JPS6187935A - Air-fuel ratio controller for internal-combution engine - Google Patents

Abstract

PURPOSE:To keep off the rich tendency of an air-fuel ratio at a high load range, by controlling the air-fuel ratio to be turned to the lean side according to a fundamental injection quantity in time of realization of a lean control condition, and a learning compensation value found in time of closed-loop air-fuel ratio control. CONSTITUTION:A fundamental injection quantity TP commensurate to an air-fuel ratio at the rich side is calculated by a fundamental injection quantity operational device A according to specified driving state parameters of engine speed and suction pressure, etc. Next, in the specified driving state, an air-fuel ratio compensation value FAF is calculated by a closed-loop air-fuel ratio controlling device B according to the actual air-fuel ratio, and the fundamental injection quantity is controlled so as to be compensated according to this air-fuel ratio compensating value FAF. At this time, at a learning device C, learning compensation values TAUG and KG are learned so as to cause the FAF to converge within the specified range on the basis of motion of the controlling device B at every engine load state region. And, in time of realization of a lean control condition, the air-fuel ratio is controlled to be turned to the lean side by open loop according to the fundamental injection quantity TP and learning compensation values TAUG and KG by a open loop controlling device D.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an air-fuel ratio control device for an internal combustion engine that utilizes an open-loop lean bar system.

Conventional technology As a lean burn system, one is already known that learns and corrects the basic injection amount using closed loop control, and then multiplies this basic injection amount by a lean correction coefficient in an open loop to control the air-fuel ratio to the lean side ( For example, JP-A-57-26
Publication No. 229). Learning values for performing the above-mentioned learning control are provided for each of a plurality of engine load regions, for example, the idle region and the partial load region. After learning for a certain period of time and learning each learning value, the fuel injection amount is interpolated based on these learning values and is set to an appropriate value for all loads.

Problems to be Solved by the Invention However, according to the above-mentioned conventional method, if the engine load state does not enter both the idle state and the partial load region within a certain period of time after the learning condition is established, the subsequent open loop error will occur. - The air-fuel ratio is not adjusted properly. For example, if the engine load condition persists only in the above-mentioned partial load region during the learning period, the learned value for the idle region will not be obtained, and as a result, if open-loop lean air-fuel ratio control is performed as is, If the engine's air-fuel ratio is not controlled to the desired value and the basic injection amount calculation function is set to the lean side (λ>1), the air-fuel ratio in the high load region will be on the rich side and the exhaust gas characteristics will deteriorate. There is a problem with that.

For example, when performing a hot test such as 10 mode from a cold state of the vehicle when a new canister is installed as in the case of a new car, the exhaust gas test is performed after warming up the vehicle at a constant speed for a certain period of time. Therefore, learning ends during warm-up, and a transition is made to open-loop lean air-fuel ratio control. Furthermore, in this case, the evaporative gas is not adsorbed at all in the new Yanista, and the generation of evaporative gas from the fuel tank during warm-up is almost non-existent due to the relationship between the fuel temperature and the evaporative system. The influence of this is not reflected in learning at all. However, during the open-loop slow-on control from the latter half of warm-up to the end of the 10-mode test, the amount of evaporation generated increases and the air-fuel ratio becomes rich. In other words, when the above-mentioned rich tendency due to the basic injection amount calculation function being set to the lean side is superimposed on this rich tendency of the air-fuel ratio, the air-fuel ratio becomes increasingly rich, and the exhaust gas, especially NOx will increase, and in the worst case, the exhaust gas standard will no longer be satisfied.

Means for Solving the Problems An object of the present invention is to prevent the air-fuel ratio from tending to be rich in a high load region when shifting to lean air-fuel ratio control using an inter-loop during warm-up. It is shown in FIG.

