JPH06193514A - Control method for internal combustion engine - Google Patents

Abstract

PURPOSE:To detect combustion condition of an air fuel mixture correctly without using any expensive censer by feedback-controlling an exhaust gas return flow amount on the basis of a combustion roughness value detected by using ion current method. CONSTITUTION:An ignition voltage sensor 17 is provided on the way of connecting wire between a distributor 15 and an ignition plug 16, and its detection signal is supplied to an ECU 5 (electron control unit). On the other hand, an exhaust return flow valve 22 is interposed on the way of an exhaust return flow passage 21, and the opening degree thereof is changed linear by the control signal of the ECU 5. In ion current method, a combustion condition is judged by a voltage value since electric resistance between plug gaps is increased or decreased by the degree of ionization in air-fuel mixture. A combustion roughness value is detected so as to calculate a roughness correcting coefficient on the basis of detected voltage of the ignition voltage sensor 17 in the ECU 5. The previous value of a valve opening degree command value is moltiplied by the roughness correcting coefficient so as to calculate a present value, for the exhaust return flow valve 22 and then a valve opening degree is feedback- controlled while aiming at this value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for an internal combustion engine, and more particularly, to detecting a combustion roughness value by an ion current method and matching the combustion roughness value with a target roughness value based on the detected combustion roughness value. The present invention relates to a control method for an internal combustion engine that feedback-controls the exhaust gas recirculation amount.

[0002]

2. Description of the Related Art A torque substitute value is obtained by detecting an internal cylinder pressure of an internal combustion engine, and a control factor of the internal combustion engine is adjusted based on a deviation between an average torque change amount obtained from the torque substitute value and a predetermined reference value. The technique to do so is conventionally known (refer to Japanese Patent Laid-Open No. 26-75743). However, the above-mentioned conventional method has a problem that not only the cost is increased because the internal pressure of the cylinder of the internal combustion engine needs to be detected by the sensor, but also the calculation is complicated and the responsiveness is poor.

[0003]

By the way, the combustion state of the air-fuel mixture in the cylinder of the internal combustion engine is, for example, in the steady operation state, the maximum value Pm of the cylinder pressure as shown in FIG.
It can be expressed by using a ratio ΔPmax / Pmaxave (hereinafter, referred to as “combustion roughness value”) of a change amount ΔPmax of Pmax with respect to an average value Pmaxave of ax. The combustion roughness value ΔPmax / Pmaxave is a parameter indicating the combustion state of the air-fuel mixture, and the larger the value, the worse the combustion state.

Therefore, if the combustion roughness value of the internal combustion engine is detected by using the ion current method, the combustion state of the air-fuel mixture in the internal combustion engine can be relatively simple without using an expensive cylinder pressure sensor. It becomes possible to detect accurately.

The present invention has been made in view of the above circumstances. The feedback control of the exhaust gas recirculation amount based on the combustion roughness value detected by using the ion current method enables the combustion roughness value to be efficiently increased. The purpose is to match the target roughness value.

[0006]

In order to achieve the above object, the present invention detects a combustion roughness value by an ion current method, and based on the detected combustion roughness value, sets the combustion roughness value to a target roughness value. This is a control method for an internal combustion engine in which the exhaust gas recirculation amount is feedback-controlled so as to match, and the feedback gain when the combustion roughness value exceeds the target roughness value and the feedback gain when the combustion roughness value falls below the target roughness value. The first feature is that the setting is made larger than that.

Further, the present invention detects the combustion roughness value by the ion current method, and based on the detected combustion roughness value, feedback control of the exhaust gas recirculation amount so that the combustion roughness value matches the target roughness value. The second feature of the control method is to set the combustion roughness value to a predetermined value equal to or less than the target roughness value when the combustion roughness value exceeds the target roughness value.

Further, the present invention detects the combustion roughness value by the ion current method, and based on the detected combustion roughness value, feedback control of the exhaust gas recirculation amount so that the combustion roughness value matches the target roughness value. The third feature of the control method is that the operating state of the internal combustion engine is controlled by PID feedback so that the combustion roughness value matches the target roughness value.

Further, the present invention detects the combustion roughness value by the ion current method, and based on the detected combustion roughness value, feedback control the exhaust gas recirculation amount so that the combustion roughness value matches the target roughness value. The fourth feature is that the feedback gain is determined according to the deviation of the combustion roughness value from the target roughness value.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall configuration diagram of an internal combustion engine (hereinafter simply referred to as “engine”) equipped with an exhaust gas recirculation mechanism according to a first embodiment of the present invention and a control system therefor. A throttle valve 3 is provided in the middle of the intake pipe 2. A throttle valve opening degree (θTH) sensor 4 is connected to the throttle valve 3 and outputs an electric signal according to the opening degree of the throttle valve 3 to output an electronic control unit for engine control (hereinafter referred to as “ECU”) 5
Supply to.

The fuel injection valve 6 is provided for each cylinder between the engine 1 and the throttle valve 3 and slightly upstream of the intake valve (not shown) in the intake pipe 2, and each fuel injection valve 6 is provided in a fuel pump (not shown). Is also electrically connected to the ECU 5, and the valve opening time of fuel injection is controlled by a signal from the ECU 5.

