JPH0339183B2 - - Google Patents

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 technology for controlling the combustion state of an internal combustion engine,
For example, the following are 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, Tokukai No. 1982-29209 is equipped with a device for electrically detecting the peak value generation timing of the pressure in the combustion chamber of an internal combustion engine and a device for electrically detecting the reference position of rotation angle of the crankshaft. The position where the pressure peak value occurs is detected using a crankshaft rotational angle reference position signal, and the ignition position is changed to make this the optimum position.

Furthermore, JP-A-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 certain predetermined value.

Furthermore, JP-A-52-77935 discloses an ignition timing control method that detects the difference between the maximum pressure of combustion gas and a predetermined standard setting pressure and controls the maximum pressure to match the standard setting pressure. are doing.

Furthermore, JP-A-52-151432 discloses that as the ignition timing advances, the ratio Pmax/Pm between the maximum combustion chamber pressure Pmax and the motoring pressure Pm tends to increase, and the MBT (minimum spark advancc for
(best torque), the ignition timing is adjusted to
Pm is controlled to be constant, and compared to conventional ignition timing control devices that program the average ignition timing based on test results of internal combustion engines, it is more effective at controlling atmospheric conditions, variations in internal combustion engine characteristics, etc. This method is superior in that it does not require any correction.

In addition, JP-A-53-60431 is the above-mentioned JP-A-52-60431.
Similar to the 151432, in an ignition timing control device that controls Pmax/Pm to 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 and intake pressure of the internal combustion engine, and Considering the variation in the ignition timing, it is possible to generate torque changes by periodically changing the ignition timing, determine the phase relationship between the changing phase of the ignition timing and the torque, and control the ignition timing based on the phase relationship between the two. By doing so, it is intended to operate the internal combustion engine at the minimum fuel consumption rate.

However, as mentioned above, in the conventional technology, the pressure in the combustion chamber is motoring pressure (the pressure generated when the gas in the combustion chamber is compressed by the up and down movement of the piston) and combustion pressure (the pressure generated by the combustion of the air-fuel mixture). and not identified. 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, various factors that are closely related to combustion, such as the maximum value of combustion pressure, the crank angle at which the combustion pressure is maximum, the rising slope and falling slope of combustion pressure, the amount of heat generation, and the combustion duration, are Because it was not possible to accurately detect parameters in real time, it was not possible to effectively compensate for internal combustion engine internal variations or changes over time, and it was not possible to individually control ignition timing, air-fuel ratio, and EGR amount. Because I was doing
There was a problem that sufficient performance could not be obtained in combustion control.

(Objective of the Invention) The present invention has been made to solve the above problems, and detects the parameters closely related to combustion during actual operation of an internal combustion engine, and controls combustion according to the values. The purpose is to provide a device that provides optimal control.

(Summary of the Invention) FIG. 15 is a block diagram showing the functions of the present invention.

In FIG. 15, 101 is a first means for measuring the pressure in the combustion chamber of the internal combustion engine, and is, for example, the pressure sensor 16 shown in FIG. 1, which will be described later. Also, the second means 1
In 02, by delaying the ignition timing until the combustion chamber pressure waveform obtained by the first method becomes a bimodal waveform, the waveform becomes only the motoring pressure before top dead center, and the waveform is changed at each crank angle. After top dead center, the motoring pressure waveform in the entire range is determined and stored by reproducing the motoring pressure waveform up to that point symmetrically with respect to top dead center, and then It is a means for determining combustion pressure by subtracting the value of the motoring pressure from the combustion chamber pressure for each crank angle, for example, the calculation means 17 shown in FIG. This corresponds to means 21, and its calculation contents are shown in the flowchart of FIG. 6, for example.
Further, the third means 103 is the second means 10
From the combustion pressure obtained in step 2, calculate the maximum value of combustion pressure, the crank angle at which the combustion pressure is maximum, the rising slope and falling slope of combustion pressure, the amount of heat generated in one combustion, and the combustion duration time. This also corresponds to the parameter calculation means 21 in FIG. 13. Further, the fourth means 104 compares at least one or a combination of two or more of the above-mentioned parameters with reference values to determine the output torque of the internal combustion engine and the NOx emissions in a predetermined operating state. It is a means for detecting a deviation from a standard value of fuel consumption and fuel consumption rate, for example, the calculation means 17 shown in FIG.
relative to. Further, the fifth means 105 is a means for controlling at least one of the air-fuel ratio, ignition timing, and EGR amount so as to eliminate the above-mentioned bias, and for example, the calculating means 17 in FIG.
This corresponds to the control signal output means 24 shown in the figure, the combustion injection valve 9, the recirculation amount regulator 12, the ignition device 13, etc. shown in FIG.

