JPH0814262B2 - Control device for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an internal combustion engine, and more particularly to a device for improving transient operation performance by increasing fuel supply amount control accuracy during transient operation.

<Prior Art> The following is known as a control device for an internal combustion engine (see Japanese Utility Model Application No. 60-06655, etc.).

That is, the intake air flow rate and the intake pressure are detected as the state quantities related to the intake air, and the basic fuel supply amount T _P is calculated based on these and the detected value of the engine speed. Then, the basic fuel supply amount T _P is set to various correction factors COEF set based on operating conditions such as engine cooling water temperature, air-fuel ratio set based on the air-fuel ratio obtained through detection of oxygen concentration in exhaust gas. The final fuel injection amount T _i is calculated by correcting the feedback correction coefficient LAMBDA, the correction amount T _S by the battery voltage, etc. (T _i = T _P · COEF · LAMBDA + T _S ), and the calculated amount of fuel is the fuel. It is supplied to the engine by an injection valve or the like.

Further, during the transient operation, the air-fuel ratio feedback correction coefficient LAMBDA is clamped to a reference value, and the acceleration increase correction coefficient or the deceleration decrease correction coefficient is calculated by the change rate ΔTVO of the throttle valve opening, and the steady-state By multiplying the basic fuel injection amount T _P by these correction factors, the fuel is increased during acceleration or decreased during deceleration to improve transient operation performance.

<Problems to be Solved by the Invention> By the way, in the device for calculating and setting the fuel supply amount and electronically controlling it in this way, during the transient operation, the change rate ΔTVO of the throttle valve opening is used to increase or decrease the correction coefficient. Since the setting is made, for example, when the throttle valve opening changes from 0 to 10 ° per unit time and when it changes from 70 ° to 80 °, the amount of air taken into the cylinder changes. The former is larger than the latter. This is the throttle valve opening TV
This is because the intake air flow rate Q is not linear with respect to O and varies depending on the engine speed N. Therefore, if the increase correction coefficient is matched according to the former (0 to 10 °), in the latter (70 ° to 80 °), the increase correction coefficient is too large and the air-fuel ratio becomes overrich.
The resulting increase in the amount of exhaust gas, smoldering of the spark plug, afterburn, and the occurrence of hesitation.

There is also an idle control valve installed in the passage that bypasses the throttle valve to control the idling speed by controlling the bypass air flow rate. Since there is no consideration in the above, it is not possible to suppress the fluctuation of the air-fuel ratio due to the change of the bypass air flow rate, and there is a disadvantage that a large rotation fluctuation occurs when switching between the N range and the D range in a vehicle equipped with a torque converter. In view of the above, the applicant of the present application first obtains the opening area of the intake system that is variably controlled based on the throttle valve opening and the like, and improves the transient motion performance by correcting the increase / decrease of fuel based on the rate of change. We propose what you have planned.

In this case, the intake air flow rate and the opening area of the intake system variable control section are areas where the opening area is small and the intake flow velocity on the downstream side of the variable control section becomes the sonic velocity (hereinafter referred to as sonic flow area), as shown in FIG. However, the linearity is not maintained in a region where the opening area is large, and it also changes depending on the engine speed N. Therefore, the fuel increase / decrease correction amount during transient operation is set only by the change rate of the opening area. Then, it was hard to say that the transient operation performance from the high load state was always satisfied well.

For example, even when the throttle valve opening also changes from 30 ° to 40 °, it is the same as when the engine speed is 800 rpm.
At 00 rpm, since the change rate of the intake air flow rate is smaller in the former case where the intake pressure is higher, if the air-fuel ratio is matched at 3600 rpm, the air-fuel ratio at 800 rpm becomes rich, causing afterburn and backfire. The increase in CO and HC is unavoidable, and conversely 3600 rp if matched with the air-fuel ratio at 800 rpm
The air-fuel ratio at m becomes lean, causing a sudden torque decrease shock due to the occurrence of rising misfire, hesitation, and NO.
_It sometimes caused an increase in _X.