The spark plug 16 of each cylinder of the engine 1 is electrically connected to the ECU 5 via the distributor 15, and the ECU 5 controls the ignition timing θIG. An ignition voltage sensor 17 (which forms a capacitor of several pF with the connection line) electrostatically coupled to the connection line is provided in the middle of the connection line connecting the distributor 15 and the ignition plug 16. The detection signal is the ECU 5
Is supplied to.

On the other hand, an intake pipe absolute pressure (PBA) sensor 7 is provided immediately downstream of the throttle valve 3, and the absolute pressure signal converted into an electric signal by the absolute pressure sensor 7 is supplied to the ECU 5. . Further, an intake air temperature (TA) sensor 8 is attached downstream thereof, detects the intake air temperature TA, outputs a corresponding electric signal, and supplies it to the ECU 5.

The engine water temperature (TW) sensor 9 mounted on the main body of the engine 1 is composed of a thermistor or the like, detects the engine water temperature (cooling water temperature) TW, outputs a corresponding temperature signal and supplies it to the ECU 5. The engine speed (NE) sensor 10 and the cylinder discrimination (CYL) sensor 11 are mounted around the cam shaft or crank shaft (not shown) of the engine 1. The engine speed sensor 10 outputs a pulse (hereinafter referred to as a "TDC signal pulse") at a predetermined crank angle position every 180 degrees rotation of the crank shaft of the engine 1, and the cylinder discrimination sensor 11 outputs a predetermined crank angle of a specific cylinder. A signal pulse is output at the position, and each of these signal pulses is supplied to the ECU 5.

The three-way catalyst 14 is arranged in the exhaust pipe 13 of the engine 1 and purifies components such as HC, CO and NOx in the exhaust gas. An oxygen concentration sensor 12 as an exhaust gas concentration detector is mounted upstream of the three-way catalyst 14 in the exhaust pipe 13, detects the oxygen concentration in the exhaust gas, and outputs a signal according to the detected value to output the ECU 5 Supply to. The oxygen concentration sensor 12 is a linear type that outputs a signal proportional to the oxygen concentration.

The ECU 5 further includes a battery voltage sensor 31 for detecting the battery voltage VB, driving wheel speed sensors 33, 34 for detecting the rotational speeds WFL, WFR of the left and right driving wheels of the vehicle on which the engine 1 is mounted, and left and right wheels. Driven wheel speed sensor 3 for detecting the rotational speeds WRL and WRR of the driven wheels
5, 36 are connected, and the detection signals of these sensors are supplied to the ECU 5.

Next, the exhaust gas recirculation mechanism 20 will be described.

The exhaust gas recirculation passage 21 of this mechanism 20 has one end 2
1a is on the upstream side of the three-way catalyst 14 of the exhaust pipe 13, and the other end 21b
Communicate with the intake pipe 2 downstream of the throttle valve 3, respectively. An exhaust gas recirculation valve 22 and a volume chamber 21C for controlling the exhaust gas recirculation amount are provided in the middle of the exhaust gas recirculation passage 21. The exhaust gas recirculation valve 22 is an electromagnetic valve having a solenoid 22a. The solenoid 22a is connected to the ECU 5, and the valve opening degree of the solenoid 22a can be linearly changed by a control signal from the ECU 5. The exhaust gas recirculation valve 22 is provided with a lift sensor 23 that detects the valve opening degree, and the detection signal is supplied to the ECU 5.

The ECU 5 determines the engine operating state based on the engine parameter signals from the above-mentioned various sensors, and the valve opening degree of the exhaust gas recirculation valve 22 set according to the intake pipe absolute pressure PBA and the engine speed NE. Command value LCMD
And exhaust gas recirculation valve 22 detected by the lift sensor 23
The control signal is supplied to the solenoid 22a so as to make the deviation from the actual valve opening value LACT of 0.

The ECU 5 shapes input signal waveforms from various sensors, corrects the voltage level to a predetermined level, converts an analog signal value into a digital signal value, and the like, a central processing circuit (hereinafter referred to as a central processing unit). "CPU") 5b, various calculation programs executed by the CPU 5b, storage means 5c for storing the calculation results, an output circuit 5d for supplying a drive signal to the fuel injection valve 6, and the like.

The CPU 5b calculates the fuel injection time of the fuel injection valve 6, the ignition timing of the spark plug 16 and the valve opening command value of the exhaust gas recirculation valve 22 based on the above various engine parameter signals.

The CPU 5b further controls the valve opening degree of the exhaust gas recirculation valve 22 of the exhaust gas recirculation mechanism 20 according to the engine operating state, and the drive wheel speeds WFL, WFR and the driven wheel speeds WRL, WRL.
Traction control based on WRR is performed. This traction control reduces the output torque of the engine by making the air-fuel ratio lean and cutting off the fuel supply (fuel cut) when an excessive slip state of the drive wheels is detected.

The CPU 5b outputs a signal for driving the fuel injection valve 6, the spark plug 16 and the exhaust gas recirculation valve 22 through the output circuit 5d based on the result calculated as described above.

