JPS59136544A - Control apparatus for intenal-combustion engine - Google Patents

Abstract

PURPOSE:To enable to control performance of an engine without influence of aging or the like, by detecting deviation of the maximum value of combustion pressure detected from the internal pressure of a combustion chamber, the crank angle at which the combustion pressure becomes maximum and the values of rising and falling gradients of the combustion pressure from respective reference values, and executing learning- control to eliminate the deviation. CONSTITUTION:The maximum value of combustion pressure, the crank angle at which the combustion pressure becomes maximum, the rising and falling gradients of the combustion pressure, the quantity of produced heat and the period when combustion is continued are calculated by applying various signals S1-S7 representing the operational conditions of an engine, inclusive of a signal indicating the internal pressure of a combustion chamber, to a parameter calculating means 21. Then, deviation of the air-fuel ratio, the injection timing and the rate of exhaust-gas recirculation from respective aimed values under a prescribed operational condition of the engine is detected by comparing at least one or two or more combinations of the above parameters with reference value stored in a memory 23 by a learning means 22, and each of the aimed control values stored in a memory 24 are rewritten to eliminate the deviation. Thus, the air-fuel ratio, the ignition timing and the rate of exhaust-gas recirculation are controlled at least via an output means 25 according to the results of learning.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application of the Invention) The present invention relates to a device for optimally controlling the combustion state of an internal combustion engine.

(Prior Art) As a technique for controlling the combustion state of an internal combustion engine, the following, for example, has been disclosed.

First, Japanese Patent Publication No. 49-17973 converts the pressure in the combustion chamber into an ionization current, detects the peak value of this ionization current, adjusts the ignition timing, and optimally controls the angle of the highest combustion pressure point with respect to top dead center. This aims to maximize the output of the internal combustion engine.

In addition, Japanese Patent Publication No. 49-29209 discloses a device that electrically detects the peak value generation timing of the combustion chamber pressure of an internal combustion engine and a device that electrically detects the rotational angle reference position of the crankshaft. The position where the peak value occurs is detected using the crankshaft rotational angle reference position signal, and the ignition position is changed to make this the optimum position.

Furthermore, Japanese Patent Application Laid-Open No. 53-56429 attempts to reduce harmful components in exhaust gas by controlling the ignition timing so that the pressure within the combustion chamber does not exceed a predetermined value.

Furthermore, JP-A-52-77935 discloses an ignition timing control method that determines the difference between the maximum pressure of combustion gas and a predetermined reference setting pressure and controls the maximum pressure to match the reference setting pressure. Also disclosed is Japanese Patent Application Laid-Open No. 52-15143
In No. 2, as the ignition timing advances, the ratio P m a of the maximum value Pmax of the combustion chamber pressure and the motoring pressure Pm
x/P m tends to become thicker, and M B T
(minimum 5parkadvancc for
best torque) takes advantage of the property that Pmax/Pm is almost constant regardless of parameters such as rotational speed, suction negative pressure, air-fuel ratio, etc.
/ P m is controlled so that it is constant,
Compared to conventional ignition timing control systems that program the average ignition timing based on internal combustion engine test results, this system is superior in that it does not require correction for atmospheric conditions, variations in internal combustion engine characteristics, etc. JP-A-53-60431, like the above-mentioned JP-A-52-151432, has Pmax/j
In an ignition timing control device that controls m so that it becomes a predetermined value, the ignition timing is controlled to be delayed when knocking occurs.

Furthermore, JP-A No. 52-39038 states that it is difficult to program the optimal ignition timing that minimizes the fuel consumption rate using only two parameters: the rotational speed of the internal combustion engine and the intake pressure.
In addition, considering variations in internal combustion engines and ignition systems, torque changes are generated by periodically changing the ignition timing, and the phase relationship between the changing phase of the ignition timing and the torque is determined, and the By controlling the ignition timing, an attempt is made to operate the internal combustion engine at the minimum fuel efficiency.

However, in the above-mentioned conventional technology, the motoring pressure (the pressure generated when the gas in the combustion chamber is compressed by the up and down movement of the piston) and the combustion pressure (
pressure caused by the combustion of the air-fuel mixture). Therefore, when the value of the pressure waveform changes, it is not possible to clearly distinguish whether the indicated value of the pressure sensor has changed or the phenomenon itself has changed.

In addition, since it was not possible to calibrate the output of the pressure sensor that detects the pressure in the combustion chamber while the internal combustion engine was operating, it was not possible to calibrate the output of the pressure sensor that detects the pressure in the combustion chamber. Cannot be clearly identified.