The present invention has been made in view of such a conventional problem, and in addition to the rate of change of the opening area that is variably controlled by the throttle valve or the idle control valve of the intake system, the upstream side and the downstream side of the variable control unit The internal combustion engine ensures good transient operating performance over the entire operating range by setting the amount of fuel increase / decrease correction during transient motion using the correction coefficient of the intake air flow rate that is a function of the pressure ratio with the side An object of the present invention is to provide a fuel supply control device of the above.

<Means for Solving Problems> Therefore, according to the present invention, as shown in FIG. 1, the operating state detecting means for detecting at least the state quantity relating to the intake air and the basic fuel supply based on the detected operating state. A basic fuel supply amount setting means for setting the amount, an opening area calculation means for calculating the opening area of the intake system that is variably controlled, an opening area change rate calculation means for calculating the change rate of the calculated opening area, Correction coefficient ψ of the intake air flow rate according to the ratio of the pressure P _A on the upstream side of the variable control unit of the intake system and the pressure P _B on the downstream side. (K: specific heat ratio of air) Intake air flow rate correction coefficient calculation means, based on the calculated opening area change rate and correction coefficient ψ of intake air flow rate, fuel increase during transient operation A fuel correction amount setting means for setting a reduction correction amount, and a fuel supply means for supplying to the engine the amount of fuel obtained by correcting the set basic fuel supply amount by the increase / decrease correction amount.

<Operation> The basic fuel supply amount is set by the basic fuel supply amount setting means based on the intake air pressure, the intake air flow rate, and other state quantities related to intake air and the engine speed that are detected by the operating condition test means. Is set.

On the other hand, the opening area calculating means calculates the opening area of the intake system which is variably controlled by the throttle valve, the idle control valve, etc., and the opening area change rate calculating means calculates the change rate of the opening area.

In addition, the intake air flow rate correction coefficient calculation means calculates an intake air flow rate correction coefficient according to the pressure ratio between the upstream side and the downstream side of the variable control unit.

Then, the fuel correction amount setting means sets the fuel increase / decrease correction amount during the transient operation based on the opening area change rate and the intake air flow rate correction coefficient, and the basic fuel supply amount is adjusted by the increase / decrease correction amount. Fuel is supplied to the engine by the fuel supply means.

Here, the process of deriving the flow rate correction coefficient ψ and the reason for using it will be described.

Since the flow of the intake air in the variable control unit of the opening area such as the throttle valve and the idle control valve can be regarded as an isentropic flow, the flow rate Q in that case is expressed by the following equation as well known. .

A is the opening area in the variable control unit, P _A is substantially constant at atmospheric pressure, and ρ _a is substantially constant at air density.

Here, by defining the flow rate correction coefficient ψ as described above, the intake air intake flow rate Q is expressed as follows.

The change amount ΔQ of the intake air flow rate Q when the opening area A is changed by ΔA can be calculated as ΔQ≈k · ψ · ΔA k as a constant. Here, when the opening area of the variable control unit becomes equal to or less than a certain value such as during idling and the intake pressure P _B on the downstream side reaches a critical negative pressure, ψ is maintained at a certain maximum value, and a so-called sonic flow results in ΔQ. Changes substantially in proportion to ΔA, but when the opening area is larger than that, the correction coefficient ψ is a function that changes depending on the upstream / downstream pressure ratio, as shown in FIG. When the change in the downstream pressure due to the change in the opening area is small, the above equation holds.

Therefore, based on the rate of change of the opening area and the correction coefficient ψ, the fuel correction amount for ΔQ that changes from that time is calculated with respect to the basic fuel supply amount obtained for the opening area detected during the calculation of the fuel supply amount. Can be set.

With this configuration, the intake air flow rate correction coefficient is used for correction even during a transient operation from a high load region where the opening area of the intake system is large and linearity is not maintained between the opening area and the intake air flow rate. It is possible to secure excellent driving performance.

<Example> An example of the present invention will be described below with reference to the drawings.