FIG. 2 is a diagram showing a configuration of a portion related to the detection of the combustion roughness value in the control device of FIG. 1, and the power supply terminal T1 to which the power supply voltage VB is supplied has a primary coil 47 and a secondary coil 48. Ignition coil (ignition means) 4 including
9 is connected. The primary side coil 47 and the secondary side coil 48 are connected to each other at one end thereof, and the primary side coil 47
Is connected to the collector of the transistor 46, and the base of the transistor 46 is connected to the CPU 5 via the drive circuit 51.
b, and its emitter is grounded. An ignition command signal A is supplied from the CPU 5b to the base of the transistor 46. The other end of the secondary coil 48 is connected to the center electrode 16 a of the spark plug 16 via the distributor 15. The ground electrode 16b of the spark plug 16 is grounded.

The ignition voltage sensor 17 is connected to the non-inverting input of the peak hold circuit 42 and the comparator 44 via the input circuit 41. The output of the peak hold circuit 42 is connected to the inverting input of the comparator 44 via the comparison level setting circuit 43. In addition, the peak hold circuit 42
The CPU 5b is connected to the reset input of
A reset signal for resetting the peak hold value is supplied from the PU 5b at an appropriate timing. The output of the comparator 44 is input to the CPU 5b. In addition, the secondary coil 4
A diode 50 is interposed between the distributor 8 and the distributor 15.

FIG. 3 is a circuit diagram showing a specific configuration of the input circuit 41, the peak hold circuit 42, and the comparison level setting circuit 43. In FIG. 3, the input terminal T2 has a resistor 4
Operational amplifier (hereinafter referred to as "op amp") via 15
It is connected to the non-inverting input of 416. Input terminal T
2 is a capacitor 411, a resistor 412 and a diode 41.
4 is connected to ground via a circuit in which 4 is connected in parallel, and the power supply line VBS is connected via a diode 413.
It is connected to the. The capacitor 411 is, for example, 10 ⁴
The voltage detected by the ignition voltage sensor 17 is used to divide the voltage detected by the ignition voltage sensor 17 into several thousandths. As the resistor 412, for example, a resistor having a resistance of about 500 KΩ is used. The diodes 413 and 414 are the operational amplifier 4
It is provided so that 16 input voltages fall within the range of approximately 0 to VBS. The inverting input of the operational amplifier 416 is connected to its output, and the operational amplifier 416 operates as a buffer amplifier (impedance conversion circuit).

The output of the operational amplifier 416 of the input circuit 41 is connected to the non-inverting input of the comparator 44 and the non-inverting input of the operational amplifier 421. The output of the operational amplifier 421 is connected to the non-inverting input of the operational amplifier 427 via the diode 422, and the inverting inputs of the operational amplifiers 421 and 427 are both connected to the output of the operational amplifier 427.
Therefore, these operational amplifiers also operate as buffer amplifiers.

The non-inverting input of the operational amplifier 427 is a resistor 42.
3 and the capacitor 426 to be grounded, and the resistor 423
The connection point between the capacitor 426 and the capacitor 426 is connected to the collector of the transistor 425 via the resistor 424. The emitter of the transistor 425 is grounded, and a reset signal that is high level at reset is input to the base from the CPU 5b.

The output of the operational amplifier 427 is grounded through the resistors 431 and 432 which form the comparison level setting circuit 43, and the connection point of the resistors 431 and 432 is connected to the inverting input of the comparator 44.

According to the circuit of FIG. 3, the peak value of the detected ignition voltage V (output of the operational amplifier 416) is held by the peak hold circuit 42, and the peak hold value is set to 1 by the comparison level setting circuit 43. It is multiplied by a small predetermined number and supplied to the comparator 44 as the comparison level VCOMP. Therefore, at the terminal T4, a pulse signal (comparison determination pulse) that becomes high level when V> VCOMP is established
Is output.

The operation of the circuits 41 to 44 configured as described above will be described with reference to FIG. In (b) and (c) of the figure, the solid line shows the characteristics of the fuel mixture at the time of normal combustion, and the broken line shows the case of misfire (hereinafter referred to as "FI misfire") related to the cause of the fuel system with the maximum combustion roughness value. Show the characteristics. FIG. 7A shows the ignition command signal A.

FIG. 3B shows the detected ignition voltage (output voltage of the input circuit 41) V (B, B ') and the comparison level VC.
The transition of OMP (C, C ') is shown. First, the ignition voltage characteristic (characteristic indicated by the solid line) during normal combustion will be described with reference to this figure.

Immediately after the time t0 when the ignition command signal A is generated, the ignition voltage rises to a value at which the insulation of the fuel mixture (between the discharge gaps of the spark plugs) is destroyed, and after the breakdown, the capacity discharge state before the breakdown is reached. (The discharge state for a very short time by a current of about several hundred amperes) shifts to an inductive discharge state where the discharge voltage is substantially constant (a discharge period of about several milliseconds with a current of about several tens of milliamps). The induced discharge voltage rises as the pressure in the cylinder increases with the compression stroke after time t0. This is because the higher the pressure, the higher the voltage required for induction discharge. At the final stage of the induction discharge, the voltage between the spark plug electrodes becomes lower than the voltage for maintaining the induction discharge due to the reduction of the induction energy of the ignition coil, the induction discharge disappears and the capacity discharge state (the latter capacity discharge State). In the capacitive discharge state, the voltage between the spark plug electrodes rises because the insulation of the fuel mixture is destroyed again, but the residual energy of the ignition coil 49 is small and the voltage rise is small. This is because when the combustion occurs, the electric resistance between the plug gaps is low, and is due to the fact that the fuel mixture at the time of combustion is ionized.