Therefore, in conventional devices, the maximum value of combustion pressure, which is closely related to combustion, the crank angle at which combustion pressure is maximum,
Since it was not possible to accurately detect parameters such as the rising and falling slopes of combustion pressure, heat release amount, and combustion duration in real time, it was possible to effectively detect variations between solids in internal combustion engines and changes over time. Since the ignition timing, air-fuel ratio, and EGR amount were individually controlled, there was a problem in that sufficient performance could not be obtained in combustion control.

(Object of the Invention) The present invention has been made to solve the above problem, and detects the parameters closely related to combustion during actual operation of the internal combustion engine, and adjusts the internal combustion engine according to the values. The object of the present invention is to provide a device that optimally controls combustion by performing learning control so as to eliminate deviations from the design target value due to individual differences and changes over time.

(Summary of the invention) In order to achieve the above object, the present invention measures the pressure in the combustion chamber of an internal combustion engine, and uses the measured value to determine the maximum combustion pressure, the crank angle at which the combustion pressure is maximum, and the rising slope of the combustion pressure. , a falling slope, a heat release amount, and a combustion duration time, and comparing at least one or a combination of two or more of the above parameters with a base/$ value. By this, deviations from the design target values of the air-fuel ratio, ignition timing, and EGRi caused by variations between individual internal combustion engines and changes over time are detected, and the air-fuel ratio and ignition timing are adjusted to eliminate the differences between the above parameters and the reference values. Control that rewrites the control target values (reference values for controlling air-fuel ratio, etc.) of timing and EGR amount, that is, learning control, is performed, and the air-fuel ratio, ignition timing, and EGR are changed according to the learned results.
It is configured to control at least one of the R amounts.

(Embodiments of the Invention) The present invention will be explained in detail below based on embodiments. Fig. 1 is a diagram showing an embodiment of an internal combustion engine control device according to the present invention.

In FIG. 1, l is the internal combustion engine body (in the case of a four-cylinder engine), 2 is an intake pipe, and 3 is an exhaust pipe.

The upstream and downstream parts of the throttle valve 4 of the intake pipe 2 are connected by a bypass pipe 6, and an air amount regulator 7 is provided in the middle of the bypass pipe 6. This air amount regulator 7 is configured, for example, by a solenoid valve or a combination of a solenoid valve and a negative pressure valve, and is configured by a bypass pipe 6 in response to a flow rate control signal S8.
Adjust the intake air flow rate.

Further, an intake air amount sensor (for example, an air flow meter) 8 outputs an intake air amount signal SL corresponding to the amount of air taken into the internal combustion engine.

In addition, the throttle sensor 5 that is linked to the throttle valve 4 is
A throttle signal S2 corresponding to the opening degree of the throttle valve 4 is output.

Further, a fuel injection valve 9 is provided in the intake port of each cylinder, and injects fuel in an amount corresponding to the injection signal S9.

On the other hand, the exhaust pipe 3 is provided with an exhaust sensor 10.

This exhaust sensor 10 operates according to the oxygen concentration in the exhaust gas, and when the air-fuel mixture is rich (the air-fuel ratio is smaller than the stoichiometric air-fuel ratio), the level is high, and when the air-fuel mixture is lean (the air-fuel ratio is larger than the stoichiometric air-fuel ratio), the level is high. In this case, a low level air-fuel ratio signal S7 is output.

Further, the exhaust pipe 3 and the intake pipe 2 are connected via an exhaust gas recirculation pipe 11.

A recirculation amount regulator 12 is provided in the middle of the exhaust gas recirculation pipe 11, and controls the amount of exhaust gas recirculation in accordance with the recirculation amount control signal S10. The structure of this reflux amount regulator 12 is similar to that of the air amount regulator 7 described above.

The ignition device 13, which is controlled by the ignition signal Sll, performs ignition by applying a high voltage to a spark plug (not shown) provided for each cylinder. is a unit angle (for example, 1
0) Outputs unit angle signal S4 every time it rotates, and calculates the reference angle (
In a 4-cylinder engine, the reference angle signal S5 is generated every 180') rotation.
Output.

Further, the water temperature sensor 15 outputs a temperature signal S3 corresponding to the temperature of the cooling water of the internal combustion engine.

Moreover, the pressure sensor 16 outputs a pressure signal S6 corresponding to the combustion chamber pressure. As a pressure element, a piezoelectric element 20 in the form of a washer can be used, for example, as shown in FIG. 2, between the spark plug 18 and the combustion chamber wall 19.

Further, the arithmetic unit @17 is, for example, a CPU and a RAM.

It is composed of a microcomputer consisting of ROM, Ilo, A/D converter, etc., inputs signals S1 to S7 from each sensor listed in -1-, performs various calculations, and outputs each control signal of the two pairs. 38~Output Sll.

Next, a method of calibrating the output of the pressure sensor, which is the basis of the control of the present invention, will be explained.

Note that this calibration calculation is performed by the calculation device 17 according to various input signals Sl to S7.