As mentioned above, in the present invention, instead of the combustion chamber pressure which is a combination of combustion pressure and motoring pressure as in the past, only the combustion pressure that directly indicates the combustion state is extracted, and the above-mentioned pressure obtained from that value is extracted. Since the above control is performed based on the parameters of and can be effectively controlled.

(Examples of the Invention) The present invention will be described in detail below based on Examples.

FIG. 1 is a diagram showing an embodiment of an internal combustion engine control device according to the present invention.

In FIG. 1, 1 is an internal combustion engine main body (a four-cylinder engine is shown), 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 adjusts the flow rate of intake air flowing through the bypass pipe 6 in accordance with the flow rate control signal S8.

Further, an intake air amount sensor (for example, an air flow meter) 8 outputs an intake air amount signal S1 corresponding to the amount of air taken into the internal combustion engine.

Further, a throttle sensor 5 interlocked with the throttle valve 4 outputs a throttle signal S2 corresponding to the opening degree of the throttle valve 4.

Further, a fuel injection valve 9 is provided at 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.

Furthermore, the exhaust pipe 3 and the intake pipe 2 are connected to the exhaust gas recirculation pipe 11.
connected via.

A recirculation amount regulator 12 is provided in the middle of this exhaust gas recirculation pipe 11, and controls the amount of exhaust gas recirculation according to a 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.

Further, the ignition device 13, which is controlled by the ignition signal S11, performs an ignition operation by applying a high voltage to a spark plug (not shown) provided for each cylinder.

The crank angle sensor 14 also outputs a unit angle signal S4 every time the crankshaft of the internal combustion engine rotates by a unit angle (for example, 1°), and outputs a reference angle signal S5 every time the crankshaft of the internal combustion engine rotates by a reference angle (180° for a four-cylinder engine). 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 this pressure sensor, for example, as shown in FIG.
A piezoelectric element 20 can be used which is pressed between the combustion chamber wall 19 and the combustion chamber wall 19 in the form of a washer.

Further, the arithmetic unit 17 includes, for example, a CPU, RAM,
It is composed of a microcomputer consisting of ROM, I/O, A/D converter, etc., and inputs signals S1 to S7 from each of the above sensors, performs various calculations, and outputs each of the above control signals S8 to S7. Output S11.

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 using various input signals S1 to S7.
The processing is performed by the arithmetic unit 17 according to the following.

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, and pressure sensors naturally need to operate properly within this temperature range.

However, pressure sensors composed of piezoelectric elements and strain gauges experience large temperature changes at high temperatures, and it has been extremely difficult to accurately compensate for this temperature change.

Furthermore, in devices that are used for many years, such as in automobiles, it is naturally expected that changes will occur over time, but it has been extremely difficult to accurately and automatically correct for this change.

However, the pressure in the combustion chamber and the amount of intake air are in a proportional relationship, and the temperature change range of the intake air is much narrower than that of the pressure sensor, so it is possible to calibrate the output of the pressure sensor 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 S1) and the output of the pressure sensor 16.

In Fig. 3, L1 indicates the combustion chamber pressure (the output itself of the pressure sensor 16), L2 indicates 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 relationship between L1 and L2 is The difference is the combustion pressure (the pressure created by the combustion of the air-fuel mixture).

Since the value of the combustion chamber pressure changes depending on the piston position, that is, the crank angle, ignition timing, EGR amount, and air-fuel ratio, the characteristics of L1 in Fig. 3 are as follows.
Shows values at specific crank angles and specific operating conditions.

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 in a certain operating state, so the pressure in the combustion chamber can be calibrated using the amount of intake air.

Also, as explained later, motoring pressure is proportional to the intake air amount regardless of the operating condition, so
If the motoring pressure can be separated from the 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 about 50° C. at most, and the temperature change range is much narrower than the temperature change range of the pressure sensor, so temperature correction of the intake air amount is easy.

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

In FIG. 4, first, at P1, the combustion chamber pressure at a specific crank angle is measured and stored while the ignition timing, EGR amount, and air-fuel ratio are constant.