The charge stored in the stray capacitance between the diode 50 and the spark plug 16 (the charge remaining without being discharged between the electrodes) is not discharged to the ignition coil 49 side because of the diode 50. However, since it is neutralized by the ions existing in the vicinity of the electrode of the spark plug 16, the ignition voltage V at the end of the capacity discharge is rapidly reduced.

Next, the ignition voltage characteristics (characteristics indicated by broken lines) when the FI misfire occurs (when combustion does not occur) when the fuel mixture becomes lean or cut due to an abnormality in the fuel supply system or the like will be described. To do. Immediately after the time point t0 when the ignition command signal A is generated, the ignition voltage V rises to a value at which the insulation of the fuel mixture between the spark plug electrodes is destroyed.
The value of the dielectric breakdown voltage at this time is that the ratio of the air occupied by the fuel mixture is larger than in the normal state, the dielectric strength of the fuel mixture becomes large, and since combustion does not occur, the fuel mixture Since the air-fuel mixture is not ionized and the electric resistance between the plug gaps increases, the voltage value becomes higher than that during normal combustion. After that, the state shifts to the induction discharge state as in the normal combustion, but since the discharge resistance is larger than that in the normal combustion, the state shifts to the capacity discharge state faster than in the normal combustion. The value of the capacity discharge (the latter capacity discharge) that occurs at the final stage of the induction discharge is much larger than that during normal combustion because the dielectric breakdown voltage of the fuel mixture is larger than that during normal combustion.

At this time, since there are almost no ions near the electrode of the ignition plug 16, the charge accumulated between the diode 50 and the ignition plug 16 is not neutralized by the ions, and the diode 50 causes the ignition coil 4 to operate.
Since it cannot be back-flowed to 9, it is held as it is, and when the pressure in the cylinder drops and the discharge required voltage becomes equal to the voltage applied by this charge, the spark plug 16 is discharged (FIG. 4 ( b), time t5). Therefore, even after the end of the capacity discharge, the ignition voltage V continues to be in the high voltage state for a relatively long time (compared to the normal combustion).

Curves C and C'in FIG. 4 (b) indicate the ignition voltage V
Comparison level VCOMP obtained from the peak hold value of
, And is reset between times t2 and t3. Therefore, before the time t2, the comparison level VCOMP of the previously ignited cylinder is shown. Also, FIG.
FIG. 4C shows the output of the comparator 44 (hereinafter referred to as “comparison determination pulse”). As is clear from FIGS. 4B and 4C, V> during the time t2 to t4 during combustion> V
COMP becomes, V> VCOMP between times t1 and t5 at the time of misfire, and the output of the comparator 44 becomes high level during that time.

Here, the combustion roughness value RN is an average value Pmaxa of the maximum cylinder pressure values Pmax as shown in FIG.
Ratio ΔPm of change amount ΔPmax of Pmax with respect to ve
Expressed as ax / Pmaxave, the relationship between the exhaust gas recirculation amount (hereinafter referred to as “EGR amount”) EGRM and the combustion roughness value RN is as shown in FIG. 6 (a). Further, the relationship between the EGR amount EGRM and the comparison determination pulse width (time from t2 to t4, or time from t1 to t5) TP is as shown in FIG. In these figures, when EGRM = EGRMH, there is a misfire (complete misfire, the state shown by the broken line in FIG. 4), and EGRM <E
It is shown that good combustion (state shown by the solid line in FIG. 4) is obtained in the range of GRM1. Therefore, EGRM1
Within the range of <EGRM <EGRMH, the comparison determination pulse width TP and the combustion roughness value RN have a relationship as shown in FIG. 7C, and the combustion roughness value RN is determined by measuring the comparison determination pulse width TP. Can be detected.

By detecting the combustion roughness value RN based on the detection voltage of the ignition voltage sensor 17, the following effects are obtained.

Since the ignition voltage sensor 17 can be realized by winding or accommodating a conductor on a high-voltage cord connected to an ignition plug, the ignition voltage sensor 17 has a simple structure and is attached as compared with a combustion pressure sensor or a combustion light sensor. Is easy. Therefore, it can be realized at low cost and can be applied to general passenger cars and motorcycles.

Further, unlike the combustion pressure sensor, the ignition voltage sensor does not need to be attached to the plug seat of the spark plug or the combustion chamber, and the operating conditions are not so severe that it is far superior in terms of durability and reliability. A combustion roughness value sensor can be realized.

FIG. 7 is a flow chart of a program for measuring the comparison determination pulse width TP. This program is executed by the CPU 5b at regular intervals.