Pressure sensors installed in automobile internal combustion engines operate in environments ranging from extremely cold temperatures of around -40°C to high temperatures of over 100°C. Pressure sensors naturally operate normally within this temperature range. There is a need to.

However, pressure sensors consisting of piezoelectric elements and strain gauges
Temperature changes at high temperatures are large, and it is extremely difficult to accurately compensate for this.

Furthermore, in a device that is used for many years, such as a car, it is naturally expected that changes will occur over time, but this will be corrected accurately for the car. This was extremely difficult.

However, there is a proportional relationship between combustion chamber pressure and intake air amount.
Furthermore, since the temperature change range of the intake air is much narrower than that of the pressure sensor, the output of the pressure sensor can be calibrated based on the amount of intake air.

FIG. 3 is a diagram showing the relationship between the intake air amount (determined from the intake air amount signal SL force 1) and the output of the pressure sensor 16.

In FIG. 3, Ll is the combustion chamber pressure (pressure sensor 16
B2 indicates the motor 1' pressure (the pressure generated when the gas in the combustion chamber is compressed by the up and down movement of the piston), and the difference between Ll and B2 is the combustion pressure (the pressure generated by the combustion of the air-fuel mixture). It is.

Note that the value of the combustion chamber pressure changes depending on the position of the piston, that is, the crank angle, ignition timing, EGR amount, and air-fuel ratio. Operating status (indicates the value to be monitored).

As can be seen from FIG. 3, there is a proportional relationship between the amount of intake air and the pressure in the combustion chamber at a constant crank angle and under certain operating conditions. It is possible to calibrate the combustion chamber pressure using nitrogen.

Further, as will be described later, if the motoring pressure (±) can be separated from the operating combustion chamber pressure, the above calibration can be performed reliably and easily.

Note that the upper limit of the temperature of the intake air is approximately 50° C., and its temperature change range is much narrower than the temperature change range of the pressure sensor, making temperature correction of the intake air amount easy.

Next, FIG. 4 is an embodiment of a flowchart showing the calculation of the present invention.

In FIG. 4, first, with the ignition timing, EGR amount, and air-fuel ratio constant at Pl, the combustion chamber pressure at a specific crank angle is measured and stored.

As will be described later, when using the motoring pressure determined from the combustion chamber pressure, it is not necessary to keep it constant at t±, such as one ignition timing, and it is sufficient if it is a value at a specific crank angle.

Next, in B2, the amount of intake air is measured and stored.

Note that this is not limited to the amount of intake air, but also the equivalent operating variables.
For example, suction negative pressure, throttle valve opening, etc. may be used.

Next, at B3, the intake air temperature is measured (measured by a temperature sensor, such as a thermistor, etc. provided in the intake pipe 2), and the intake air amount determined at B2 is thereby corrected to the reference temperature value.

Next, in B4, using the proportional relationship shown in Figure 3 above, the reference value previously determined by experiment for that type of internal combustion engine, Pl, and the combustion chamber pressure and intake air amount determined in B3 are calculated. Compare with the corresponding relationship.

If the value of the combustion chamber pressure is biased toward the excessive side at B4, the process goes to B5 and a correction is made to reduce the value of the pressure sensor by the deviation from the reference value.

If the value of the pressure inside the combustion chamber is biased toward the small side at B4, the process goes to B6, and a correction is made to increase the value of the pressure sensor by the deviation from the reference value.

By the calculations described above, the output of the pressure sensor can be automatically calibrated during operation of the internal combustion engine.

In calculation 1, a method of calibrating using the combustion chamber pressure itself was shown, but in the flowchart of FIG. 4, motoring pressure may be used instead of the combustion chamber pressure.

Next, a method for identifying the motoring pressure waveform and the combustion pressure waveform will be explained.

The combustion chamber pressure waveform detected by the pressure sensor 16 attached to the actual internal combustion engine is as shown in FIG.

In FIG. 5, GA-GD shows a change in the pressure waveform in the combustion chamber due to changing the ignition timing, and shows a state in which the ignition timing gradually becomes later from GA to GD. Furthermore, At, Bl, C1, and DI each represent the entire combustion chamber pressure waveform, and A2, B2, C2, and B2 each represent the motoring pressure waveform. The shaded area is the combustion pressure.

As can be seen from FIG. 5, since the combustion chamber pressure waveform is a combination of motoring pressure and combustion pressure, the motoring pressure and combustion pressure cannot be determined separately as is. However, the motoring pressure waveform is
Due to its nature, it is symmetrical with respect to top dead center TDC, so G
By using a waveform such as C or GD, it becomes possible to separate the motoring pressure and the combustion pressure.