2, an internal combustion engine 1 includes an air cleaner 2, an intake duct 3, and a throttle chamber 4.
Air is sucked in through the intake manifold 5. The air cleaner 2 is provided with an intake air temperature sensor 6 that detects an intake air (atmosphere) temperature. In the throttle chamber 4,
A throttle valve 7 which is linked with an accelerator pedal (not shown) is provided to control the intake air flow rate Q. The throttle valve 7 has
A throttle sensor 8 including an idle switch 8A that detects the opening TVO and is turned on at the idle position is additionally provided. Intake manifold 5 downstream of the throttle valve 7
Is provided with an intake pressure sensor 9 for detecting the intake pressure, and an electromagnetic fuel injection valve 10 is provided as fuel supply means for each cylinder. The fuel injection valve 10 includes a control unit 11 including a microcomputer described later.
The valve is driven to open by an injection pulse signal from a fuel pump (not shown), and fuel supplied under pressure from a fuel pump (not shown) and controlled to a predetermined pressure by a pressure regulator is injected into the intake manifold 5. In addition, the cooling temperature in the engine cooling jacket
A water temperature sensor 12 that detects T _W is provided, and an oxygen sensor 14 that detects the air-fuel ratio in the intake air-fuel mixture by detecting the oxygen concentration in the exhaust gas in the exhaust passage 13 is provided.

The control unit 11 counts the crank unit angle signal output in synchronization with the engine rotation from the crank angle sensor 15 for detecting the engine rotation speed for a certain period of time or measures the cycle of the crank reference angle signal to measure the engine rotation speed. Detect N.

In addition, the transmission is provided with a vehicle speed sensor 16 for detecting the vehicle speed and a neutral sensor 17 for detecting the neutral position, and these signals are transmitted to the control unit 11
Is input to

Further, an idle control valve 19 that controls the idle speed is provided in the auxiliary air passage 18 that bypasses the throttle valve 7.

In addition to the intake pressure sensor 9, the various sensors described above constitute an operating state detecting means.

The control unit 11 calculates the fuel injection amount T _i based on the various detection signals detected as described above, and drives and controls the fuel injection 10 based on the set fuel injection amount T _i. The idle speed is controlled by controlling the opening degree of the idle control valve 19.

Next, the operation will be described with reference to the flowcharts of FIG.

FIG. 3 is an intake pressure detection routine executed every set period (for example, 4 ms). In step 1, the output voltage from the intake pressure sensor 9 is input and the one-dimensional stored in the ROM according to the output voltage. Obtain the intake pressure P _B [mmHg] from the map by searching.

FIG. 4 shows a fuel injection amount calculation routine executed every set period (for example, 10 ms), and in step 11, the intake pressure obtained as described above and detection signals from various sensors are input. .

In step 12, the change amount ΔTVO of the throttle valve opening TVO per unit time (for example, 10 ms which is the execution cycle of this routine).
To calculate.

In step 13, it is determined whether or not the acceleration / deceleration operation (steady operation) is performed depending on whether or not the magnitude of the change amount | ΔTVO | is equal to or more than a set value. If the determination is YES, the process proceeds to step 14 and this YES It is determined whether the determination is the first time.

When the acceleration / deceleration operation is started, which is the first determination in step 14, the acceleration / deceleration timer TACC is reset to 0 in step 15, and then the process proceeds to step 16 and the flag FALT is reset to 0 to stop the altitude estimation learning. Then proceed to step 20.

When it is determined in step 13 that the operation is steady and when it is determined in step 14 that the acceleration / deceleration is detected for the second time or later, the process proceeds to step 17, the timer TACC is counted up, and then the process proceeds to step 18, where the value of the timer TACC is set. But the cooling water temperature T _W
It is determined whether it is longer than the fuel delay time TDEL (the response delay time until the injected fuel reaches the combustion chamber, which is large due to the deterioration of fuel vaporization at low water temperature) set according to If NO, the process proceeds to step 16, but if YES, the process proceeds to step 19 to set the flag FALT to 1 and then proceeds to step 20. That is, the flag FALT is set to 0 to stop the altitude estimation learning during the transient operation and the intake air flow rate immediately after the transient operation, and the altitude estimation learning is performed under other conditions where the intake air flow rate is stable. Set the flag FALT to 1 to execute.

Next, at step 20, based on the intake pressure P _B detected by the intake pressure sensor 9, the basic volume efficiency η _V0 is retrieved and set from the one-dimensional map stored in the ROM. The higher the intake pressure P _{B, the} higher the basic volume efficiency η _V0 is set.

