JPS61232364A - Surging controller for internal-combustion engine - Google Patents

Abstract

PURPOSE:To improve drivability ever so better, by comparing a signal level in response to variations in an engine combustion state in a steady state of an engine with the specified value and, when it is judged as surging with this comparison, having an engine driving condition factor controlled in a surging checking direction. CONSTITUTION:During engine driving, output of a lean sensor 6 is stored in a read-only memory 10f after being made into analog-to-digital conversion, and an absolute value S in a difference between this time and the last output values of the lean sensor 6 is calculated by a central processing unit 10d. Next, it is left intact unless the value S is less than zero but if being below, it is set to zero, and the value S is added to an integral quantity DELTALN. Next, that whether an engine is in a steady state or not is discriminated, and when YES is discriminated, a mean value of the DELTALN for several portions so far is found, and this mean value is set down to a surging level. Then, this level is compared with the specified value, and when it exceeds the specified value, it is judged as surging whereby an engine driving condition factor, for example, a fuel injection valve 11 is controlled in a surging checking direction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a surging control device suitable for an internal combustion engine using a lean burn system.

[Prior art]

In recent years, lean burn systems have been adopted in which internal combustion engines are operated at a lean air-fuel ratio to prevent exhaust pollution and to reduce fuel consumption. That is, there is a system in which a lean sensor is provided in the exhaust pipe of the engine, and the output signal of the lean sensor is used to feedback-control the air-fuel ratio of the engine to an arbitrary value on the lean side.

[Problem that the invention seeks to solve]

In such a lean burn system, an air-fuel ratio that does not have enough margin for the misfire limit is adopted for the purpose of reducing NOx emissions, and therefore, considering the worst-case tolerance of the lean sensor's durability, misfires and surging may occur. This may lead to deterioration of driving performance. An object of the present invention is to provide a surging suppression device in a lean burn system.

[Means for solving problems]

As shown in FIG. 1, the surging control device of the present invention includes means A for generating a signal in accordance with fluctuations in the combustion state of an internal combustion engine.
, a steady state determining means B for determining whether the engine is in a steady state, a means C1 for comparing the signal level from the signal generating means A in the steady state of the engine with a predetermined value, and at least one engine when surging is determined by this comparison. It consists of means for controlling operating condition factors in a direction that suppresses surging.

〔Example〕

The present invention will be described in detail with reference to the drawings from FIG. 2 onwards.

In FIG. 2, which is an overall schematic diagram of an internal combustion engine according to the present invention, a combustion chamber 1' within an engine body 1 is connected to a surge tank 3 via an intake passage 2. As shown in FIG. A pressure sensor 4 for detecting the absolute pressure of intake air in the intake passage 2 is provided in the surge tank 3, and its output is supplied to an A/D converter 10a with a built-in multiplexer of a control circuit 10. There is a line (mixture) in the exhaust passage 5 connected to the combustion chamber 1'.
A sensor 6 is provided. From lean sensor 6, the third
As shown in the output characteristics in the figure, a current output is obtained according to the air-fuel ratio. The current-voltage conversion circuit 10b of the control circuit 10 performs voltage conversion and supplies the voltage to the A/D converter 10a.

The distributor tough has a crank angle sensor 8 whose shaft generates a reference position detection pulse signal every 720' in terms of crank angle, and a crank angle sensor 8 which generates a pulse signal for angular position detection every 30 degrees in terms of crank angle. A crank angle sensor 9 is provided. Pulse signals from these crank angle sensors 8 and 9 are supplied to an input/output interface 10c of a control circuit 10.

Further, the intake passage 2 is provided with a fuel injection valve 11 for supplying pressurized fuel from a fuel supply system to the intake boat for each cylinder.

The control circuit 10 is configured as a microcomputer, for example, and includes a CP
U10d, ROM10e.

A RAM 10f is provided. 10g is fuel injection valve 1
This is a drive circuit for driving 1. In addition, CPU1
The interrupt 0d occurs when the A/D converter 10a completes A/D conversion, when the input/output interface IOC receives pulse signals from the crank angle sensors 8 and 9, and the like.