In other words, in the GC and GD waveforms, from the rising point of the waveform (corresponding to the bottom dead center) TO to the top dead center TDC, this waveform is memorized because only the motoring pressure is present, and from the top dead center TDC onward, the waveform is stored. If this value is calculated symmetrically with respect to the top dead center TDC, only the motoring pressure excluding the combustion pressure will be obtained, and if this value is subtracted from the entire combustion chamber pressure, the combustion pressure will be obtained.

Below, the waveforms of GB and GC in Fig. 5 and Fig. 6 (7) 7
0-Explain based on the chart.

In Fig. 6, first at P7, set the ignition timing to top dead center TDC.
Set the position sufficiently earlier, for example, T2 in Fig. 5 GB,
The pressure waveform inside the combustion chamber should be monomodal like GB.

Next, with Pa, set α=α+1. This means that the ignition timing is delayed by a certain amount from the previous value.

Next, in P9, the ignition timing is set to T2+α. .

Due to Pa and P9, the ignition timing is delayed by a certain amount every L calculations.

Next, the PIO measures the combustion chamber pressure for each crank angle, and calculates and stores the average value for each crank angle. In this measurement, the value at 1/1 is determined under the same operating condition. Furthermore, the average value of the measured values is calculated because there is variation in the -times of measurement.

Next, for pH, the previous measured value Pb (the one where the crank angle is closer to TO) is compared with the current measured value Pa.

If Pa≧Pb, this indicates that the pressure is increasing (before the maximum value of the pressure waveform), so return to Pa and repeat the above procedure. If Pa<Pb, this indicates that there is at least one local maximum value, so go to T12.

In P L, 2, it is determined whether Pa continues to be smaller, that is, whether it has continuously decreased.

If YES in T12, it indicates that the characteristic is unimodal as shown in GB in FIG. 5, so the process returns to Pa and repeats the above procedure.

If NO at T12, the process goes to PL3, and it is determined whether there is a change from small to large, that is, whether there is a local minimum value.

If No at T13, return to Pa and repeat as above.

If YES in T13, it indicates a bimodal characteristic as shown in the GC waveform in FIG. 5, so go to T14.

At T14, the crank angle where the minimum value occurs is the top dead center TD
It is determined whether it is after C.

T
Go to 178 to determine the number of times such a condition has occurred.

If it is less than a predetermined number of times (for example, 1 to 2 times) at T17,
Since it is considered to be a constant error of +11I, return to Pa.

If this continues for a predetermined number of times or more, it is likely that abnormal combustion has occurred or that an abnormality has occurred in the pressure sensor 16 or the like, so the process goes to T18 and an abnormality alarm is issued.

On the other hand, if YES in P14, since the waveform is the GC waveform of FIG. 5, the combustion pressure and motoring pressure are calculated in T15 and T16.

The above calculation will be explained below using the GC waveform shown in FIG.

In the GC shown in FIG. 5, To is set to O1 and top dead center TDC is set to 0.
If TI is 20, the motoring pressure waveform is at top dead center T.
Since it is symmetrical with respect to DC, it is equidistant from top dead center TDC. Motoring pressure Pm at crank angles T3 and T4
are equal, and the pressure Pm (T4) at T4 is Pm (T4)
=Pmf (2θ-T4). However, Pmf is O~
The function of pressure versus crank angle up to θ is shown.

Therefore, by performing the same calculation as above for each crank angle from top dead center TDC to T1, it is possible to detect the motoring pressure (waveform of C2) at all crank angles.

Then, by subtracting the obtained motoring pressure from the combustion chamber pressure (CI waveform) for each crank angle, it is possible to obtain the combustion pressure Pn.

Note that under the same operating conditions (the same amount of intake air), the motoring pressure waveform is the same, so once the motoring pressure is determined, the ignition timing is advanced to the normal advance value, and the above is calculated from the combustion chamber pressure at that time. The required combustion pressure can be determined by subtracting the motoring pressure.

In FIG. 6, Pm(k) (k is a variable indicating each crank angle) is obtained at IF'15, and Pn(k) is obtained at PI3. Note that F(k) represents the pressure inside the combustion chamber at each crank angle.

Since the motoring pressure separated as described above is proportional to the intake air amount regardless of other operating variables such as ignition timing, it is necessary to specify the operating state by performing the correction calculation shown in Figure 4 based on this value. This eliminates the need for accurate calibration.

Next, a method of measuring the maximum value of combustion pressure, combustion duration, amount of heat generation, etc. will be explained.

FIG. 7 is an example of a combustion chamber pressure waveform, where GF is a combustion pressure waveform, and GG is an integral value of GF. Further, in GE, a broken line E1 and a solid line E2 each indicate a pressure waveform in the combustion chamber when the ignition timing is changed, and E3 is a motoring pressure waveform. Also CF
In and GG, the broken line waveform corresponds to El, and the solid line waveform corresponds to E2.