In step 21, the latest minute correction coefficient K _FLAT set by the minute correction coefficient setting routine described later and the latest altitude correction coefficient K _ALT set by the altitude correction coefficient setting routine also described later are input.

In step 22, the volume efficiency Q _CYL of fresh air is obtained by multiplying the basic volume efficiency η _V0 , the minute correction coefficient K _FLAT and the altitude correction coefficient K _ALT set as described above.

In step 23, the temperature correction coefficient K _TA is retrieved and set from the one-dimensional map stored in the ROM based on the intake air temperature T _A detected by the intake air temperature sensor 6. The lower the intake air temperature T _{A, the} larger the intake charge amount (mass) even with the same intake pressure, and the temperature correction coefficient K _TA is set to increase accordingly.

In step 24, the basic injection amount T _P of fuel is calculated by the following equation.

T _P = K _CON , P _B , Q _CYL , K _TA K _CON is a constant.

The step 24 corresponds to the basic fuel supply amount setting means.

In step 25, calculated by the retrieval or the like from the aperture area from the throttle valve opening TVO A _TH, a map from the opening duty ratio ISC _DUTY idle control valve 19 the opening area A _ISC of the bypass passage 18 is stored in each ROM, In addition, the total opening area A is calculated by adding the opening area A _LEAK corresponding to the leakage of air from the throttle adjust screw, the air regulator, etc. (not shown). That is, the step 25 corresponds to the opening area calculation means.

In step 26, the amount of change in the opening area A calculated as described above per unit time (execution cycle (10 ms) of this routine, etc.), that is, the opening area change rate ΔA is calculated. The step 26 corresponds to the opening area change rate calculation means.

In step 27, the intake air flow rate correction coefficient ψ is obtained by searching the map stored in the ROM. Here, the intake air flow rate correction coefficient ψ is obtained as a function determined by the intake pressure upstream of the throttle valve, that is, the atmospheric pressure P _A and the intake pressure P _B ratio detected by the intake pressure sensor 9 on the downstream side of the throttle valve.
With the atmospheric pressure kept constant (= 760 mmHg), the map can be assigned as a function of the intake pressure P _B as shown in FIG.

As shown in the figure, this value indicates that the intake pressure P _B has reached the specified value (360 mmH
g) The following sonic flow region, in the region but is kept constant the intake pressure P _B exceeds a predetermined value has a characteristic that decreases as the intake pressure P _B increases. The step 27 corresponds to the intake air flow rate correction coefficient setting means.

In step 28, a delay time # 1TIME from the present time, that is, the time point when ΔA is calculated until the intake valve is opened next to each cylinder
# 4 Calculate TIME. Specifically, it can be obtained as a value proportional to Δθ / N based on the angle difference Δθ between the current crank angle position and the crank angle position corresponding to the intake valve opening timing of each cylinder and the current engine speed N. .

In step 29, the correction amount ΔT _Pi (i = 1 to 4) of the basic injection amount T _P when the intake valve of each cylinder is opened is calculated by the following equation.

ΔT _Pi = ΔA / N × ψ × # iTIME × K where K is a constant and the intake air flow rate is Q
It is set as a value proportional to T _P · N / Q.

That is, ΔA is the amount of change in the opening area A per unit time as described above, and therefore ΔA × # iTIME represents the amount of change in the opening area of the cylinder i from the ΔA calculation to the intake valve opening. Then, the intake air flow rate correction coefficient ψ
By multiplying by, Q / N and A / N × over the entire speed range
Since the relationship between [psi is maintained in a linear, Delta] Q When Delta] Q of the amount of change in the intake air flow rate Q from the time of .DELTA.A operation until the opening the intake valve = ΔA / N × ψ × # iTIME next, thus this T _P
・ ΔT _Pi can be obtained by multiplying the constant K proportional to N / Q.

In the present embodiment, since the correction amount ΔT _Pi is set in consideration of the delay time #iTIME as described above, more accurate correction control can be performed, but even if the delay time #iTIME is not considered, high accuracy is achieved. Correction control can be performed.