Intake pressure data PM of the intake pressure sensor 4 and output current value 1 of the engine sensor 6. is fetched by an A/D conversion routine executed at predetermined time intervals and stored in a predetermined area of the RAM 10f. In other words, PM in RAMI Of,
I. Data is updated at predetermined intervals.

FIGS. 4(A) and 4(B) are timing diagrams for explaining the principle of surging measurement in the embodiment of the present invention.

When the vehicle is traveling at a constant speed and the air-fuel ratio is relatively richer than the misfire limit, the output signal waveform of the lean sensor 6 hardly changes as shown in FIG. 4(A). On the other hand, when the air-fuel ratio approaches the misfire limit while driving at a constant speed, the output signal waveform of the lean sensor 6 has a part that protrudes toward the lean side, as shown in Figure 4 (B). do. In other words, the present invention detects surging by identifying the difference in the change in the output waveform of the lean sensor, and when surging is detected, the fuel injection amount, injection timing, ignition timing, E
It controls the GR amount, water temperature, and other engine operating condition factors.

First, the operation of the apparatus shown in FIG. 2 when the present invention is implemented by injection timing control will be explained with reference to the flowcharts shown in FIGS. 5 to 9.

FIG. 5 shows an A/D conversion routine as a surging detection routine, which is part of the main routine and is executed every predetermined period of time, for example, every 12 m5. That is, in step 501, the output value LNS of the lean sensor 6 is
R is fetched from the A/D converter 10a and stored in the RAM 10f. At this time, other A/D converted values such as intake pressure data PM are also taken in from the A/D converter 10a and R
It is stored in AM10f.

In step 502, the previously captured output value LNSRO of the lean sensor 6 and the current output value LNSI? The absolute value S of the difference is calculated. In other words, S ←l LNSR−L
NSROl - However, -1 is for eliminating the change in the output value LNSR of the lean sensor 6 due to air-fuel ratio feedback as a dead zone. Therefore, -1 is not necessarily necessary. In steps 503 and 504, if S is less than or equal to 0, it is left as is, and if it is less than or equal to S, it is set to O and is guarded with 0. In step 505, the value S is added to the integrated amount ΔLN.

In step 506, it is determined whether or not a steady state exists.

Conditions for a steady state include, for example, that the current air-fuel ratio A/F is above a predetermined value, that the engine rotation speed Ne is within a predetermined range, that the intake pressure PM is within a predetermined range, and that the change in intake pressure PM is For example, it must be within a predetermined range. As a result, if the state is not steady, the process proceeds to step 510 and the timer counter T is cleared.

Note that the timer counter T is, for example, a 32 ms counter, and in this case measures the duration of the steady state. After step 510, the process advances to step 511 to clear the integrated amount ΔLN, and in step 512, the LNSR is set to LNSRO to prepare for the next execution, and in step 513
This routine ends.

If it is before 0.53 has elapsed since the steady state has been reached, the process advances from step 506 to step 507, and then to step 511. That is, since the timer counter T is not cleared, the measurement of the duration of the steady state continues.

Next, when 0.53 elapses after the steady state is reached, the process proceeds from step 506 to step 512 through steps 507 and 508. In other words, since the integrated amount ΔLN is not cleared, integration of the absolute value S calculated in step 502 is started.

Further, when 1.58 hours have passed since the steady state has been reached, the process proceeds from step 506 to step 509 via steps 507 and 508, and calculates ΔLN←(ΔLNX 15+ΔLN)/16. Here, ALN indicates the average value of ALN for the past 15 times. In other words, the value ΔLN calculated this time is
It will be revised in 2009.

From the above, the following can be understood. That is, the signal from the lean sensor represents a change in the combustion state, and its integrated value ΔLN represents the surge engine level. That is, Δ
If the combustion fluctuation is small as shown in Fig. 4 (A), N becomes (C
), the integrated value increases slowly, as shown by the dashed-dotted line, while (B)
If the combustion fluctuation is large, as shown in (C), the integrated value increases rapidly, as shown by the solid line in (C). Therefore, the magnitude of surging can be determined by the magnitude of ALN. Then, by taking the smoothed average ΔLN, the past history can be reflected in the measured value of the surge level.