In step S41, it is first determined whether or not the monitor condition is satisfied. Here, the monitor condition is
This is a condition that is satisfied when the engine is in the operating state in which the misfire determination should be executed, and is determined by the program of FIG. 8 described later. This condition is not established (step S4
When the answer to 1 is negative (NO), this program is immediately terminated.

When the answer to step S41 is affirmative (Yes), that is, when the monitor condition is satisfied, the IG flag (F
It is determined whether or not (lagIG) is "1" (step S42). This IG flag is "1" when the ignition command signal A is generated in the program for calculating the ignition timing.
Is a flag set to. When the answer to step S42 is negative (No), that is, when the IG flag is "0", the measured value tR of the reset timer is set to 0 (step S43).
This program ends. When the answer to step S42 is affirmative (Yes), that is, when the IG flag is "1", it is determined whether the measured value tR of the reset timer is smaller than the predetermined time tRESET (step S44). Immediately after the IG flag changes from "0" to "1", this answer is affirmative (Y
es), and it is determined whether or not there is a comparison determination pulse, that is, an output pulse of the comparator 44 (step S47). If this answer is negative (No), the program is immediately terminated, and if affirmative (Yes), the count value C of the counter
The value P is incremented by 1 (step S48), and this program ends.

If the answer to step S44 is negative (No),
That is, when tR> tRESET, the count value CP value of the counter and the IG flag are reset to 0 (steps S45 and S46), and this program is ended.

According to this program, the count value CP proportional to the comparison determination pulse width TP can be obtained.

FIG. 8 is a flow chart of a program for judging the monitor condition.

In steps S21 to S25, it is determined whether the detected engine operating parameter value is within a predetermined range. That is, the engine speed NE has a lower limit value NEL (eg, 500 rpm) and an upper limit value NEH (eg, 6,500 rpm).
rpm) (step S21), the absolute value PBA of the intake pipe absolute pressure PBA is the lower limit value PBAL (for example, 260 mmHg).
And the upper limit value PBAH (for example, 760 mmHg) (step S22). The engine water temperature TW is the lower limit value TW
L (eg 40 ° C.) and upper limit value TWH (eg 110 ° C.)
Or not (step S23), the intake air temperature TA is lower than the lower limit value TAL (for example, 0 ° C.) and the upper limit value TAH (for example, 80).
C)) (step S24) and whether the battery voltage VB is higher than the lower limit value VBL (for example, 10 V) (step S25), and one of these determination results is negative (No). When, it is determined that the monitor condition is not satisfied (step S32). If the engine is in the normal operating state, the engine speed NE, the absolute pressure P in the intake pipe
The BA, the engine water temperature TW, and the intake air temperature TA are within the range of the upper and lower limits, and when the battery voltage VB is low, the ignition voltage is lowered and the accurate determination cannot be performed.

All the answers in steps S21 to S25 are affirmative (Y
es), whether or not the open-loop air-fuel ratio lean control not based on the detection value of the oxygen concentration sensor is being executed (for example, such control is executed when the engine is decelerated) (step S26) and the traction control. It is determined whether or not it is being executed (step S27). As a result of these determinations, if either answer is affirmative (Yes), it is determined that the monitor condition is not satisfied (step S32).
This is because the combustion is unstable during the execution of these controls, and it is difficult to control the combustion roughness value described later.

When both the answers in steps S26 and S27 are negative (No), it is further determined whether or not the fuel cut is in progress (step S28). When the answer is affirmative (Yes), that is, in the fuel cut, the timer TMAFC is executed. Is set to a predetermined time (for example, 1 second) to start (step S29), and it is determined that the monitor condition is not satisfied (step S32). When the answer to step S28 is negative (No), that is, when the fuel cut is not in progress, the timer TMAFC is set.
It is determined whether or not the count value of is 0 (step S3).
0). If this answer is negative (No), that is, before the lapse of the predetermined time after the fuel cut, it is determined that the monitor condition is not satisfied (step S32), and the answer of step S30 is affirmative (Yes),
That is, it is determined that the monitor condition is satisfied when a predetermined time has elapsed after the fuel cut ends (step S31).

Steps S29 and S30 take into consideration that the combustion becomes unstable immediately after the fuel cut is completed.

According to the program of FIG. 8, when the engine operating parameter value (NE, PBA, TW, TA, VB) is not within the predetermined range, when the air-fuel ratio lean control or traction control is being executed, during fuel cut or fuel cut. It is determined that the monitor condition is not satisfied within the predetermined time after the end,
In cases other than the above, it is determined that the monitor condition is satisfied.

Next, the control of the EGR amount by the valve opening degree of the exhaust gas recirculation valve 22 will be described with reference to FIGS. 9 to 12.