In step 30, the correction amount ΔT _Pi calculated as described above
Is added to the basic fuel injection amount T _P obtained in step 24 to correct and set the basic fuel injection amount T _{Pi of} each cylinder.

Next, at step 31, the cylinder discrimination is performed based on the reference signal from the crank angle sensor, and at steps 32 to 35, the required basic fuel injection amount T _Pi of the cylinder i for which the latest fuel injection is performed is made the final fuel injection amount T _i. Basic fuel injection amount T _P used when setting
Read as.

In step 36, various correction coefficients COFE based on the engine cooling water temperature and the like and a correction amount T _S based on the battery voltage are calculated.

In step 37, the feedback correction coefficient set
Enter the learning correction coefficient K _LRN searched by LAMBDA and another routine.

In step 38, the final fuel injection amount T _i is calculated by the following equation.

T _i = T _P · LAMBDA · K _LRN · COEF + T _{S An} injection pulse having a pulse width corresponding to the fuel injection amount T _i calculated as described above is injected at a predetermined cylinder injection timing as fuel supply means. The fuel is output to the valve 10, and fuel equivalent to T _i is injected and supplied.

Next, a routine for setting various correction coefficients used for the volume efficiency setting will be described.

FIG. 5 shows a routine for setting the energization duty ratio for controlling the opening degree of the idle control valve 19 and estimating the altitude during deceleration. This routine is also executed in the same cycle as the fuel injection amount setting routine, but the phases are shifted (for example, there is a deviation of 5 ms).

In step 41, the ON / OFF signal of the idle switch 8A is input.

In step 42, it is determined whether the idle switch 8A is ON or OFF, and when it is determined to be OFF, the process proceeds to the switch 43 and the idle control valve 1
Establish the auxiliary air flow rate ISC _L passing through 9 to a fixed value according to the operating conditions.

When it is judged to be ON in step 42, the routine proceeds to step 44, where it is judged whether or not it is a condition for feedback controlling the idle speed of the engine (hereinafter referred to as ISC condition). Specifically, the ISC condition is when the engine speed N and the vehicle speed VSP are respectively below a set value and the neutral switch is ON (that is, the neutral position). If this condition is satisfied, go to step 45. Then, the auxiliary air flow rate ISC _L is increased / decreased and set so that the engine speed approaches the target idle speed, and then the process proceeds to step 55.

If the judgment in step 44 is a non-ISC condition of NO, step 4
After proceeding to step 6, the auxiliary air flow rate ISC _BCV for keeping the negative pressure in the intake manifold constant immediately after deceleration (boost control valve function) is set based on the engine speed and the intake temperature, and then proceeds to step 47.

In step 47, an auxiliary air flow rate ISC _E that can maintain stable idle rotation while preventing engine stall is set.

In step 48, the ISC _BCV obtained in step 46 is compared with the ISC _E obtained in step _47.If ISC _BCV ≥ISC _E , the process proceeds to step 49, where ISC _BCV is set as the auxiliary air flow rate ISC _L , and ISC _BCV is set. _{If BCV} <ISC _E , proceed to step 50 and repeat IS
Set C _E as the auxiliary air flow rate ISC _L.

Next, at step 51, the altitude estimation flag FALT
Is 1 or 0, and if it is 0, the process proceeds to step 55 without performing altitude estimation.

If the determination in step 51 is 1, proceed to step 52,
The intake pressure P _BD at the time of deceleration, which is set with reference to the lowland for the engine speed N, is obtained by searching from the one-dimensional map stored in the ROM.

In step 53, the differential pressure DLTBOOST is calculated by subtracting the set deceleration intake pressure P _BD from the intake pressure P _B at the current deceleration operation.

In step 54, the estimated altitude ALT ₀ is searched for from the map of the estimated altitude set for the differential pressure DLTBOOST.

Then, it proceeds to step 55. Step 55, Step
The energization duty ratio ISC _DY of the pulse current output to the idle control valve 19 is searched from the map stored in ROM for the auxiliary air flow rate ISC _L set in any of 43, step 45, step 49, and step 50. Ask for.

The pulse current having the energization duty set in this way is output to the idle control valve 19 at a predetermined cycle,
As a result, the auxiliary air flow rate ISC _L is set according to the controlled opening degree of the idle control valve 19.

FIG. 6 shows a routine for setting the feedback correction coefficient used for setting the fuel injection amount and its average value.
This routine is executed in synchronization with the engine rotation.

In step 61, based on the latest engine speed and the basic injection amount T _P , it is determined from the two-dimensional map stored in the ROM whether or not the operating region is where the air-fuel ratio feedback control is performed.

When it is determined that the operation area is out of the operating range, the routine ends without executing this routine. That is, the feedback correction coefficient is clamped to the current value (or reference value), and the air-fuel ratio feedback control is stopped.

If it is determined that the operation range is set, step 62
Then, based on the engine speed N and the basic injection amount T _B , the proportional component P and the integral component I in the feedback control are obtained by searching the map.

In step 63, the signal voltage V ₀₂ from the oxygen sensor 14 is input, and in step 64, the signal voltage V ₀₂ is compared with the reference voltage V _REF equivalent to the target air-fuel ratio (theoretical air-fuel ratio), thereby making the air-fuel ratio rich.・ Determine lean.

When the air-fuel ratio is lean (V ₀₂ <V _REF ), step 65
Then, it is judged whether or not it is the time of reversing from rich to lean (immediately after reversing), and at the time of reversing, the routine proceeds to step 66, where the current value of the feedback correction coefficient LAMBDA is stored as a, and then the routine proceeds to step 67 to perform feedback Correction coefficient LAMBDA
Is increased from the previous value by the proportional amount P set in step 62.

When not inversion, the routine proceeds to step 68, where the feedback correction coefficient LAMBDA is increased by the integral I set in step 62 with respect to the previous value, and the feedback correction coefficient LAMBDA
Increase MBDA at a constant slope. Note that P >> 1.

When the air-fuel ratio is rich (V ₀₂ <V _REF ), the _routine proceeds from step 64 to step 69, and it is judged whether or not it is the lean to rich reversal, and at the time of reversal, the routine proceeds to step 70 and the current LAMBDA value. Is stored as b, the routine proceeds to step 71, where the feedback correction coefficient LAMBDA is decreased by the proportional amount P set with respect to the previous value. Except at the time of reversal, the routine proceeds to step 72, where the feedback correction coefficient LAMBDA is decreased by the integrated amount I set with respect to the previous value, and thus the feedback correction coefficient LAMBDA is decreased with a constant slope.

In this way, after setting the feedback correction coefficient LAMBDA, the routine proceeds to step 73, where the latest value a at the time of reversal from rich to lean stored at step 66 and the value at the time of reversal from lean to rich stored at step 70. The average value (a + b) / 2 with the latest value b is calculated.

This average value (a + b) / 2 is the feedback correction coefficient
LAMBDA is the control center value.

FIG. 7 shows a small correction coefficient K _FLAT and a learning correction coefficient K _LRN.
2 shows a routine for setting, the altitude estimation, and the learning correction coefficient. Since this routine has the lowest priority,
It is executed as a background job (BGJ).

In step 81, a minute correction coefficient for minutely correcting the basic volume efficiency η _V0 based on the engine speed and the intake pressure.
K _KLAT is retrieved from the 2D map stored in ROM and set.

Here, since the volumetric efficiency is little changed by the change of the engine speed, if the basic volumetric efficiency η _V0 is set for the intake pressure P _B , the correction width is small and it is a value around 1 so that it is very small. The number of grid points (storage capacity) for storing the correction coefficient K _FLAT can be small. Further, since the setting error due to the time delay of the minute correction coefficient K _FLAT is small, it can be executed as BGJ to ensure sufficient accuracy, and the calculation of the minute correction coefficient K _FLAT that requires the calculation time is not required during the transient operation. Therefore, the setting of the fuel injection amount can be updated in a short cycle, the accuracy of air-fuel ratio control is improved, and the transient operation performance is improved.

Although the correction range is small, the intake volume efficiency is a value that changes in the intake pressure changing direction.
As shown in Japanese Patent Publication No. 41230, the function of improving the volumetric efficiency setting accuracy is large as compared with the one in which the correction coefficient is set by the one-dimensional map for the rotation speed.