In FIG. 7, first, from the pressure waveform in the combustion chamber as shown in GE, the motoring pressure E3 is determined by the method described above.
By separating it and subtracting it from El and E2, a combustion pressure waveform as shown in CF is obtained.

Next, use the well-known successive approximation method (a method for finding peaks by sequentially comparing adjacent values) from the GF waveform.
By detecting the position where the differential value becomes zero, the maximum combustion pressure value FLI, PI2 and its generation position T can be determined.
Find DC and T8.

Further, 1 and τ2 are the combustion duration times, which are the times from crank angles T5 and T6 at which the GF waveform became 0 or more to crank angles T7 and T9 at which it returned to 0. To convert the crank angle into time, calculate the time it takes to rotate a unit crank angle (for example, 1') from the rotational speed of the internal combustion engine at that time, and add T5 to T7 to that value.
Alternatively, the crank angle of T6 to T9 may be multiplied by 11]. Further, the waveform of GG is an integral of the waveform of GF, and its maximum value G1. G2 indicates the amount of heat generated.

Therefore, by finding the value of GG at T7 or T9, the amount of heat generated can be obtained for each.

Furthermore, the slope of the rise and fall of the combustion pressure waveform (average slope) can be determined from the GF waveform.

The maximum value of the combustion chamber pressure and the combustion pressure determined from it, its crank angle, rising slope, falling slope, combustion duration, and heat generation amount are different from each other even under the same operating conditions. It changes by changing the fuel ratio, ignition timing, etc., and depending on these values, the amount of NOx emissions, generated torque, fuel efficiency, etc. change significantly. Therefore, by calibrating the output of the pressure sensor using the method described above and accurately knowing the maximum value of combustion pressure, etc., it is possible to accurately control the combustion state without being affected by temperature changes or changes over time. Become.

Next, the relationship between the EGR amount, air-fuel ratio, ignition timing, and combustion chamber pressure will be explained in detail.

FIG. 8 shows changes in the pressure waveform in the combustion chamber when the EGR amount, air-fuel ratio, and ignition timing are changed under a constant operating state.

First, GH is a waveform when the EGR amount is changed, and when the EGR amount is increased from a state where the combustion chamber pressure is initially Hl, the combustion chamber pressure changes as shown by H2. Moreover, H3 is a motoring pressure waveform.

As can be seen from GH, when the EGR amount is increased, the combustion speed becomes slower, and the maximum value of the combustion chamber pressure decreases from HLI to Hl2.

In order to further clarify this change, GH' shows a waveform obtained by separating only the combustion pressure from the waveform of G)I.

In GH', Hll corresponds to Hl of GH, and Hl2
corresponds to H2.

As can be clearly seen from the waveform of GH', as the EGR profile increases, the maximum value of combustion pressure decreases from HPII to HP12, and the crank angle at which the maximum value occurs changes from TDC to TIO.
deviates significantly.

The above characteristics cannot be seen from the pressure waveform in the combustion chamber of GH, and become clear only when only the combustion pressure is separated like GH'.

Next, GJ shows the change in the combustion chamber pressure waveform when the air-fuel ratio is changed, Jl and J2 are the combustion chamber pressure waveform, J3 is the motoring pressure, and GJ' is the combustion pressure waveform.

Under certain operating conditions, the air-fuel ratio is the stoichiometric air-fuel ratio (A/F=
The combustion pressure reaches its maximum near 14.8), and the combustion pressure tends to decrease from this point whether the air-fuel ratio is rich or lean.

Furthermore, even if the air-fuel ratio is changed, the crank angle at which the combustion pressure is maximum will hardly change.

Next, GK and GK'' indicate changes in combustion chamber pressure and combustion pressure when the ignition timing is changed, Kl and 2 are combustion chamber pressure waveforms, and K3 is a motoring pressure waveform.

When the ignition timing is changed, the crank angle at which the combustion chamber pressure reaches its maximum value changes greatly from TDC to Tll. Further, even if the maximum value of the combustion pressure is the same value KLII, the maximum value of the combustion chamber pressure is significantly different, such as KLl and Kl2.

Next, in order to examine the relationship between the combustion pressure waveform, ignition timing, EGR: l, and air-fuel ratio in more detail, we will examine the maximum combustion pressure value A determined from the combustion pressure, the crank angle B at which the combustion pressure reaches the maximum value, the rise, FIG. 9 shows the relationship between parameters such as the downward slope C1 heat generation amount D and the combustion duration E, and the ignition timing, EGRi, and air-fuel ratio. In FIG. 95, "large" indicates that the influence is large, and "small" indicates that the influence is small.

The following can be seen from Figure 9.

(1) Changing the EGR amount greatly affects the maximum combustion pressure value. When the EGR amount is increased, the maximum combustion pressure value becomes smaller. Therefore, if the maximum combustion pressure value is known, the EGR amount, NOx amount, torque, and fuel efficiency can be determined from a simple functional relationship as shown in FIG. 10, for example.

(2) When the EGR amount is increased, the crank angle at which the combustion pressure reaches its maximum value is delayed, so if the crank angle at which the combustion pressure reaches its maximum value is detected in an actual internal combustion engine, the EGR amount, N
Ox amount, torque, and fuel efficiency can be determined.

(3) Similarly, the E G Rr Jr., NOx amount, torque, and fuel consumption rate can be determined from the rising and falling slopes, combustion duration time, and heat release amount. Further, it will be more accurate if it is determined from a combination of two or more of the above-mentioned maximum combustion pressure, crank angle, rise, fall slope, combustion duration, and amount of heat generation.

(4) Maximize the combustion pressure by changing the air-fuel ratio16
, rise, fall slope, heat release amount, and combustion duration are greatly affected. However, in the commonly used air-fuel ratio range, the air-fuel ratio has little effect on the crank angle at which the combustion pressure reaches its maximum value.

Therefore, by detecting the maximum combustion pressure, rise, fall slope, combustion duration, and heat release amount, the air-fuel ratio, N
You can see changes in Ox proof, torque, and fuel efficiency.

(5) Maximum combustion pressure by changing the ignition timing,
Since the crank angle at which the combustion pressure reaches its maximum value varies greatly,
From these, the ignition timing, NOx amount, torque, and fuel efficiency can be determined.

Figure 11 shows that each parameter A-E of the two legs is torque, N
This table summarizes the amount of Ox and fuel efficiency.

As can be seen from Fig. 11, torque, NOx
You can know the changes in fuel consumption and fuel consumption rate.

Next, Figure 12 shows the EGR amount, air-fuel ratio, and
This shows the characteristics when changing the ignition timing in terms of NOx amount, torque, and fuel consumption rate.GM shows the EGR amount, G
N indicates the air-fuel ratio, and GQ indicates the change when the ignition timing is changed. Note that the vertical axis represents the amount of NOx emissions, the magnitude of torque, and the fuel efficiency rate.

The characteristics shown in FIG. 12 are characteristics at certain operating points, and have different values at other operating points. That is, to operate an internal combustion engine is to temporally connect the points of these characteristics -L.

In FIG. 12, even if the ignition timing is set to T17, for example, the NOx amount, torque, and fuel efficiency are not uniquely determined, and the EGR amount and air-fuel ratio are set to T12, for example.
By deciding T15, the N at that operating point is determined for the first time.
It determines the amount of Ox, torque, and fuel efficiency.

Operating an internal combustion engine depends on the operating conditions.
It is the accumulation of the characteristics shown in the figure, and even with the characteristics shown in Figure 12, the setting conditions for operating the internal combustion engine are T12 to T18.
There are countless others.

In order to determine these setting conditions, the conventional method is to know the operating average value at the operating point from the characteristics shown in FIG. 12, and then determine it based on the NOx amount, torque, and fuel consumption rate.

However, in the past, as mentioned above, it was difficult to know the combustion pressure waveform in real time, so when the type of internal combustion engine was completed, various tests were conducted to examine the characteristics shown in Figure 12 and determine the setting conditions. , we use a method that does not require modification once a decision has been made. For this reason, variations between solid parts of the internal combustion engine and changes over time are ignored, and as these cannot be corrected appropriately, combustion cannot be optimally controlled, which affects fuel efficiency and driving performance. This was causing a decrease in

However, in the present invention, as mentioned above, it is possible to accurately know the combustion pressure waveform in real time2, and the NOx amount, torque, and fuel efficiency can be determined from the A-H parameters based on this, so It is possible to accurately correct for variations and changes over time.

For example, in the GM shown in FIG. 12, initial values such as NOx amount Ml, torque M2, and fuel consumption rate M3 shown by solid lines are set to Mll, M21 . If it changes like M31,
Since the change can be known immediately, correction can be made immediately. For example, if the torque is to be used as a reference for correction, the EGR amount may be changed from T14 to T13.

The above explanation was about the EGR amount, but the air-fuel ratio,
Next, the control of the present invention will be explained based on the explanation in Section 1, in which the same thing can be done for the ignition timing.

FIG. 13 shows the operation of the arithmetic unit 17 of FIG. 1 by functional elements, and the same reference numerals as in FIG. 1 indicate the same elements.

In FIG. 13, 21 indicates various input signals S1 to S7 (
The pressure in the combustion chamber under each operating condition is measured mainly from the pressure signal 36), and from that value, the maximum value of combustion pressure, the crank angle at which the combustion pressure is maximum, the rising and falling slopes of combustion pressure, and heat generation are determined. A parameter calculation means 22 for calculating the amount and combustion duration, that is, at least one of the parameters A to E described above, stores at least one or a combination of two or more of the two parameters in a memory 23 ( By comparing the air-fuel ratio, ignition timing, and EGR rate of the internal combustion engine in a predetermined operating state with reference values stored in advance in a ROM (for example, ROM), the design target values (for example, in the case of air-fuel ratio, the stoichiometric air-fuel ratio In the case of ignition timing and EGR amount, deviations from the values determined by rotational speed and intake air amount), that is, deviations due to individual variations and changes over time, are detected, and the difference between the above parameters and the reference value is eliminated. learning means 25 for rewriting control target values for the air-fuel ratio, ignition timing, and EGR amount (for example, reference values for controlling the air-fuel ratio to match the stoichiometric air-fuel ratio) stored in the memory 24 (for example, RAM); is a control signal output means for outputting signals 39 to Sll for controlling at least one of the air-fuel ratio, ignition timing, and EGR amount in accordance with the above learned results.

The above signals 89 to 311 cause the fuel injection valve 9 in FIG.
, the recirculation amount regulator 12, and the ignition device 13, the air-fuel ratio, EGR amount, and ignition timing can be controlled to match the designed target values.

Next, FIG. 14 is an embodiment of a flowchart showing the calculation of the present invention, and shows a case where learning control is performed on the air-fuel ratio.

Note that the ignition timing and EGR amount can be controlled in exactly the same manner.

In FIG. 14, first, each input signal 5l-S7 is input to PI3.
Based on the various operating variables of the internal combustion engine, namely the rotational speed,
Measure the intake air amount and combustion chamber pressure.

At this time, if the measured values are calibrated using the method shown in FIG. 4, more precise control can be achieved.

Next, at P2O, the combustion pressure is calculated from the above-mentioned combustion chamber pressure by the method shown in the flowchart of FIG. 6 above. That is, the flowchart of FIG. 6 is included in P2O.

Next, in P21, each parameter is determined according to the method explained in FIG. seek.

Next, in P22, each of the above parameters is compared with a reference value (setting 1 reference value) using the method described in FIG. 11.12 above, and it is determined whether the deviation is larger than a predetermined value. By doing this, it is possible to detect whether the air-fuel ratio is larger or smaller than the design target value, for example, the stoichiometric air-fuel ratio, that is, whether it is biased toward the rich side or lean side as a whole.When the deviation is large in P22 Since the characteristics of the internal combustion engine may have changed from the characteristics at the time of design due to variations or aging, it is necessary to perform learning calculations. Therefore, the process first goes to P23, and it is determined whether the current driving state is acceleration or deceleration.

If YES in P2"3, that is, during acceleration/deceleration, operating variables such as the air-fuel ratio change suddenly, making it unsuitable for learning calculations, so go to P24, fix the control target value of the air-fuel ratio to a predetermined value, and perform learning calculations. Interrupt and return to PI3.

If No in P23, a learning calculation is performed.

First, in P25, the ignition timing and EG RM are fixed at predetermined values. This is because when performing air-fuel ratio learning calculations, changes in the air-fuel ratio cannot be accurately determined unless the ignition timing and EGR:i% are fixed.
Similarly, the other two parameters are fixed when performing the learning calculations on the quantities.

Next, in P26, the control target value of the air-fuel ratio is changed by a predetermined value (a small amount), and then the process returns to PI3.

In other words, the learning calculation involves checking the deviation between the parameters A-E and the reference value by changing the air-fuel ratio little by little under a constant operating condition, and then setting a new control target value when the deviation becomes less than a predetermined value. It is rewritten as a control target value.

For example, if the design target value of the air-fuel ratio is the stoichiometric air-fuel ratio, and as a result of comparing each parameter with the reference value, it is found that the air-fuel ratio as a whole is biased toward the richer side than the stoichiometric air-fuel ratio. If the control target value is moved to a value on the leaner side than the original target value, that is, the stoichiometric air-fuel ratio, the actual air-fuel ratio will shift toward the leaner side as a whole, so it is necessary to make it match the stoichiometric air-fuel ratio, which is the original design target value. I can do it.

If the characteristic changes as a result of changing the control target value in P26 as described above, and the deviation is smaller than the predetermined value in the comparison result of P22, the process goes to P27.

In P27, it is determined whether the number of measurements in which the deviation is smaller than a predetermined value is greater than or equal to a predetermined number. This is because if the number of measurements is small, errors due to noise and the like will increase, so to avoid this, measurements are repeated until a stable measurement value is obtained. This number varies depending on the type of internal combustion engine,
Determined by experiment for each type of internal combustion engine.

If No in P27, return to PI3 and repeat the measurement.

