K1 and K2 in the steady state, which is the main point of the present invention, will be described.

The A / F flat correction pulse width, in other words, the pulsating AMF detected air amount (TPTRM) is approximately obtained by equation (4), and the air amount after passing through the filter (TP) is approximately obtained by equation (5). .

TTPRM = A + B · sin (ωt) (4) TP = A + C · sin (ωt + φ) (5) Here, as shown in FIG.
C represents the amplitude.

In general, the transfer function G (j
ω) and its gain M are given by the following equations.

G (jω) = 1 / (1 + jωT) (6)
Here, T is a time constant.

M = │G (jω) │ = │1 / (1 + jωT) │ (7)
Here, the filter gain M for converting the sine wave having the amplitude B into the sine wave having the amplitude C may be set as in the following equation.

M = C / B (8) Equation (9) is obtained by squaring both sides of equation (7), and equation (10) is obtained by solving equation (9) for T. That is, M ² = 1 / {1+ (ωT) ² } (9) T = (1 / ω) · {(1 / M ² ) −1} (10) On the other hand, in a discrete system, The first-order lag is (1
It can be expressed by a weighted average as shown in equation (1), and the relationship between the weighted average coefficient K and the time constant T is as shown in equation (12).

TP [n] = K ・ TPRM + (1−K) · TP [n−1] (11) T = −Δt / Ln (1−K) (12) where t represents a calculation interval. .

When this equation (12) is solved for K, the following equation is approximately obtained.

K = 1−Ln (−Δt / T) = 1−exp (−Δt / T) (13) On the basis of such a principle, the TP calculation coefficient K1 in the steady state is
K2 is calculated. For this reason, in FIG.
Is a calculation unit for calculating the amplitude B of the TP, 23 is a calculation unit for calculating the central value A of the TP, 24 is a calculation unit for calculating the target amplitude C, and 22 is the previous TP [nm]. The RAM 25 is a ROM for storing a rate of change of TP determined in advance from a surge request or the like, that is, ΔTP / TP.

These configurations will be described in more detail with reference to FIG. First, a center value A of the pulsation of the air amount (pulse width corresponding to the intake amount in the cylinder) TP is obtained. In this example,
The average value of the pulsation cycle is taken.

The TPs up to m samples before the present time are stored in the RAM 1 in advance, read out when the calculation of the center value A is executed, and the average value is obtained.

When the engine speed is Ne [rpm], m
Is calculated by the following equation.

M = 120 / (Ne · N) Δt · i (14) where N is the number of engine cylinders, and i is an arbitrary integer.

In this case, as shown in the flowchart of FIG. 4, addresses ADD to ADD + L are allocated to the RAM 1 so that data up to L samples before TP can be stored. The data is transferred to the address obtained by adding 1 from the currently stored address for each TP calculation, and the latest value T
Store P [n] at address ADD. Thus TP
Are stored at the addresses ADD to ADD + L in the new order (steps 11 and 12). Note that L may be a maximum required number of data and is given by the following equation (15).

L = 120 / (Nemin · N) / Δt · i (15)
Here, Nemin is the minimum engine speed.

Next, when the amplitude C of the TP is obtained, the TP fluctuation rate ΔTP / TP /
The TP is stored, read out and multiplied by the above-mentioned center value (average value) A, and this is set as C. That is, C = A · ΔTP / TP (16) Further, B, which is the amplitude of TTPRM, is obtained. This amplitude B
Is calculated as shown in the flowchart of FIG.

In step 21, the center value A obtained as described above is subtracted from the A / F flat correction pulse width TTPRM, and the value is set as X.

In step 22, it is determined whether X is positive or negative. If it is positive, the flow proceeds to step 23 to determine whether X is larger than B1 stored in the RAM2. If B1
If it is larger than X, X is stored in B1, otherwise, the value of B1 is held (steps 25 and 26). Similarly, if X is negative, the process proceeds to step 24, where it is determined whether X is smaller than B2 stored in RAM2. If X is smaller than B2, X is stored in B2; The value of B2 is held as it is (steps 27 and 28).

Next, at step 29, it is determined whether or not the value of the counter j has reached m. If the value of the counter has reached m, the average value of B1 and B2 is stored in B (step 3).
0), this becomes the amplitude B, and at the same time, B1, B2, j are cleared (step 31).

On the other hand, if the counter has not reached m, the routine goes to step 32, where the counter is incremented and the above operation is repeated until j = m.

In this manner, the amplitude B is updated every m samples, and is reflected in the TP calculation in the next cycle (see FIG. 6).

Next, returning to FIG. 2, the gain M is calculated from these C and B by the aforementioned equation (8). Further, the angular velocity ω is calculated based on the engine speed Ne as in the following equation.

Ω = 2π / 120 / (Ne · N) (17) Further, the time constant T is calculated from the gain M and the angular velocity ω in accordance with the above-mentioned equation (10). The weighted average coefficient K is calculated by the equation (13) based on the time constant T thus obtained. Then, K is stored in K1 and 1-K is stored in K2, and TP is calculated based on the above-described equation (11).

As described above, in the present invention, the weighting coefficients (calculation coefficients) K1 and K2 during the steady operation are self-optimized based on the calculation result of the cylinder intake air amount equivalent signal TP. It is only necessary to memorize the rate of change of the TP to be performed.
It is possible to suppress the fluctuation and at the same time reduce the filter constant stored in the ROM.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a process of calculating a pulse width calculation coefficient corresponding to an in-cylinder intake amount.

FIG. 3 is a flowchart illustrating a control operation for calculating a pulse width corresponding to an in-cylinder intake amount.

FIG. 4 is a flowchart showing a part of the control operation.

FIG. 5 is a flowchart showing a part of the control operation.

FIG. 6 is an explanatory diagram showing a pulsating state of the intake air amount.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Air flow meter 2 Engine speed sensor 3 Throttle opening sensor 12 Unit conversion part 15 Steady transient judgment part 16 Constant air amount calculation coefficient calculation part 17 Transient air amount calculation coefficient calculation part 19 In-cylinder intake air equivalent pulse width calculation part

Claims (2)

[Claims] 1. An air flow meter for generating an output corresponding to an air amount upstream of an intake throttle valve, means for calculating a signal corresponding to an air amount per unit rotation based on the output of the air flow meter, and an air amount per unit rotation Means for calculating a signal corresponding to the cylinder intake air amount by weighting the corresponding signal and smoothing the signal; means for determining a steady operation and a transient operation based on an engine load signal; and performing the smoothing based on the determination result. Means for switching the weighting factor during steady-state operation and transient operation as a weighting of, and means for self-optimizing the weighting factor during steady-state operation based on the calculation result of the cylinder intake air amount equivalent signal. An air amount detection device for an internal combustion engine. 2. The means for self-optimizing the weighting coefficient includes means for storing a variation rate of a signal corresponding to a cylinder intake air amount required from drivability and the like, and means for calculating a signal corresponding to an air amount per unit rotation. 2. The air amount detecting device for an internal combustion engine according to claim 1, further comprising: means for calculating a center value of the signal corresponding to the cylinder intake air amount; and means for calculating the amplitude of the signal corresponding to the air amount per unit rotation.