First, in step S51, the engine speed NE, the intake pipe absolute pressure PBA and the water temperature TW output by the engine speed sensor 10, the intake pipe absolute pressure sensor 7 and the engine water temperature sensor 9 are read (step S5).
1) Based on the read engine speed NE, the intake pipe absolute pressure PBA, and the water temperature TW, the exhaust gas recirculation valve 22 is opened to determine whether or not it is in the EGR region for exhaust gas recirculation (step S52). If the water temperature TW is equal to or lower than the predetermined value in step S52, or the result of searching the map of FIG. 10 based on the engine speed NE and the intake pipe absolute pressure PBA is not within the predetermined EGR region, that is, step S52
When the answer is negative (No), this program is terminated while the exhaust gas recirculation valve 22 is kept closed. On the other hand, if the answer to step S52 is affirmative (Yes), that is, if the water temperature TW exceeds the predetermined value and the result of searching the map is in the predetermined EGR region, the process proceeds to step S53 and EGR is performed.
Perform quantity control.

If the answer to step S52 is affirmative (Yes), E
When in the GR region, the map of FIG. 11 is searched based on the engine speed NE and the intake pipe absolute pressure PBA,
Basic value LMA of valve opening command value LCMD of exhaust gas recirculation valve 22
P is obtained (step S53). Next, based on the combustion roughness value RN obtained from the comparison determination pulse width TP, it is determined whether or not the valve opening degree of the exhaust gas recirculation valve 22 is in a region for feedback control (step S54). This determination is made based on the map of FIG. 11, and when the engine speed NE and the intake pipe absolute pressure PBA are not within the predetermined region on the map, that is, the answer to step S54 is negative (No). Sometimes, the basic value LM of the valve opening command value LCMD of the exhaust gas recirculation valve 22 retrieved from the map of FIG.
AP (that is, the map value LCMDM) is directly used as the valve opening command value LCMD (step S55).

On the other hand, the answer in step S54 is affirmative (Yes
s), that is, engine speed NE and intake pipe absolute pressure PB
If A is in a predetermined area on the map, step S
Move to 56. In the first loop, the answer to step S56 is negative (No), the roughness correction coefficient KRN is set to the initial value (1.0 or the learning value), and the valve opening command value LCMD is set to the initial value (the map value or the learning value). Value) (steps S57 and S58).

When the answer to step S56 is affirmative (Yes), that is, in the second and subsequent loops, step S57,
The combustion roughness value RN is read without performing S58 (step S59). Then, the combustion roughness value RN is compared with a predetermined target roughness value RNref (step S60). The answer to step S60 is affirmative (Yes), that is, the detected combustion roughness value RN is the target roughness value RNre.
If it is smaller than f, the previous value of the roughness correction coefficient KRN is multiplied by the constant A to calculate the current value of the roughness correction coefficient KRN (step S61). On the other hand, if the answer to step S60 is negative (No), that is, if the detected combustion roughness value RN is greater than or equal to the target roughness value RNref, the previous value of the roughness correction coefficient KRN is multiplied by the constant B to obtain the current value of the roughness correction coefficient KRN. Is calculated and the present program is terminated (step S62).

Thus, the present value of the valve opening command value LCMD is calculated by multiplying the previous value of the valve opening command value LCMD by the roughness correction coefficient KRN calculated in step S61 or step S62. Opening command value LCM
The valve opening degree of the exhaust gas recirculation valve 22 is feedback-controlled with the current value of D as the target value (step S63).

By the way, the constants A and B are set so as to satisfy A> 1.0 B <1.0 | A-1.0 | <| 1.0-B |. Therefore, step S6
If the answer of 0 is affirmative (Yes) and the combustion roughness value RN is smaller than the target roughness value RNref, the constant A
Roughness correction coefficient K by multiplying (> 1.0)
RN increases. As a result, the valve opening command value LCMD can be increased to control the EGR amount in the increasing direction, and the combustion roughness value RN can be made to match the target roughness value RNref. On the contrary, if the answer to step S60 is negative (No) and the combustion roughness value RN is not less than the target roughness value RNref, the roughness correction coefficient KRN is decreased by multiplying by the constant B (<1.0). As a result, the valve opening command value LCMD is decreased to control the EGR amount in the decreasing direction,
The combustion roughness value RN can be matched with the target roughness value RNref.

At this time, | A-1.0 | <| 1.0-B
From the relationship of |, the decrease amount of the roughness correction coefficient KRN by the constant B becomes larger than the increase amount of the roughness correction coefficient KRN by the constant A. This means that the combustion roughness value RN
Becomes equal to or higher than the target roughness value RNref, the combustion roughness value RN rapidly decreases, and the combustion roughness value RN
Is lower than the target roughness value RNref, it means that the combustion roughness value RN slowly increases. That is, the combustion roughness value RN is equal to the target roughness value RNr.
If the value exceeds ef, the combustion state becomes poor.
As a result, the poor combustion state is quickly eliminated, so that the fuel consumption rate can be reduced and the exhaust gas emission characteristics can be improved without deteriorating the drivability. Further, the combustion roughness value RN is the target roughness value RN.
Although the combustion state is maintained good even if it becomes less than or equal to ref, it is necessary to increase the combustion roughness value RN to the target roughness value RNref from the viewpoint of exhaust gas emission characteristics. In this case, the combustion roughness value RN can be slowly increased by the constant A, and the combustion roughness value RN can be matched with the target roughness value RNref without overshooting in a region where the combustion state becomes poor.