If YES in P27, the process goes to P28, where the air-fuel ratio control target value is rewritten to the value resulting from the learning calculation. By rewriting the control target value of the air-fuel ratio as described above, it is possible to control the actual air-fuel ratio to match the target value at the time of original design.

Incidentally, the ignition timing and EGR amount can also be controlled by learning in the same manner as described above.

By learning control as described above, the ignition timing, EG
Since the amount of R and the air-fuel ratio can be made to match the target values at the time of design, optimal control can always be performed without being affected by variations between individual units, that is, individual differences or changes over time.

(Effects of the Invention) As explained above, according to the present invention, the combustion pressure is determined from the combustion chamber pressure, and from that value, the combustion pressure maximum value, which has an important relationship to the combustion state of the internal combustion engine, and the combustion pressure maximum value are determined. By determining the crank angle, rise, downward slope, amount of heat generation, and combustion duration, and comparing these values with the reference value and detecting the difference, the ignition timing and EGR amount can be adjusted from the original target value. By detecting deviations in the air-fuel ratio and performing learning control to eliminate the above differences, it is possible to appropriately and effectively control the combustion state of the internal combustion engine regardless of individual differences or changes over time. Therefore, it has the effect of improving fuel efficiency, driving performance, and exhaust purification performance.

[Brief explanation of drawings]

FIG. 1 is a diagram of an embodiment of the internal combustion engine control device of the present invention, and FIG.
The figure is an example of a pressure sensor that detects the pressure in the combustion chamber.
The figure shows the relationship between the intake air amount and the combustion chamber pressure, Figure 4 is an example of a flowchart showing the calculation of the calibration method, Figure 5 is an example of the combustion chamber pressure waveform, and Figure 6 shows the relationship between the motoring pressure and the combustion chamber pressure. Flowchart of calculation for separating combustion pressure, No. 7
The figure is a waveform diagram for explaining the measurement of combustion pressure, Figure 8 is a waveform diagram showing changes in the combustion pressure waveform when changing the ignition timing, EGR amount, and air-fuel ratio, and Figure 9 is a waveform diagram for each parameter A-
Figure 10 shows the relationship between E and ignition timing, EGR amount, and air-fuel ratio. Figure 10 shows the relationship between maximum combustion pressure and EGR amount. Figure 11 shows the relationship between each parameter A-E and NOx amount, torque, and fuel efficiency. Figure 12 shows the amount of NOx, torque, fuel efficiency and ignition timing, E
FIG. 13 is a diagram showing the relationship between the GR amount and the air-fuel ratio, FIG. 13 is an embodiment of the arithmetic device of the present invention, and FIG. 14 is an embodiment of a flowchart showing the computation of the present invention. Explanation of symbols 1...Internal combustion engine body 2...Intake pipe 3...Exhaust pipe 4, φ, throttle valve 5...Throttle sensor 6, φO bypass pipe 7...Air amount regulator 8...・Intake air amount sensor 9...Fuel injection valve 10・Φ・Exhaust sensor 11...Exhaust recirculation pipe 12...Recirculation amount regulator 13...Ignition device 1411・Crank angle sensor 15・Fist・Water temperature Sensor 16... Intermediate pressure sensor 17... Arithmetic unit 18... Spark plug 19... Combustion chamber wall 20... Piezoelectric element 21... Parameter computing means 22... Slow learning 23... Memory 24- Memory 25... Control signal output means
8 (Omisakiwa Fig. 4 OT3eT4 2θ 1 1 1 1 1 1 Akebono 1U ( 379 Fig. 110 Fig. '1゛,. 8. [Procedure I] Period - Lη Procedural Amendment (White Patent Office Commissioner Kazuo Wakasugi 1, Indication of Case Patent Application No. 9928 of 1982 2)
, Title of the invention Control device between line machines 3, Relationship to the amended case Patent applicant name (399) Nissan Motor Co., Ltd. 4, Agent address (5 Marunouchi-chome, Chiyoda-ku, Tokyo 100)
No. 1 No. 5, Subject of amendment Detailed description of the invention in the specification and drawings. 6. Contents of amendment 1. Lines 5 to 9 of page 16 of the specification are amended as follows.

Claims (1)

[Claims] A means of measuring the pressure in the combustion chamber of an internal combustion engine, and from that value the maximum value of combustion pressure, the crank angle at which the combustion pressure is maximum,
Means for calculating at least one of the following parameters: rising slope, falling slope of combustion pressure, amount of heat generation, and combustion duration time, and based on at least one or a combination of two or more of the above parameters. a learning means for detecting a difference between the two and rewriting a control target value of at least one of the air-fuel ratio, ignition timing, and EGR amount of the internal combustion engine so as to eliminate the difference; A heating device comprising means for controlling at least one of an air-fuel ratio, ignition timing, and EGR amount according to the results.