In the routine of FIG. 5, even if 0.53 has elapsed since the steady state, if the unsteady state occurs before 1.53 elapses, the flow at step 506 proceeds to step 510, so the initial state is Return to

FIG. 6 shows an injection amount calculation routine, which is executed at every predetermined crank angle. For example, if it is a synchronous injection method, 36
It is executed at a predetermined crank position every 0° CA, and in the case of a 4-cylinder independent injection system, it is executed at a predetermined crank position every 180' CA. In step 601, intake pressure data P
The basic injection amount τp is calculated according to M and the rotational speed data Ne, and in step 602, the final injection amount τ is calculated using the following equation by incorporating the feedback correction coefficient FAF and the lean correction coefficient KLEAN. That is, τ←τ, −F
AF・(KLEAN+α)・β+T However, α, β, γ
: Correction amount calculated based on other operating state parameters. This routine then ends at step 603.

Referring to the routine in FIG. 7, calculate the lean correction coefficient KLEAN.
The calculation of is explained. In step 701, KLEANPM is calculated from the one-dimensional map based on the intake pressure data PM.
In step 702, KLEANNE is calculated from a one-dimensional map based on the rotational speed data Ne, and in step 703, KLEAN=KLEAN
PM・KLEANNI! Calculate. Calculated KLE
The AN is stored in the RAM 107 in step 704, and the routine ends in step 705. In other words, the lean air-fuel ratio correction coefficient is for setting the air-fuel ratio to the lean side.

An outline of the FAF calculation will be explained with reference to the routine shown in FIG. The routine of FIG. 8 is executed at predetermined time intervals. In step 801, it is determined whether a feedback condition is met. The feedback conditions include various conditions such as startup, cooling water temperature, etc. If it is not a feedback condition, step 8
Proceed to 02 and set FAF←1. Conversely, if the feedback condition is met, the process proceeds to step 803 and subsequent steps to perform air-fuel ratio feedback correction.

In step 803, the output current value of the lean sensor 6 is 1.
It is determined whether or not is equal to or greater than the reference value 11.

If I≧8, that is, when the air-fuel ratio is leaner than the predetermined lean air-fuel ratio, in step 804, FAF increasing integration processing is performed, and as is well known, FAF is gradually increased. If it is a change point from the lean side to the rich side, well-known skip processing is performed. Further, in step 803, if I<1, that is, if it is richer than a predetermined lean air-fuel ratio, the process proceeds to step 805, where FAF reduction integration processing is performed, and as is well known, FAF is gradually reduced. Ru. Skipping occurs at the transition point from the rich side to the lean side.

FIG. 9 shows the fuel injection routine. In 901, the injection start timing TI as crank angle data is calculated from the engine speed Ne and the intake pressure PM.

In step 902, one stroke of the smoothed average value of the surging signal calculated in step 509 in FIG. 5 is set to a predetermined value C1.
It is determined whether the value is greater than or not. 90 for surging
Proceeding to step 3, the TI plus the correction value is set as the TI. The next step 908 is to input the target surging level Co into ALN. If ALN<C4, proceed to 904 and ΔL I
If c < Ct, 905 converts TI to K t (<
TI is obtained by subtracting K r ). 906.9
In 07, from the injection timing TI calculated by the crank angle,
At that crank angle, the injection start time t1 and the injection end time 1t are calculated so that the injection time is τ in FIG. When set in the second comparator register, the first. The value of the second comparator register is subtracted and typed up at predetermined time intervals. At this time, the injection start and end flags are set, the injection execution routine is executed, and as a result, fuel injection is executed. FIG. 10 shows the timing of the above fuel injection timing control. That is, the injection timing TI is calculated as the crank angle from the bottom dead center BDC (see Fig. 10).
stomach)). Time t corresponding to the crank angle of TI.

is calculated from the rotational speed signal Ne, and the time t after the injection period τ
2 is calculated. The injection pulse rises between tl and t2.

FIG. 11 and FIG. 12 explain the surging suppressing effect according to the first embodiment described above. In other words, the surging level (
ALN), injection timing (TI), and NOx emissions are
The relationship is as shown in Figure 1, and the level of surging can be reduced by delaying the injection timing. (In Fig. 11, the relationship is obtained when the rotation speed, load, and air-fuel ratio are constant.) The signal from the lean sensor 6 is integrated repeatedly in 1.0S increments of 0.53 as shown in Fig. 12 (a). Returned A
LN is obtained (Figure 12 (a)). Smoothed average ΔLN
is executed at every end point of ALN integration, that is, every 1.53 (
Figure 12 (b)). If the allowable value C5 is exceeded, the injection timing will be 1.
The retard amount is retarded by 1 from the level of , and reaches the level of 2 (c). If ALN is 02 or less, the retard amount is decreased by 2, and reaches the level of 3. ALN is still 02
Since it is below, the retard amount is further reduced to 2, reaching a level of 4. As a result, ALN is at surging tolerance level C
, -C2.

In the first embodiment, when the surging level C8 is exceeded, the retardation amount is increased to , and when the surging level reaches below the allowable level 02, the retardation amount is decreased by 2. .11.12).

Alternatively, the correction amount 2 can be set to a constant value. In this case, as shown in Fig. 13, when the surging level is greater than the allowable value CI, the retard amount is increased by K increments like m, and when the surging level becomes less than the allowable value C2, the retard amount is decreased by K. .

FIG. 14 shows a flowchart in another embodiment of injection timing control. Figure 9 means 901°906.907,
908 is the same, but steps 909 to 912 are different. In this embodiment, a constant surging level CA is set, and the surging level, which is the smoothed average value ΔLN of the lean sensor signal, is compared with this constant value CA, and this difference ΔLN-CA=D (referred to as surging degree) is It is determined whether the absolute value 1ΔLN-Cat is larger than a predetermined value S. When the absolute value of D is greater than S, the flow goes to 910, and a correction value K is generated according to the difference. are arranged in a map as shown in FIG. 15, and the correction value corresponding to the current surging degree value is calculated to be 0. In step 912, 0
The injection timing is the sum of TI and TI.

If the surging level deviates from the predetermined value CA to a larger side, the injection timing retard amount will increase, and conversely, if the surging level deviates from the predetermined value CA to a smaller side, the retard amount will become smaller, and the surging level will be at an acceptable level. There is Co,! : Maintained between ct. The KO map shown in FIG. 15 can be a map that incorporates factors other than the surging degree, such as rotational speed, load, water temperature, and the like.

Although the first embodiment described above is a case in which surging is suppressed by controlling injection timing, the present invention also includes surging control by controlling other operating condition factors related to engine combustion. In the second embodiment, the fuel injection amount is controlled by a surging signal. That is, when surging is detected, the injection amount is increased to suppress surging. Although there are various ways to increase the fuel injection amount, an example in which the lean correction coefficient KLEAN is changed will be explained below. In this case, the program shown in FIG. 5 and FIGS. 7 and 8 are the same as those in the first embodiment, but the injection amount calculation routine in FIG. 6 is changed as shown in FIG. 17. 6 in Figure 17
Processes 04 to 60B are added to FIG. In 604, it is determined whether the lean sensor signal smoothed average value ΔLN, which is an index of surging, is greater than or equal to a predetermined value C8. If YES, the process proceeds to 605, where the lean correction coefficient KLEAN is increased by 3. At 606, the average value of the target values (
C:l+C4)/2 is entered. On the other hand, when ΔLN becomes smaller than the predetermined value C4, 604 is passed through 607, and 60
8, and the lean correction coefficient KLEAN becomes smaller by 4. In this way, as the surging level increases, the lean correction coefficient becomes thicker (as a result, the fuel injection amount calculated in step 602 becomes larger, which suppresses surging. As a result, when the surging level decreases, the lean correction coefficient becomes thicker). The coefficient KLEAN becomes smaller and the fuel injection amount τ becomes smaller. Such feedback control suppresses surging.

C3, C4, Kx, and 4 are values selected to provide appropriate surging control. The range of change is the 12th.
13. The settings are the same as in Figure 15.

The third embodiment suppresses surging by controlling the ignition timing. In FIG. 2, an igniter 21 has an ignition circuit and an ignition coil, and the ignition coil is connected to the ignition plug 20 via a distributor 7. On the other hand, the ignition circuit is connected to the I10 circuit 10C. FIG. 18 shows a flowchart of the ignition routine. This routine is a crank angle interrupt routine that is executed at a predetermined crank angle for each cylinder. At step 1801, the basic ignition timing θBAs is determined according to the engine speed NE and intake pressure PM.
The calculation of E is performed. When the KT ball indicating the surging level is larger than the predetermined value C2, the process flows from 1801 to 1802, and the ignition timing is increased by the retardation correction amount δθ.

1802' is the average value of the target value (cs+Ch)/
2 can be entered. When the surging level drops below C5 (C7), the signal changes from 1801 to 1803 to 1804.
The flow is reduced by Δθ. In step 1805, the ignition timing θ is determined by subtracting Δθ and other correction amounts δ unrelated to the present invention from θ8^. In step 1806, the igniter set time t3 is calculated,
It is set in the compare register of the CPU 10d. Further, in step 1807, the igniter reset time t,
is calculated and set in the conveyor register of the CPU 10d.

The ignition signal rises at time t, the ignition signal falls at time t4, and the time of this fall is 1805.
This calculation is performed so that the crank angle θ calculated in step . FIG. 19 illustrates the timing relationships. θ is measured from top dead center TDC, and the crank angle θ
1. from charging time Q and rotational speed NE so that the ignition signal falls at time t4 corresponding to . ．． 14 is calculated.

In this embodiment, when the surging level is large, the ignition timing retard is increased, and as a result, when the surging level decreases, the ignition timing retard amount is reduced, and by repeating such feedback, surging can be suppressed. .

The c, Ca, Ks, and KbO values in Figure 18 are quantities that should be determined so that the surging level falls within the initial range, and the range of change can be set as shown in Figures 12, 13, and 15. can.

In the fourth embodiment, the EGR amount is controlled by a surging signal. In FIG. 2, an EGR passage 22 is provided to connect the exhaust passage 5 and the intake passage 2, and an EGR valve 23 is disposed on the EGR passage 22. The EGR valve 23 is connected to a negative pressure actuator 24, and the negative pressure actuator 24 is selectively communicated with a negative pressure port 27 of the surge tank 3 or an atmospheric filter 28 by a solenoid valve 26.

When the solenoid valve 26 is excited, negative pressure enters the actuator 24, so the EGR valve 23 moves in the opening direction, and the solenoid valve 2
When the EGR valve 6 is demagnetized, the actuator 24 becomes atmospheric pressure, so the EGR valve 23 moves in the closing direction.

Therefore, the duty ratio of the drive signal of the solenoid valve 26, that is, the excitation period X of the solenoid valve 26 for one period of the drive signal
EGR according to the duty ratio (Figure 20), which is the ratio of
The opening degree of the valve 24 is changed (FIG. 21).

FIG. 22 is a flowchart showing a driving routine for the EGR valve 23, and this routine is executed at predetermined intervals. In step 2201, EGRfiEQ is calculated from the rotational speed NE and intake pressure PM. Surging level Δ
When LN is larger than the predetermined value C7, 220 than 2202
3 and is reduced by the EQ. In 2203', the average value of the target values (t, t+cs)/2 is entered into ΔLN.

On the other hand, if the surging level becomes smaller than the predetermined value C3, 2
The signal flows from 202 through 2204 to 2205, and the EQ is increased by 8. In step 2206, a duty signal corresponding to the EQ is applied to the solenoid valve 26. Therefore, E.Q.
An EQR amount corresponding to the amount can be obtained.

In this embodiment, when the surging level is large, the EGR
The reduced amount stabilizes combustion and results in lower surging levels. The surging is controlled within an allowable range by providing feedback that the EGR amount is increased again when the surging level becomes low. In addition, C1°Ctr, K? , Kg are arbitrary fitting values. Further, control of the EGR valve is not limited to duty control, and the present invention can be applied to EGR control using a step motor or other type of EGR control.

In the fifth embodiment, water temperature is controlled in response to surging. In FIG. 2, 30 is a radiator, whose bottom tank is connected to the engine main body by a cooling water pipe 31.
is connected to the water jacket 32 of. On the other hand, the upper tank of the radiator 30 is connected to a pipe 33 and a water pump (not shown), and as is well known, the water pump introduces cooling water from the water jacket 32 into the radiator 30. A cooling water temperature control valve 34 is provided on the pipe 33, and the temperature control valve 34 controls the amount of water depending on the temperature.

A water temperature sensor 35 is provided in the water jacket, and a water temperature signal is applied to the A/D converter 10a. A drive signal is output from the I10 circuit 10c to the temperature control valve 34.

FIG. 23 is a flowchart showing a driving routine for the temperature control valve 34. In step 2401, the water temperature target value T
EMP is input. 24 when the surging level is high
From 02 to 2403, the flow water temperature target value TEMP is increased by 1, and when the surging level is small, the flow from 2402 to 2403 is increased to 2404 by 1.
It is made smaller by ゜. At 2402', the average value of the target values (C9+CI.)/2 is entered into ΔLN. In step 2405, the actual measured value TH of the water temperature from the water temperature sensor 35 is
W and target value Tt! A size judgment is made with MP, and THW>
When TEMP, the process proceeds to 2406, and the control valve 34 is driven in the direction of increasing the opening degree, while when THW<TEMP, the process proceeds to 2406, and the control valve 34 is controlled in the direction of closing.

In the embodiment described above, when the surging level becomes large, the water temperature target value is increased to suppress the surging by reducing the flow rate to the water jacket 32, and when the surging level becomes small, the water temperature target value is lowered. This increases the flow rate to the water jacket 32. Such control allows the surging level to be kept within a predetermined range.

〔Effect of the invention〕

According to the present invention, by detecting surging, surging can be controlled within a permissible level by feedback changing factors related to engine combustion conditions, and drivability and fuel efficiency can be harmonized.

Furthermore, by using the integrated value of the lean sensor signal as the surging detection means, it is more advantageous in terms of cost than the conventional G sensor.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of the present invention. FIG. 2 is a configuration diagram of an embodiment of the present invention. FIG. 3 is an air-fuel ratio-current characteristic diagram in a lean sensor. FIG. 4 is a diagram showing the lean sensor output by the magnitude of surging. 5 to 9 are flowcharts for explaining the operation of the first embodiment. FIG. 10 is a timing chart of injection pulses. FIG. 11 is a diagram showing the relationship between injection timing and surging level. FIG. 12 is an operation timing diagram of the first embodiment. FIG. 13 is a diagram showing another setting example of the change range of retard angle control. FIG. 14 is a flowchart of a modification of fuel injection timing control. 15 and 16 are diagrams for explaining the setting of the retard angle change range in the control shown in FIG. 14. FIG. 17 is a flowchart of an injection amount calculation routine when controlling the injection amount according to surging. FIG. 18 is a flowchart of an ignition control routine when controlling ignition timing in response to surging. FIG. 19 is a timing diagram of the ignition signal. FIG. 20 is a diagram explaining the duty ratio. FIG. 21 is a diagram showing the relationship between duty ratio and EGR valve opening. FIG. 22 is a flowchart of an EGR control routine when EGR control is performed in response to surging. FIG. 23 is a flowchart of a water temperature control routine when engine water temperature is controlled in response to surging. DESCRIPTION OF SYMBOLS 1... Engine body, 2... Intake passage, 4... Intake pressure sensor, 5... Exhaust passage, 6... Lean sensor, 8.9... Crank angle sensor, 10... control circuit, 11... fuel injection valve, 20... spark plug, 21...
・Igniter, 22...EGR passage, 23...EG
R valve, 24...EGR actuator, 30...Radiator, 34...Water temperature control valve, 35...Water temperature sensor.

Claims (1)

[Claims] Means for generating a signal according to fluctuations in the combustion state of the internal combustion engine, steady state determining means for determining the steady state of the engine, means for comparing the signal level from the signal generating means in the steady state of the engine with a predetermined value, and A surging control device for an internal combustion engine comprising means for controlling at least one engine operating condition factor related to engine combustion conditions in a direction to suppress surging when surging is determined by comparison.