FIG. 12 shows the valve opening command value L under the above control.
This is a schematic representation of an example of CMD fluctuation, in which the amount of change in the valve opening command value LCMD in the decreasing direction is large and the amount of change in the increasing direction is small across the target roughness value RNref. Is understood.

Next, a second embodiment of the present invention will be described with reference to FIGS.

In the flow chart of FIG. 13, only step S64 is the flow chart of FIG. 9 (first embodiment).
Is different from That is, in the second embodiment, step S60
Then, the target roughness value RNref and the combustion roughness value RN are compared, and the combustion roughness value RN is compared with the target roughness value RNre.
If smaller than f, the constant A (A> A) as in the first embodiment.
Roughness correction coefficient KRN
However, the combustion roughness value RN is equal to the target roughness value R
If Nref or more, the basic value LMAP of the valve opening command value LCMD retrieved in step S53 (map value LCMD
The program is terminated with M) as it is as the valve opening command value LCMD (step S64).

As a result, as shown in FIG. 14, when the combustion roughness value RN exceeds the target roughness value RNref, the valve opening command value LCMD decreases to the basic value LMAP all at once.
As a result, the combustion roughness value RN becomes the target roughness value RNr.
It is possible to avoid deterioration of the combustion state beyond ef as much as possible.

Next, a third embodiment of the present invention will be described with reference to FIGS.

The flowchart of FIG. 15 differs from the flowchart of FIG. 9 (first embodiment) only in steps S65 to S68. That is, in the third embodiment, when the combustion roughness value RN is read in step S59, the combustion roughness value RN is calculated from the target roughness value RNref.
The deviation ΔKRN is calculated by subtracting (step S65). Next, the current value of the deviation ΔKRN is set to PI.
The current value of the proportional correction term KRNP is multiplied by the proportional constant KP of the D feedback control, the current value of the deviation ΔKRN is multiplied by the integration constant KI, and the integral correction term KRN is multiplied.
The current value of the integral correction term KRNI is calculated by adding the previous value of I, and the current value of the differential correction term KRND is calculated by multiplying the difference between the current value of the deviation ΔKRN and the previous value by the differential constant KD. Above constants KP, KI, KD
Is stored in advance in the storage means 5c as a table value or a map value.

Next, the proportional correction term KRNP, the integral correction term KRNI and the differential correction term KRND are added to calculate a roughness correction coefficient KRN (step S67), and the valve opening command value is calculated using this roughness correction coefficient KRN. The LCMD is filtered, and the result is set as the final valve opening command value LCMD, and the program ends (step S6).
8).

According to the third embodiment, when the combustion roughness value RN is subjected to PID feedback control, its deviation Δ
Since the magnitudes of the proportional correction term KRNP, the integral correction term KRNI, and the derivative correction term KRND are determined based on the magnitude of KRN, the combustion roughness value RN is the target roughness value RNr.
Each of the correction terms KRNP, KRN becomes closer to ef.
The values of I and KRND decrease. As a result, as shown in FIG. 16, the target roughness value RNref is promptly increased without overshooting or vibrating the combustion roughness value RN.
Can be matched to.

Next, a fourth embodiment of the present invention will be described with reference to FIGS.

The flowchart of FIG. 17 is different from the flowchart of FIG. 15 (third embodiment) only in steps S69 and S70. That is, in the fourth embodiment, when the deviation ΔKRN is calculated in step S65, the product of the current value of the deviation ΔKRN and the integral constant KI is added to the previous value of the integral correction term KRNI to obtain the integral correction term KR.
The current value of NI is calculated (step S69). And
The current value of the integral correction term KRNI calculated in step S69 is set as the roughness correction coefficient KRN (step S70), and the valve opening command value LCM is calculated using this roughness correction coefficient KRN.
This D is filtered, and the result is set as the final valve opening command value LCMD, and this program ends (step S68).

The fourth embodiment corresponds to the PID feedback control of the third embodiment in which only the integral correction term KRNI is adopted. Therefore, as shown in FIG. 18, although the accuracy is less than that of the third embodiment (see FIG. 16) in which the PID feedback control is adopted, it is possible to obtain the accuracy which is practically problem-free while simplifying the control system.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various design changes can be made.

[0074]

As described above, according to the first feature of the present invention, the combustion roughness value is detected by the ion current method, and the exhaust gas recirculation amount is feedback-controlled so that the combustion roughness value matches the target roughness value. When the combustion roughness value exceeds the target roughness value, the feedback gain when the combustion roughness value exceeds the target roughness value is set to be larger than the feedback gain when the combustion roughness value falls below the target roughness value. It is possible to promptly get out of the state where the combustion state deteriorates, and to reduce the fuel consumption rate and improve the exhaust gas emission characteristics without deteriorating the drivability.

Further, according to the second feature of the present invention, when the combustion roughness value is detected by the ion current method and the exhaust gas recirculation amount is feedback-controlled so as to match the combustion roughness value with the target roughness value, the combustion is performed. When the roughness value exceeds the target roughness value, by setting the combustion roughness value to a predetermined value equal to or less than the target roughness value, the combustion roughness value exceeds the target roughness value and the state in which the combustion state deteriorates is quickly removed. However, the fuel consumption rate can be reduced and the exhaust gas emission characteristics can be improved without deteriorating the drivability.