As will be described later, when using the motoring pressure determined from the combustion chamber pressure, the ignition timing etc. do not need to be constant, but may be a value at a specific crank angle.

Next, at P2, the amount of intake air is measured and stored.

Note that this is not limited to the intake air amount, but may also be an equivalent operating variable such as intake negative pressure, throttle valve opening, etc.

Next, at P3, measure the intake air temperature (measured with a temperature sensor, such as a thermistor, installed in the intake pipe 2)
Then, the intake air amount determined in P2 is corrected to the reference temperature value.

Next, in P4, using the proportional relationship shown in Figure 3 above, the reference value determined in advance by experiment for that type of internal combustion engine, and the combustion chamber pressure and intake air amount determined in P1 and P3 are calculated. Compare with the corresponding relationship.

If the value of the combustion chamber pressure is biased towards the excessive side in P4, the process goes to P5 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 combustion chamber pressure is biased toward the small side in P4, the process goes to P6 and a correction is made to increase the pressure sensor value 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 the above calculation, 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 to GD indicate changes in the pressure waveform in the combustion chamber due to changing the ignition timing, and the ignition timing gradually becomes later from GA to GD. Also A1, B1,
C1 and D1 each indicate the entire combustion chamber pressure waveform, and A2, B2, C2, and D2 each indicate 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, due to its nature, the motoring pressure waveform
Since it is symmetrical with respect to TDC, it is possible to separate the motoring pressure and combustion pressure by using a waveform like GC or GD.

In other words, in the case of GC and GD waveforms, from the rising point of the waveform (corresponding to bottom dead center) T0 to top dead center TDC, only motoring pressure is stored, so this waveform is memorized, and after top dead center TDC, this waveform is stored. If this value is calculated symmetrically with respect to top dead center TDC, only the motoring pressure excluding the combustion pressure will be obtained, and by subtracting that value from the entire combustion chamber pressure, the combustion pressure will be determined.

The following will explain based on the GB and GC waveforms in FIG. 5 and the flowchart in FIG. 6.

In Fig. 6, first set the ignition timing at P7 to a position well before top dead center TDC, for example in Fig. 5 GB.
Set to T2 to create a single peak combustion chamber pressure waveform like GB.

Next, in P8, set α=α+1. This means that the ignition timing is delayed by a certain amount from the previous value.

Next, in P9, set the ignition timing to T2+α. P8
and P9, the ignition timing is delayed by a fixed amount for each calculation.

Next, at P10, the combustion chamber pressure is measured and stored for each crank angle. Note that this measurement is performed under the same operating conditions.

Next, in P11, check the previous measurement value (crank angle is T0
(closer to) Pb and 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 P8 and repeat the above procedure. If Pa<Pb, it indicates that at least one local maximum has occurred, so P12
go to

At P12, it is determined whether Pa continues to be smaller, that is, whether it has continuously decreased.

If YES in P12, it indicates that the characteristic is unimodal as shown in GB in FIG. 5, so return to P8 and repeat the above procedure.

If NO in P12, the process goes to P13, and it is determined whether there has been a change from small to large, that is, whether there has been a local minimum value.

If NO at P13, return to P8 and repeat as above.

If YES in P13, it indicates a bimodal characteristic as shown in the GC waveform in Figure 5, so go to P14.

In P14, it is determined whether the crank angle at which the minimum value occurs is after top dead center TDC.

If NO in P14, that is, if a local minimum value occurs before the top dead center TDC, this is an abnormal state that normally cannot occur, so the process goes to P17, and the number of times such a state has occurred is determined.

If it is less than a predetermined number of times (for example, 1 to 2 times) in P17, it is considered to be a measurement error, and the process returns to P8.

If this continues for a predetermined number of times or more, it is likely that more combustion has occurred or that an abnormality has occurred in the pressure sensor 16 or the like, so proceed to P18 and issue an abnormality alarm.

On the other hand, if YES in P14, the GC waveform is shown in FIG. 5, so the combustion pressure and motoring pressure are calculated in P15 and P16.

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

In the GC shown in Figure 5, T0 is 0 and top dead center TDC
If T1 is θ and T1 is 2θ, the motoring pressure waveform is symmetrical with respect to the top dead center TDC, so the top dead center
The motoring pressure Pm of crank angles T3 and T4, which are equidistant from TDC, is equal, and the pressure Pm of T4 (T4)
becomes Pm(T4)=Pmf(2θ−T4). Furthermore, Pmf
represents a function of pressure versus crank angle from 0 to θ.