Next, at step 82, the learning correction coefficient K _LRN corresponding to the current engine speed N and the basic injection amount T _P is searched from the two-dimensional map stored in the RAM.

In step 83, the learning correction coefficient retrieved in step 81
A new learning correction coefficient K _{LRN (news)} is calculated by adding the average value ▲ ▼ of the feedback correction coefficient obtained by the routine of FIG. 6 to K _LRN , and the learning stored in the same area of the RAM is calculated. Correct and rewrite the correction coefficient K _LRN data.

Next, in step 84, it is determined whether the flag FALT for altitude estimation learning is 0 or 1. When FALT is determined to be 0, this routine is terminated without performing altitude estimation learning, but when it is determined to be 1, the process proceeds to step 85 and thereafter,
Set altitude estimation and altitude correction factors.

In step 85, the learning correction coefficient K after the correction is added to the average value ▲ ▼ of the feedback correction coefficient.
The deviation amount Δλ _ALT from the base air-fuel ratio (λ = 1) due to altitude change is calculated by multiplying _{LRN (news)} by the current altitude learning correction coefficient K _ALT .

In step 86, the engine speed N and the basic injection amount T _P are multiplied to calculate the amount Q proportional to the intake air flow rate.

In step 87, the latest altitude data ALT ₀ is obtained from the two-dimensional map based on the Q and Δλ _ALT .

Here, the higher the altitude, the lower the atmospheric pressure, so the exhaust pressure drops, and the residual gas in the cylinder is more easily discharged than in the lowlands, and the filling rate of fresh air increases even with the same intake pressure. Since the air-fuel ratio becomes lean, the deviation amount Δλ _ALT of the base air-fuel ratio becomes large. Further, the smaller the intake air flow rate Q is, the smaller the exhaust pressure is. Therefore, the deviation amount Δλ _ALT becomes large even if the atmospheric pressure is lowered by the same altitude change.

Therefore, in the ALT ₀ map, the estimated altitude ALT ₀ is set to increase as Q increases and Δλ _ALT increases.

At step 88, the latest estimated altitude data ALT ₀ set at step 77 and the past i estimated altitude data ALT ₁ updated and stored by sequentially incrementing the subscript every predetermined period (for example, 10 _S ) in the routine shown in FIG. .. ALT _i and newer weights W _{0 to} W _i (W ₀ + W ₁ + ... W _i = 1) are sequentially added to obtain a weighted average to obtain an average estimated altitude ▲ ▼.

In step 89, the altitude correction coefficient K _ALT is searched for from the two-dimensional map stored in the ROM based on the intake air flow rate proportional amount Q found in step 86 and the average estimated altitude ▲ ▼ found in step 88.

Here, the altitude correction coefficient K _ALT is set as follows. That is, because the atmospheric pressure decreases as the altitude increases, the ratio of fresh air (fresh air ratio) improves even under the same intake pressure conditions as in lowlands, and the air-fuel ratio increases, for the reason explained in step 87. When the intake air flow rate Q is lower, the exhaust pressure is smaller, and the atmospheric pressure is more likely to affect the fresh air ratio.

Therefore, the higher the altitude ▲ ▼, the more
The higher the intake air flow rate Q, the higher the fresh air ratio, so that the altitude correction coefficient K _ALT for correcting the basic volume efficiency η _V0 is set larger.

For altitude correction, it is known that the atmospheric pressure is detected by a pressure sensor or the exhaust pressure is measured to correct the atmospheric pressure, but it is necessary to add a pressure sensor in both cases. There is also one in which one pressure sensor detects not only the intake pressure but also the atmospheric pressure and the exhaust pressure, but a solenoid valve for switching the detected pressure is required, and the control becomes complicated. Further, there is a system in which the intake pressure downstream of the throttle valve before the start is detected as the atmospheric pressure, but it is not possible to deal with the case where the intake pressure starts up on a flat ground and moves to a high altitude. In addition, there is a system in which the intake pressure at the time of full open operation is detected as the atmospheric pressure, but there is almost no detection opportunity when traveling downhill while decelerating. Further, even if the air-fuel ratio feedback control is performed to keep the air-fuel ratio constant, the oxygen sensor becomes inactive during deceleration, or the detected air-fuel ratio is deviated due to the decrease in exhaust temperature, so the accuracy of the air-fuel ratio control does not deteriorate. Inevitably, providing a heater to heat and activate the oxygen sensor is costly.