Further, according to the third feature of the present invention, when the combustion roughness value is detected by the ion current method and the exhaust gas recirculation amount is feedback-controlled so as to match the combustion roughness value with the target roughness value, the internal combustion engine is used. By performing PID feedback control on the operating state of the engine, it is possible to accurately match the combustion roughness value with the target roughness value, and to reduce the fuel consumption rate and improve the exhaust gas emission characteristics without deteriorating the drivability.

Further, according to the fourth feature of the present invention, when the combustion roughness value is detected by the ion current method and the exhaust gas recirculation amount is feedback controlled to match the combustion roughness value with the target roughness value, By determining the feedback gain according to the deviation of the combustion roughness value from the roughness value, the combustion roughness value can be quickly matched to the target roughness value without overshooting or oscillating, and the fuel consumption rate can be improved without deteriorating the drivability. Reduction and improvement of emission characteristics of exhaust gas can be achieved.

[Brief description of drawings]

FIG. 1 is a block diagram of an internal combustion engine and its control device.

FIG. 2 is a diagram showing a circuit configuration for detecting a combustion roughness value.

FIG. 3 is a circuit diagram showing a specific configuration of the circuit of FIG.

FIG. 4 is a time chart showing changes in ignition voltage.

FIG. 5 is a time chart showing changes in cylinder pressure.

FIG. 6 is a diagram illustrating a relationship between an exhaust gas recirculation amount, a combustion roughness value, and a comparison determination pulse width.

FIG. 7 is a flowchart of a program for measuring a comparison determination pulse width.

FIG. 8 is a flowchart of a program for determining monitor conditions.

FIG. 9 is a flowchart of a program for determining the exhaust gas recirculation amount.

FIG. 10 is a graph showing engine speed and intake pipe absolute pressure EG.
Map to search R region

FIG. 11 is a map for searching a basic value of a valve opening command value and a roughness feedback region from the engine speed and the absolute pressure in the intake pipe.

FIG. 12 is a graph showing changes in valve opening command value.

FIG. 13 is a flowchart according to the second embodiment and corresponding to FIG. 9.

FIG. 14 is a graph corresponding to FIG. 12 according to the second embodiment.

FIG. 15 is a flowchart according to the third embodiment and corresponding to FIG.

FIG. 16 is a graph corresponding to FIG. 12 according to the third embodiment.

FIG. 17 is a flowchart corresponding to FIG. 9 according to the fourth embodiment.

FIG. 18 is a graph corresponding to FIG. 12 according to the fourth embodiment.

[Explanation of symbols]

 1 engine (internal combustion engine) 6 fuel injection valve 16 spark plug 22 exhaust gas recirculation valve RN combustion roughness value RNref target roughness value ΔKRN deviation

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaki Kanehiro 1-4-1 Chuo, Wako-shi, Saitama Prefecture Honda R & D Co., Ltd. (72) Inventor Yuichi Shimazaki 1-4-1 Wako, Saitama Prefecture No. Stock Company Honda Technical Research Institute

Claims (4)

[Claims] 1. A combustion roughness value (R
N) is detected, and based on the detected combustion roughness value (RN), the combustion roughness value (RN) is changed to the target roughness value (R).
Nref) is a control method for an internal combustion engine in which the exhaust gas recirculation amount is feedback-controlled so that the combustion roughness value (RN) is equal to the target roughness value (RNre).
A method for controlling an internal combustion engine, characterized in that the feedback gain when it exceeds f) is set to be larger than the feedback gain when the combustion roughness value (RN) falls below the target roughness value (RNref). 2. A combustion roughness value (R
N) is detected, and based on the detected combustion roughness value (RN), the combustion roughness value (RN) is changed to the target roughness value (R).
Nref) is a control method for an internal combustion engine in which the exhaust gas recirculation amount is feedback-controlled so that the combustion roughness value (RN) is equal to the target roughness value (RNre).
A control method for an internal combustion engine, comprising setting the combustion roughness value (RN) to a predetermined value equal to or less than a target roughness value (RNref) when the value exceeds f). 3. A combustion roughness value (R
N) is detected, and based on the detected combustion roughness value (RN), the combustion roughness value (RN) is changed to the target roughness value (R).
A method for controlling an internal combustion engine in which the exhaust gas recirculation amount is feedback-controlled so as to match Nref), in which a combustion roughness value (RN) is changed to a target roughness value (RNre).
In order to match f), the operating state of the internal combustion engine (1) is set to P
A method for controlling an internal combustion engine, characterized by performing ID feedback control. 4. A combustion roughness value (R
N) is detected, and based on the detected combustion roughness value (RN), the combustion roughness value (RN) is changed to the target roughness value (R).
A method of controlling an internal combustion engine in which the exhaust gas recirculation amount is feedback-controlled to match Nref), and a feedback gain is determined according to a deviation (ΔKRN) of a combustion roughness value (RN) from a target roughness value (RNref). A method for controlling an internal combustion engine, comprising: