JPH01294943A - Air amount detecting device for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve detecting precision of an air amount, by a method wherein a fundamental limit value is corrected according to an air density factor based on a ratio (difference) between an intake air amount during full running of an engine and an air amount fundamental limit value to determine a maximum limit value, and by means of the maximum limit value, an output from an air amount detecting means is limited. CONSTITUTION:Based on the number of revolutions of an engine detected by a number of revolutions detecting means (a), the fundamental limit value of an intake air amount is computed by a computing means (d). When the full running state of an engine is detected by a full running detecting means (c), an air density computing means (e) computes an air density factor, by means of which a fundamental limit value is corrected, based on a ratio or a difference between an intake air amount detected by the intake air amount detecting means (a) and a fundamental limit value. A maximum limit value computing means (f) computes an intake air amount maximum limit value through correction of the fundamental limit value according to air density, and a maximum value limit means (g) performs limitation so that an output from the intake air amount detecting means (a) does not exceeds an intake air amount maximum limit value.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a device for accurately detecting the amount of intake air required as input information for combustion control of an internal combustion engine such as an automobile.

(Prior Art) Generally, the amount of fuel required by an engine in a certain operating state uses the intake air amount of the engine at that time as one important parameter.

Conventional air flow rate detection devices for internal combustion engines that determine the amount of fuel required by the engine from the amount of intake air include, for example, "Car Electronics Comprehensive Technical Data" (edited by Japan Industrial Technology Center, published October 1981). ) are listed.

In this device, the air flow rate is extracted from the rotational displacement of a measuring plate of an air flow meter installed in the intake pipe, and converted into an electrical signal using a potentiometer.

This electrical signal is input to the control unit 6 and is divided by a predetermined trigger corresponding to the engine speed. The divided electrical signals correspond to the intake air amount for each cylinder, and based on this, the fuel supply amount is determined based on steady state conditions so as to achieve the target air-fuel ratio.

However, with regard to the intake air flow rate detected by the engine, for example during sudden acceleration, the collector volume (manifold pressure filling bone) between the flow valve and the intake valve
This may cause a so-called overshoot phenomenon in which the amount of intake air detected by the air flow meter temporarily becomes extremely larger than the amount of intake air actually required by the engine. In such a case, the basic injection amount 'rp calculated based on the intake air amount is shown in Figure 1O (
As shown by the solid line in B), the air-fuel ratio temporarily increases significantly, causing engine misfires and ignition disturbances, resulting in deterioration of drivability and exhaust emission/notion characteristics.

In order to solve this problem, for example,
A device described in Japanese Patent No. 8-173429 has been proposed. In this device, a limit value Tρmax as shown in the same figure (B) is set for the basic injection amount Tp according to the engine speed N,
This T pmax is used to cut the overshoot of the air amount in the portion shown in FIG.

(Problem to be Solved by the Invention) However, in such a conventional air amount detection device for an internal combustion engine, a uniform limit value T p is set for N.
Since the configuration was such that the maximum value of 'rp is limited by (The air-fuel ratio is set to the rich side with some margin in order to reduce the
emissions, etc.). Further, the above-mentioned overshoot amount is shown as an error with respect to the air amount in the injection valve (see the broken line in FIG. 3B), and this error is greatly affected by the difference in air density. In other words, as shown in the same figure (C,), the amount of air in the injector is also small at high altitudes where the air density is low, but the current Tpmax does not take into account such differences in air density and is set at a constant value. As a result, especially at high altitudes, the error between the injector air amount and T pmax widens, leaving a large overshoot, resulting in a significant change in the air-fuel ratio and a significant deterioration of exhaust emission characteristics. Put it away. Furthermore, if T pmax is too small, especially when the true flow rate is large such as when the intake temperature is low (high air density), T p will decrease as shown by the broken line in FIG.
Since the amount of air in the injector is limited to a small value by max, there is a problem in that the lean air-fuel ratio deteriorates the combustion state, resulting in poor drivability or, in the worst case, misfire.

(Object of the Invention) Therefore, the present invention calculates an air density coefficient based on the ratio or difference between the intake air amount when the engine is fully open and the basic limit value of the air amount, and calculates the air density coefficient according to the air density coefficient. By correcting the basic limit value to find the maximum limit value and preventing the output of the air amount detection means from exceeding the maximum limit value, overshoot is prevented regardless of changes in intake temperature, cooling water temperature, and atmospheric pressure. The purpose is to properly cant the intake air amount and improve the detection accuracy of the intake air amount.