In this embodiment, the learning correction coefficient K _LRN is used when traveling uphill.
The altitude is estimated based on the differential pressure between the set intake pressure based on the lowland and the actual intake pressure when the vehicle is traveling downhill, because the boost control valve characteristics of the idle control valve are used to estimate the altitude. It is a low-cost configuration that does not require additional hardware, but can always estimate altitude well. Therefore, the altitude correction coefficient K _ALT , which is set based on the altitude, is highly reliable, and thus the volumetric efficiency Q _CYL is set with high accuracy.

Further, when calculating the basic injection amount T _P, the mass filling amount obtained as the product of the intake pressure P _B and the volumetric efficiency Q _CYL is corrected with the intake temperature by the temperature correction coefficient K _TA , and the proportional constant K
Due to so as to set the basic injection quantity T _P as a value obtained by multiplying the _CON, can set the basic injection quantity T _P with extremely high precision. As a result, the accuracy of air-fuel ratio control based on the fuel injection amount T _i set based on the basic injection amount T _P is improved, and stable operation performance can always be ensured.

In the embodiment, the one applied to the one that sets the basic fuel supply amount based on the detected value of the intake pressure is shown, but it is also applied to the one that sets the basic fuel supply amount based on the detected value of the intake air flow rate. it can. In this case, the intake air flow rate correction factor ψ
Should be set for the basic fuel supply amount T _P. This is because the intake pressure P _B and the basic fuel supply amount T _P are substantially proportional to each other. Strictly speaking, the volumetric efficiency Q _CYL is involved between the two as described above, but the change in the volumetric efficiency Q _CYL is the number of revolutions. Since it is small with respect to the change in N, there are 3 regions of low rotation region, medium rotation region and high rotation region.
It is enough to have a street map.

Further, in the present invention, the opening area of the intake system is calculated, but it may be replaced by a volumetric air flow rate that is proportional to this.

<Effects of the Invention> As described above, according to the present invention, the intake air flow rate correction set according to the rate of change in the opening area of the intake system that is variably controlled and the pressure ratio on the upstream and downstream sides of the variable controller. Since the amount of fuel increase / decrease correction during transient operation is set based on the coefficient, good air-fuel ratio control according to the true cylinder intake air amount can be performed for all transient operations, improving transient operation performance. To do.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a configuration diagram showing the configuration of an embodiment of the present invention, and FIGS. 3 to 8 are flowcharts showing various control routines of the same embodiment. FIG. 9 is a diagram showing the characteristic of the intake air flow rate correction coefficient with respect to the intake pressure, and FIG. 10 is a diagram showing the characteristic of the intake air flow rate with respect to the intake system opening area. 1 ... Engine, 9 ... Intake pressure sensor, 8 ... Throttle sensor, 10 ... Fuel injection valve, 11 ... Control unit, 15 ... Crank angle sensor

Claims (1)

[Claims] 1. An operating state detecting means for detecting at least a state quantity relating to intake air, a basic fuel supply quantity setting means for setting a basic fuel supply quantity based on the detected operating state, and an intake air variably controlled. Opening area calculating means for calculating the opening area of the system, opening area change rate calculating means for calculating the change rate of the calculated opening area, pressure P _A on the upstream side of the variable control section of the intake system and downstream side Correction coefficient ψ according to the ratio with the pressure P _{B of} (K: specific heat ratio of air) Intake air flow rate correction coefficient calculation means, based on the calculated opening area change rate and correction coefficient ψ of intake air flow rate, fuel increase during transient operation A fuel correction amount setting means for setting a reduction correction amount; and a fuel supply means for supplying the engine with a quantity of fuel obtained by correcting the set basic fuel supply quantity by the increase / decrease correction quantity. A control device for an internal combustion engine, which is characterized.