In FIG. 1, a basic injection amount calculation means calculates a basic injection ITP corresponding to an air-fuel ratio richer than the stoichiometric air-fuel ratio in accordance with predetermined operating state parameters of the internal combustion engine. The closed-loop air-fuel ratio control means calculates an air-fuel ratio correction amount FAF according to the actual air-fuel ratio of the engine when the engine is in a predetermined operating state, corrects the basic injection lTp according to the air-fuel ratio correction amount FAF, and adjusts the actual air-fuel ratio of the engine. converge the air-fuel ratio within a predetermined range. The learning means calculates a learning correction amount TAUG for each engine load state region so that the air-fuel ratio correction IFAF converges within a predetermined range based on the operation of the closed-loop air-fuel ratio control means for each engine load state region.

Learn KG. When the engine satisfies the lean control conditions, the non-open loop air-fuel ratio control means controls the basic injection amount T.
The air-fuel ratio of the engine is controlled to the lean side in an open loop according to P and each learning correction amount TAUG.

Effects The effects of the above configuration will be explained with reference to FIG.
It is assumed that the basic injection amount function B is set on the richer side than the basic injection amount function Δ(λ-1) corresponding to the stoichiometric air-fuel ratio. In addition, there are two engine load regions, namely the idle region (
It is assumed that a TAIIGa region) and a partial load region (KG region) are provided. As a result, during closed loop control, 0, for example 4
01u++/h If learning is executed only during warm-up operation,
The basic injection amount changes to a value equivalent to straight line C according to the learning value KG. Therefore, if the lean control condition is satisfied and steady running or acceleration (corresponding to the XSi region) of 40 km/h in the 10 mode is performed in an open loop, for example, , the learned basic injection amount C is on the lean side only in the shaded portion.

Note that if the basic injection amount function is set to correspond to the stoichiometric air-fuel ratio as in the past, the fourth
As shown by straight line B' in the figure, it may be substantially set on the lean side. In this case, if learning is performed only in the KG region, the basic injection amount will change corresponding to straight line C', and therefore,
If the lean control condition is satisfied and lean control is executed in an open loop, in the X region, only the shaded portion will be on the rich side.

Embodiment FIG. 4 is an overall schematic diagram showing an embodiment of an air-fuel ratio control device for an internal combustion engine according to the present invention. In FIG. 4, intake air is supplied to the engine body 1 through an air cleaner 2, an intake passage 3, and an intake manifold 4, while exhaust gas from the engine body I is supplied through an exhaust manifold 5 and an exhaust pipe 6. is discharged. The intake passage 3 is provided with a throttle valve 7 for adjusting the amount of intake air in conjunction with an accelerator pedal (not shown). This throttle valve 7
An idle switch 8 that generates a signal LL indicating whether or not the throttle valve 7 is fully closed is provided on the shaft.
L is supplied to the input/output interface 101 of the control circuit 10. Further, a pressure sensor 9 for detecting the absolute pressure of intake air in the intake passage 3 is provided in the intake passage 3 downstream of the throttle valve 7, and its output is sent to the control circuit 1.
0 is supplied to the A/D converter 102 with a built-in multiplexer. Further, the intake passage 3 is provided with a fuel injection valve 11 for supplying pressurized fuel from a fuel supply system to the intake port of each cylinder.

The intake manifold 4 is provided with an intake temperature sensor 12 for detecting the temperature of intake air, and its output THA
is supplied to the A/D converter 102 of the control circuit 10.

In addition, a water temperature sensor 13 is installed in the water jacket of the cylinder block of the engine body ■ to detect the temperature of the cooling water.
is provided, and this output THW is output from A of the control circuit 10.
/D converter 102.

An electric signal is generated in the exhaust manifold 5 of the engine according to the concentration of oxygen components in the exhaust gas. Two sensors 14 are provided. That is, the 02 sensor 14 outputs a binary output voltage that differs depending on whether the air-fuel ratio is on the lean side or the lean side with respect to the stoichiometric air-fuel ratio.
Occurs on 01.

Furthermore, the exhaust manifold 5 downstream of the 02 sensor 14 contains three harmful components HC, Co, and NoX in the exhaust gas.
A three-way catalytic converter 15 is provided to purify the water at the same time.

A distributor (not shown) has a crank angle sensor 16 whose shaft generates a pulse signal for detecting a reference position every 180 degrees in terms of crank angle, and a pulse signal for detecting angular position every 30 degrees in terms of crank angle. A crank angle sensor 17 is provided that generates. Pulse signals from these crank angle sensors 16 and 17 are supplied to an input/output interface 101 of the control circuit 10, and the output of the crank angle sensor 17 is supplied to an interrupt terminal of the CPU 103.

A pulse signal is generated from the output shaft angle sensor 18 every time the final output shaft of a transmission (not shown) rotates by a predetermined angle, and is supplied to the human output interface of the control circuit 10. This pulse signal allows the vehicle speed SPD to be known.

The evaporation system includes a fuel tank (not shown), a throttle body canister 19, and a verge port 20 formed in the throttle body. Also, the canister 19 has check valves 191, 192, 1
93, and activated carbon 194 that adsorbs evaporation. When the fuel tank is full, the check valve 191 is closed when the internal pressure of the fuel tank is negative in order to prevent fuel from leaking from the canister 19 and to prevent damage to the fuel tank due to changes in fuel tank internal pressure caused by changes in fuel temperature. is opened, and when the internal pressure of the fuel tank is positive, the check valve 192 is opened. Furthermore, in order to prevent damage to the canister or the vehicle due to backfire, when the throttle valve 7 is opened and negative pressure is generated in the verge port 20, the evaporated air adsorbed on the activated carbon 194 is sucked into the engine body 1. Therefore, check valve 193 is activated.

The control circuit 10 is configured as a microcomputer, for example, and includes an input/output interface 101, an A/D converter 102, a CPU 103, a ROM 104,
A RAM 105, a backup RAM 106, a clock generation circuit 107, and the like are provided. 108 is a drive circuit for driving the fuel injection valve 11. In addition, the CPU
The interrupt 103 occurs when the A/D converter 102 finishes A/D conversion, when the input/output interface 101 receives a crank angle sensor pulse signal, when an interrupt signal from the clock generation circuit 107 is received, etc. be.

ff127. ! The intake pressure data PM of the sensor 9, the intake temperature data TIIA of the intake temperature sensor 12, and the water temperature data T11- of the water temperature sensor 13 are collected at predetermined time intervals A.
/Di conversion routine is taken in and stored in a predetermined area of the RAM 105. That is, the data PM, THA, and THW in the RAM 105 are updated at predetermined intervals.

Moreover, the rotational speed data Ne is 3 of the crank angle sensor 17.
It is calculated by an interrupt every 0° CA and stored in a predetermined area of the RAM 105.

The operation of the control circuit shown in FIG. 4 will be explained with reference to FIGS. 5 to 8.

FIG. 5 shows a fuel injection amount calculation routine, which is executed at every predetermined crank angle, for example, 180'cA.

In step 501, the intake air pressure data PM and rotational speed data Ne are read from the RAM 105, and the RO old 04
The basic injection amount TP is calculated by interpolation using the two-dimensional map M shown in Table 1 stored in .

Below is the margin Table 1 However, the unit of PM is mmHH, the unit of Ne is rpm, and the values in Table 1 are converted to the reciprocal of the excess air ratio λ to make it easier to understand. Therefore, the values in Table 1 is set to an air-fuel ratio richer than the stoichiometric air-fuel ratio. In addition,
Conventionally, the basic injection amount TP was set to correspond to the stoichiometric air-fuel ratio, as shown in Table 2.

In step 502 of Table 2, the fuel injection iT is determined as T← (TP)TAUG) ・ (1+KG) ・
Calculate by FAF - FLEAN · α + β. Here, TAUG and KG (actually 1+KG as a whole) are a learning correction amount and a learning correction coefficient, respectively. That is, TAUG is a learning correction amount during idling calculated by the routine shown in FIG. 7, which will be described later, and KG is a learning correction coefficient during partial load calculated by the routine shown in FIG. 7. In addition, FAF is the air-fuel ratio correction coefficient calculated by the routine shown in FIG. 6, and FLEAN is the 8th
The lean correction coefficient calculated by the routine shown in the figure, and α.

β is another correction coefficient or correction amount, and corresponds to, for example, warm-up increase correction, intake temperature correction, transient correction, power supply voltage correction, etc.

In step 503, the fuel injection iT calculated in step 502 is entered into a counter built in the drive circuit 108 of the control circuit 10, so that the fuel injection valve 11 is activated for a time T.
will be energized.

Then, in step 504, the routine of FIG. 5 ends.

The air-fuel ratio feedback control, that is, the air-fuel ratio FAF calculation will be explained with reference to the routine shown in FIG. The routine shown in FIG. 6 is executed at predetermined time intervals. In step 601, it is determined whether a closed loop (feed puncture) condition for the air-fuel ratio is satisfied. The closed loop condition is not satisfied during engine startup, during fuel increase operation after engine start, during heating increase operation, during power increase operation, lean control, etc., and in other cases, the closed loop condition is established. If the closed loop condition is not satisfied, the process advances to step 609 and FAF=1.
Set to 0. If the closed loop condition is satisfied, step 602
Proceed to and perform air-fuel ratio feedhack correction.

In step 602, the output value of the 0□ sensor 15 is taken in to determine whether the air-fuel ratio is rich or lean. When it is lean, it is determined in step 603 whether or not it is the first lean, that is, it is determined whether or not it is a change point from rich to lean. As a result, if it is the first lean, step 60
In step 5, skip IA is added as FAF - FAF + A, and on the other hand, if it is not the first lean, in step 606, a predetermined amount a is added as FAF4 - FAF + a.

Note that the skip amount A is set to be sufficiently larger than a. That is, A>>a.

In step 602, if rich, step 60
Proceed to step 4. In step 604, it is determined whether or not it is the first rich state, that is, it is determined whether or not it is a change point from lean to rich. As a result, if it is the first rich, step 60
In step 7, skip iB is subtracted as FAF←FAF-B. On the other hand, if it is not the first rich, the process proceeds to step 608, and a predetermined amount is subtracted as FAF4-FAF-b. Note that the skip amount B is set to be sufficiently larger than b. That is, B>>b.

In other words, the control shown in steps 606 and 608 is called integral control, and the control shown in steps 605 and 607
The control shown in is called skip control.

The process proceeds to step 610 only when skip control is performed. In step 610, it is determined whether the conditions for performing learning are satisfied. In other words, the cooling water temperature THW is 8
It determines whether the temperature exceeds 0℃, determines whether the intake air pressure PMA is higher than 650 mm 11 g, and determines whether the vehicle speed
It is determined whether the rate of change ΔSPD/2s is lower than 0.7 Km/h, and the intake air temperature THA is 40℃<THA<90
It is determined whether the temperature is within the range of ℃. In addition, PMA
is throttle opening of 50° or more and Ne≦2000rpm
The state of is the intake air pressure taken in after IS has elapsed. As a result, THW>80℃, PMA>650mm1g
, ΔSPD/2s< 0.7 Km/h, and 40
℃<THA<90°C, it is assumed that the learning execution condition is satisfied, and the process proceeds to step 611. If the learning execution condition is not satisfied, the process proceeds to step 612, and the learning routine shown in FIG. 7 is executed.

The air-fuel ratio correction coefficient FAF calculated in steps 606 to 609 is stored in the RAM 105 in step 612,
At step 613, the routine of FIG. 6 ends.

FIG. 7 shows the learning routine that is step 611 in FIG. This learning routine calculates the learning correction amount TAUG and the learning correction coefficient KG, and is executed at the skip time as described above. In step 701, an average value FAFAV of the air-fuel ratio correction coefficient FAF is calculated. Here, the calculation is performed using the arithmetic average value of the value FAFO at the time of the previous skip and the value FAF at the time of the current skip.

That is, the calculation of FAFAV-(PAFO+FAF)/2 is performed. Next, in step 702, FAFAV is 0.9.
It is determined whether the value is within the range of 5 to 1.05.

As a result, oJ5≦FAFAv≦t, osno and kini proceed to step 719, and the learned values TAUG and KG are both unchanged), but FAFAV < 0.95.
Or, when FAFAV > 1.05, the learned value TAUG or K depending on whether it is idle or part load.
G is changed. Note that here, idle time is defined as when the idle switch 8 is on (LL="l"), and when the idle switch 8 is on (LL="l").
<1100 Orp and P M >200 mmH
Partial load is defined as when the idle switch 8 is off (LL = "0") and the temperature is 200 mmHg.
< P M < 400 mml (defined as when g is satisfied.

Therefore, when FAFAV<0.95 and when idle, the flow moves to steps 703, 704, 705.
, 706, the idle learning value TAUG is subtracted by a predetermined amount -8, and in step 706, the TAUG is stored in RAM1.
05, and when FAFAV<0.95 and at partial load, the flow goes to step 703.70.
8. Proceed to 709, and the partial page loading learning value KG is set to the predetermined value ff1.
-0.002 is subtracted, and in step 710 KG is RA
It is stored in M105.

Similarly, when FAFAV > 1.05 and when idle, the flow continues through steps 711, 712, 713.
．． In step 714, the idle learning value TA[IG is added by a predetermined amount +8, and in step 715, TAUG is set to RAM1.
05, and when FAFAV > 1.05 and at partial load, the flow goes to step 711,
The process proceeds to steps 716 and 717, where the partial page load learning value KG is added by a predetermined amount +0.002, and in step 718, KG is set to II.
It is stored in AM105.

Then, in step 719, preparation is made for the next execution as FAFO-FAF, and in step 720, this routine ends.

Next, an example of calculation of the lean correction coefficient FLEAN in lean control will be explained with reference to FIG. first,
In step 801, it is determined whether lean control conditions are satisfied. This means that all conditions such as being below this lean control are satisfied.

When it is determined that the lean control condition is satisfied, the process proceeds to step 802, and when it is determined that the lean control condition is not satisfied, the lean correction coefficient F is determined in step 807.
In step 802 where LEAN is set to 1, it is determined whether the throttle valve 7 is open by determining whether the idle switch 8 is off, and when the idle switch 8 is off, (LL=" 0″) is stored in the RAM 105 in step 803.
The intake pressure data PM and the rotational speed data Ne are read out from the lean correction coefficient FI stored in the ROM 104.
Interpolate the lean correction coefficient FLEAN from the JAN map. On the other hand, when lean control is not in progress, the vehicle speed SPD is set to a predetermined value (
For example, it is determined whether the speed exceeds 10 km/h), and if the speed exceeds a predetermined value, the routine ends at step 808. On the other hand, when the vehicle speed SPD is below a predetermined value, that is, when starting, the lean correction coefficient F is determined in step 807.
Set LEAN to 1 and cancel lean control.

When the idle switch 8 is on (LL = "1"), the engine rotation speed N within a predetermined time is determined in step 809.
The average value NAV of e is determined, and in the next step 810 it is determined whether the average value NAV exceeds a predetermined value B (for example, 600 rpm). When the average value NAV is less than the predetermined value B, the lean control is stopped in step 807, and the average value NA
When V exceeds the predetermined value B, lean control is performed in step 811 by setting the lean correction coefficient F LIE A N to a predetermined value less than 1 (for example, 0.92), and in step 8
This routine ends at step 12.

As described above, even if the basic injection amount calculation function is set to the rich side, the air-fuel ratio does not matter under normal operating conditions. In other words, under normal driving conditions, the vehicle is considered to be operating in all load ranges, including the idle range, partial load range, etc., and therefore, sufficient learning is not performed in the multiple set learning ranges. This is because it can be considered as something that exists. In other words, this means that no matter what basic injection amount calculation function is set, if learning control is performed sufficiently, the basic injection amount will be the stoichiometric air-fuel ratio.

As described in detail, according to the present invention, the basic injection amount calculation function is created using the Lynch air-fuel ratio equivalent (λ<1).
While sufficient learning occurs in the KG learning region, learning remains insufficient in the TAUG learning region, and when shifting to open-loop lean control, the air-fuel ratio in the high load region becomes lean as shown in FIG.

In particular, when conducting an exhaust gas test, as shown in Figure 9,
After warming up the vehicle at approximately 40 km/h for 15 minutes, a 10-mode test (6 cycles) is performed. At this time, feedback control (closed loop control) is performed while the vehicle is warming up, and learning is executed when learning conditions are met.On the other hand, in the 10-mode test, lean control is executed when lean control conditions are met.

However, when the vehicle is warmed up, learning control in the idle region is not performed, so TAUG learning is not performed, and only KG learning control in the partial load region is performed. As a result, in the present invention, since the basic injection amount calculation function (map) is set on the rich side, it becomes on the lean side in the high load region, as shown in FIG. Therefore, when performing the above exhaust gas test on an engine with a new canister, since such a test starts from a cold state, both the fuel temperature and tank pressure are low at the beginning, so it is difficult to warm up the vehicle. There is almost no evaporation generation inside the tank, and as the test progresses, both the fuel temperature and the tank internal pressure rise, and the amount of evaporation generation increases.When the tank internal pressure exceeds the set pressure of the check valve 192, the check valve 19
2 opens, and the evaporator is adsorbed into the canister 19, and is also sucked into the engine body 1. However, the learning is completed and the influence of the evaporator is not reflected at all, but it is possible to prevent the air-fuel ratio from changing. Therefore, it is possible to prevent the increase in the exhaust gas, especially the NOx component, as shown in FIG. 10.

Of course, if a used canister is used, evaporation will occur even while the vehicle is warming up, so although the shadow of the evaporation is only in a part of the load area, it will be reflected in the learning, so there is no particular problem. . Moreover, the basic jet view setting function of the present invention is the first
It goes without saying that the lean limit (misfire limit) shown by diagonal lines in Figure 0 should be taken into consideration when determining the lean limit.

[Brief explanation of drawings]

FIG. 1 is an overall block diagram for explaining the present invention in detail, FIGS. 2 and 3 are graphs for explaining the present invention in detail, and FIG. 4 is an air-fuel ratio control device for an internal combustion engine according to the present invention. An overall schematic diagram showing one embodiment; FIGS. 5 to 8 are flowcharts for explaining the operation of the control circuit in FIG. 4; FIG.
FIG. 10 is a graph illustrating the present invention in detail. 1: Engine body, 7: Throttle valve, 8: Idle switch, 9: Pressure sensor, IO = control circuit,
14: Oz sensor, 19: Epposition system. (@) ← Load → (High) (Light) ← Load → (High)

Claims (1)

[Claims] 1. A basic injection amount calculation means for calculating a basic injection amount corresponding to an air-fuel ratio on the richer side than the stoichiometric air-fuel ratio according to predetermined operating state parameters of the internal combustion engine; Closed-loop air-fuel ratio control means that calculates an air-fuel ratio correction coefficient according to the actual air-fuel ratio, corrects the basic injection amount according to the air-fuel ratio correction coefficient, and converges the actual air-fuel ratio of the engine within a predetermined range. , learning a learning correction amount for each of the plurality of engine load condition regions so that the air-fuel ratio correction amount converges within a predetermined range based on the operation of the closed-loop air-fuel ratio control means for each of the plurality of engine load condition regions; an internal combustion engine, comprising: a learning means; and an open-loop air-fuel ratio control means for controlling the air-fuel ratio of the engine to a lean side in an open loop according to the basic injection amount and each learning correction amount according to lean control conditions of the engine. Engine air-fuel ratio control device.