(Means for Solving the Problems) In order to achieve the above object, the air amount detection device for an internal combustion engine according to the present invention detects the intake air amount by detecting the intake air amount of the engine, as shown in FIG. means a, a rotation speed detection means for detecting the rotation speed of the engine, fully open detection means C for detecting a fully open state of the engine, and a basic limit value for calculating a basic limit value for the amount of intake air based on the engine rotation speed. a calculation means d; and an air density calculation means e for calculating an air density coefficient for correcting the basic limit value based on the ratio or difference between the output of the intake air amount detection means a and the basic limit value when the engine is in a fully open state. , the basic limit value is calculated by air density calculation means e
a maximum limit value calculating means f which corrects the air quantity maximum limit value according to the output of the air quantity detecting means f, and a maximum limit value 1 which limits the output of the air quantity detecting means a so that it does not exceed the air quantity maximum limit value.
It is equipped with a limiting means g.

(Function) In the present invention, an air density coefficient is calculated based on the ratio or difference between the intake air amount when the engine is fully open and the basic limit value of the air amount, and the basic limit value is calculated according to the air density coefficient. is corrected and the maximum limit value is calculated. Then, the output force of the air amount detection means is limited to 9 y so that it does not exceed the maximum limit value. Therefore, regardless of changes in the intake air temperature, cooling water temperature, and atmospheric pressure, overshoot can be properly canted, and the detection accuracy of the intake air amount is improved.

(Example) Hereinafter, the present invention will be explained based on the drawings.

2 to 9 are diagrams showing an embodiment of an air amount detection device for an internal combustion engine according to the present invention, and this embodiment is an example in which the present invention is applied to a fuel supply control device. First, the configuration will be explained.

FIG. 2 is a diagram showing the overall configuration of this device. In FIG. 2, l is an engine, intake air passes through an intake pipe 3 from an air cleaner 2, and fuel is injected from an injector 4 based on an injection signal St. Then, the exhaust gas combusted in the cylinder is introduced into the catalytic converter 6 through the exhaust pipe 5, and the harmful components (Co, HC,
, NOx) is purified by a three-way catalyst and discharged.

The intake air flow rate Qa is detected by a hot wire type air flow meter (intake air amount detection means) 7 and controlled by a throttle valve 8 in the intake pipe 3. In addition, air flow meter 7
The type may be a hot film type, as long as it measures the flow rate of intake air. Therefore, a flap type may be used, but the negative pressure sensor is excluded.

The opening TVO of the throttle valve 8 is determined by the throttle valve opening sensor (opening detection means).
9, and the rotation speed N of the engine l is detected by a crank angle sensor (rotation speed detection means) lO. Further, the temperature Tw of the cooling water flowing through the water jacket is detected by a water temperature sensor 11, and the oxygen concentration in the exhaust gas is detected by an oxygen sensor 12. The oxygen sensor 12 used has a characteristic that its output (S) changes suddenly at the stoichiometric air-fuel ratio. Furthermore, the idle state of the engine l is detected by the idle switch 13.

The air flow meter 7, throttle valve opening sensor 9, crank angle sensor 10, and water temperature sensor 11 constitute an operating state detecting means 14, and the outputs from the operating state detecting means 14, oxygen sensor 12, and idle switch 13 are controlled. input to unit 20.

The control unit 20 has functions as a full-open detection means, a basic limit value calculation means, an air density calculation means, a maximum limit value calculation means, and a maximum value restriction means, and includes a CPU 21,
It is composed of a ROM 22, a RAM 23, and a 10-board 24. The CPU 21 imports necessary external data via the I10 boat 24 according to the program stored in the ROM 22, and while exchanging data with the RAM 23, processes values necessary for air amount detection and combustion control. and outputs the processed data to the I10 port 24 as necessary. I10 boat 24
The signals from the sensor group 7.14.12 are input to the I10 boat 24, and the injection signal Si is output from the I10 boat 24. The ROM 22 stores calculation programs for the CPU 21, and the RAM 23 stores data used in calculations in the form of a map or the like.

Next, the effect will be explained.

FIG. 3 is a flowchart showing a program for calculating the AvTp maximum limit value Tpr*ax, and this program is executed once every 10 ms, for example. First, P.
If it is ON, the air density coefficient A dens t is looked up from the table map shown in FIG. 4 based on the cooling water temperature Tw at P2, and the process is completed.

When the start switch is OFF, AvT is determined from the table map shown in Fig. 5 based on the engine speed N at P3.
Look up the p limit value table value (basic limit value) Ttpmax, and determine in P4 whether the throttle valve opening TVO is greater than or equal to the fully open judgment throttle valve opening WOTTVO# (TVO≧WOTTVO#), and determine whether TVO≧WOTTVO#. When #, it is determined by P whether the engine rotation speed N is a predetermined value (for example, 11000 rpm) or higher. When N≧11000rp, P, then N
Is the learning condition rotation speed upper limit GTPMN# or higher (N≧GTP
If N<GTPMN#, it is determined that the rewriting condition is satisfied, and at P, the current flash A/F correction pulse width TrTp is set to the AvTp limit value table value. It is compared with the value (Ttpmax XAdenst) obtained by multiplying Ttpmax by the previous Adenst. Here, the above T tpn+ax and TrTp will be explained using a program shown in FIG. 7, which will be described later. Tr'
When rp≧T tpmax X A dens t, in P6 rewrite A dens t according to the following formula
When rTp<Ttpmax XAdenst, P is used to rewrite Adenst according to the following equation (2). Here, A
dens t is W OT (Wide open t
hrotle: It is the ratio between time'rp (at full speed) and Ttpmax.

A dens - old Adenst + D A D
ENA#--■However, DADENA#: Learning coefficient rewriting amount plus A dens - old Adenst + D A D
ENS#--■However, DADENS#: learning coefficient rewriting amount minus then A dens t in steps PIO~PI:l
is limited to the air density upper limit value ADEMX# and the air density lower limit value ADEMN# (ADEMX#≦Adens
t≦ADEN#). That is, Adens in PIG
Determine whether t is greater than or equal to ADEMX#, and
<For ADEMX#, set A dens t by pH.
Limit to EMX# (Adenst = A D E M
X #).

When A dens t≧ADEMX#, A in PI2
Determine whether or not dens t is smaller than ADEMN#, and if Adenst≧ADEMN#, PI3 selects A d
Restrict enst to ADEMN# Adenst =
A D E M N #), Adenst < A D E M
If N#, it is determined that the value is within the limit value and the process proceeds to PI3.

On the other hand, when TVO<WOTTVO# at P4, N at P
When < 1100 Orp or at P6, N < GTP
In the case of MN#, it is determined that the conditions for calculating A dens L are not satisfied, and the process directly proceeds to PI3. P
In I3, AVTp maximum limit value Ttρma according to the following formula
Calculate x and end the current process.

Tpmax= Ttpmax
enst+YUTORI #・・・・・・
(2) However, Kqho: Correction amount look-amplified from the table map shown by the solid line in FIG. 6 based on α-N flow 1Qho. Incidentally, the α-N flow rate Qho is used to determine the air flow rate from the throttle valve distance TVO and the rotational speed N, and is already known.

■ In 2, YUTORI# is a margin, and a predetermined margin is given to the maximum limit value, but if Kqho is set as a characteristic that takes the margin into account in advance, as shown by the broken line in Figure 6, this YUTORI #ha is no longer needed.

Figure 7 shows the pulse width equivalent to the flow rate of the injection valve (smooth injection!f)
This is a flowchart showing a program for calculating A V T I), and this program is executed once every 10 ms, for example. First, the output of the air flow meter 7 is read using PK+ to obtain the intake air, lQa. this is,
For example, with a table look amplifier.

Next, in pzz, the smoothing part basic pulse width T is calculated according to the following formula (■)
Calculate po.

Next, PI3 calculates the basic pulse width T by weighting the average of Tpo.
Calculate p. As a result, pulsations based on the output of the air flow meter 7 are smoothed out. In P24, the flat A/F corrected basic pulse width T r T p is determined according to the following equation.

TrTp=TpxKflat . + .

Next, pzs compares TrTp with the maximum limit value T pmax calculated using the program in FIG. 3, and TrTp>Tp
When n+ax, limit TrTp to T pmax at pi6 and proceed to PX3, and when T r T p≦T pmax, jump PX6 and proceed to pi. In PX3, delay correction pulse width T as α-N preemption correction pulse width
Find hs tp. This is the value Th5 looked up from the table with interpolation calculation based on α-N flow 1Qho.
It is determined as the amount of change in tp every 1 Qrr, s. However, if the amount of change is below the correction determination level, Th5tp=0
If the amount of change is negative (deceleration), the amount of change is multiplied by a predetermined deceleration correction rate. T hs tp is a term that anticipates changes in the throttle valve 8 and corrects the injection amount with good responsiveness.

Then, in pzs, smooth injection 1AVTp according to the following formula
(corresponding to smooth intake air volume).

AvTp=TrTpXFload+AvTp-.

X (1-Fload) +Th5tp...
・■However, AvTp-,: Previous AvTp ■In the formula, F 1oad is a weighted average coefficient,
1oad=Tfload+K2D (deceleration only). Since Tfload is a function of only the intake volume, it is determined by a map from the flow area AA determined by the throttle valve 8 and (rotation speed x exhaust gas i) NMV. Therefore, the first and second terms of Equation 0 are the weighted average value using F 1oad of the flat A/F correction basic pulse width TrTp calculated based on the pulsation correction value of the output of the airflow make 7, In other words, the temporary delay of TrTp is calculated (by software)
This corresponds to the part to be calculated. In addition, the third term in Equation 0 is a preemption correction part based on the throttle valve opening TVO, and this part is
This example is disclosed for the first time.

The effect of adding the third term Th5tp is shown in FIG. 9. In Fig. 8, when acceleration occurs at a certain timing, the basic pulse width Tpo, Tp changes slightly after the change in the throttle valve opening, and the waveform corrected by 790% Tp is shown as a flat corrected basic pulse width TrTp in the same figure. (
C). On the other hand, the α-N flow rate Qho changes in a stepwise manner as shown in FIG. 3(D) depending on the degree of opening of the throttle valve 8, and the delay correction pulse width Th5tp is calculated based on the amount of change in the degree of opening. On the other hand, smooth injection amount AVT
p is given by the first-order lag of TrTp, and in the case of conventional phase control without Th5tp, the change is shown by the dashed-dotted line in the figure, resulting in lack of responsiveness. At this time, the suction negative pressure is shown by a broken line and is approximately equal to the air flow rate of the injection valve section (injector 4 section), but this cannot follow the change in the opening degree of the throttle valve 8 without delay. In addition, the amount of fuel adhering to the wall surface of the intake pipe 3 is also determined by the intake volume.

On the other hand, in the AVTp of this embodiment, as shown by the solid line in the figure, the correction term T hs tp is added as α-N prefetch correction (10 m s prefetch correction), so the responsiveness is extremely high. It is a good match to the actual change in air flow rate. An example of a highland area is also shown.

In this way, Tp at WOT and Tp stored in advance
Tpmax is obtained by learning correction of T Lpmax based on the ratio of pmax to the reference value T tpmax (corresponding to the air density coefficient A dens t), and 'rp is this T ptaa
It is limited to not exceed x. Therefore, as shown by the solid line in FIG. 9(A), even when AvTp is large at low intake temperature, the limit level of T pmax is appropriate in accordance with AvTp, and overshoot is appropriately cut. In addition, even in highlands, the optimal limit level T pmax is set according to AvTp as shown in the broken line in Figure 9 (A) or Figure 8 (F), so overshoot can be appropriately cut. I can do it. In this embodiment, by performing phase control (that is, calculation of TrTP) using a signal limited by Tpmax, it is possible to improve the calculation accuracy of AvTp as the amount of air in the injector, as shown in FIG. As shown in B), the flatness of the air-fuel ratio can be sufficiently improved. As a result, drivability and exhaust gas purification performance can be significantly improved.

Note that the maximum air amount limit value in the claims is the intake air i.
Needless to say, this is just a precaution to the basic expression of Qa as the injection pulse width, and even in this embodiment, Tpmax for limiting TP is used as the maximum air amount limit value in the claims. There is.

(Effect) According to the present invention, an air density coefficient is calculated based on the ratio or difference between the intake air amount when the engine is fully open and the basic limit value of the air amount, and the air density coefficient is calculated based on the air density coefficient. The limit value is corrected to find the maximum limit value, and the output of the air amount detection means is prevented from exceeding the maximum limit value, so overshoot is prevented regardless of changes in intake air temperature, cooling water temperature, or atmospheric pressure. It can be cut appropriately and the accuracy of detecting the amount of air can be increased.

[Brief explanation of the drawing]

FIG. 1 is a basic conceptual diagram of the present invention, FIGS. 2 to 9 are diagrams showing an embodiment of an air amount detection device for an internal combustion engine according to the present invention, FIG. 2 is an overall configuration diagram thereof, and FIG. is a flowchart showing a program for calculating the AvTp maximum limit value Tpmax, FIG. 4 is a table map of the person dens t, FIG. 5 is a table map of the person T tpmax, FIG. 6 is a table map of the person K qho, FIG. 7 is a flowchart showing a program for calculating the pulse width AvTp corresponding to the injection valve flow rate, FIG. 8 is a timing chart for explaining its action, FIG. 9 is a timing chart for explaining its effect, and FIG. FIG. 10 is a timing chart for explaining the problems of the conventional air amount detection device for an internal combustion engine. ■・・・Engine, 7・・・Air flow meter (intake amount detection means),
10...Crank angle sensor (rotation speed detection means)
, 20...Control unit (fully open detection means, basic limit value calculation means, air density calculation means, maximum limit value calculation means, maximum value restriction means).

Claims (1)

[Scope of Claims] a) intake air amount detection means for detecting the intake air amount of the engine; b) rotation speed detection means for detecting the engine rotation speed; c) fully open detection means for detecting the fully open state of the engine. d) a basic limit value calculation means for calculating a basic limit value of the intake air amount based on the engine speed; and e) a ratio between the output of the intake air amount detection means and the basic limit value when the engine is in a fully open state, or an air density calculation means for calculating an air density coefficient that corrects the basic limit value based on the difference; An air amount detection device for an internal combustion engine, comprising: limit value calculation means; and g) maximum value limiting means for limiting the output of the air amount detection means so that it does not exceed the air amount maximum limit value.