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 (waveform C1) for each crank angle, the combustion pressure Pn can be obtained.

In addition, under the same operating conditions (same intake air amount),
Since the motoring pressure waveform is the same, once the motoring pressure is determined, advance the ignition timing to the normal advance value and subtract the above motoring pressure from the combustion chamber pressure at that time. The required combustion pressure can be determined.

In FIG. 6, Pm(K) (k is a variable indicating each crank angle) is obtained in P15, and Pn(K) is obtained in P16. Note that P(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. calibration can be easily and accurately performed.

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 diagram of the pressure waveform in the combustion chamber,
GE is the combustion chamber pressure waveform that is a combination of motoring pressure and combustion pressure, GF is the combustion pressure waveform, and GG is the
Indicates the integral value of GF. Also, in GE, the broken line E1
and solid line E2 indicate the pressure waveform in the combustion chamber when the ignition timing is changed, and E3 is the motoring pressure waveform. Furthermore, in GF and GG, the broken line waveform corresponds to E1, and the solid line waveform corresponds to E2.

In FIG. 7, first, the motoring pressure E3 is separated from the combustion chamber pressure waveform as shown in GE by the method described above, and then it is divided into E1 and E2.
By subtracting each from , the combustion pressure waveform shown in GF is obtained.

Next, from the GF waveform, the combustion pressure can be calculated using the well-known successive approximation method (a method of finding the peak by comparing adjacent values one after another) or by detecting the position where the differential value becomes zero. Find the maximum values FL1 and FL2 and their occurrence positions TDC and T8.

Also, the crank angle at which the GF waveform becomes 0 or more
The times τ1 and τ2 from T5 and T6 to the crank angles T7 and T9 returning to 0 are combustion duration times. To convert the crank angle into time, calculate the time it takes to rotate a unit crank angle (for example, 1°) from the internal combustion engine's rotational speed at that time, and add that value to T5~
Just multiply by the crank angle width of T7 or T6 to T9.

Further, the GG waveform is an integral of the GF waveform, and its maximum values G1 and G2 each indicate the amount of heat generation. Therefore, by finding the value of GG at T7 or T9, the respective heat release amounts can be obtained.

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

Even under the same operating conditions, the maximum value of the combustion chamber pressure and the combustion pressure determined from it, its crank angle, rising slope, falling slope, combustion duration, heat generation amount, EGR amount, air-fuel ratio, It changes by changing the ignition timing, etc., and depending on the value, the amount of NOx emissions, generated torque, fuel efficiency, etc. will 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. It becomes possible.

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

Figure 8 shows the EGR amount, air-fuel ratio, and
This shows the change in the pressure waveform in the combustion chamber when the ignition timing is changed.

First, GH is the waveform when changing the EGR amount,
When the EGR amount is increased from the initial state where the combustion chamber pressure is H1, the combustion chamber pressure changes to H2. Moreover, H3 is the motoring pressure waveform.

As can be seen from GH, increasing the amount of EGR slows down combustion, and the maximum pressure inside the combustion chamber decreases from HL1 to HL2.

To further clarify this change, GH' is a waveform in which only the combustion pressure is separated from the GH waveform.

In GH′, H11 corresponds to H1 of GH, and H12
corresponds to H2.

As can be clearly seen from the GH′ waveform, as the EGR amount increases, the maximum combustion pressure increases from HP11.
HP drops to 12, and the crank angle that occurs at the maximum value shifts significantly from TDC to T10.

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 isolated, as in GH'.

Next, GJ shows the change in the combustion chamber pressure waveform when the air-fuel ratio is changed, J1 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 combustion pressure reaches its maximum when the air-fuel ratio is around the stoichiometric air-fuel ratio (A/F = 14.8).
Regardless of whether the air-fuel ratio is richer or leaner than this point, the combustion pressure tends to decrease.

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 the changes in combustion chamber pressure and combustion pressure when the ignition timing is changed, and K1 and
K2 is the combustion chamber pressure waveform, and K3 is the motoring pressure waveform.

When the ignition timing is changed, the crank angle at which the combustion chamber pressure reaches its maximum value changes significantly from TDC to T11. Furthermore, even if the maximum value of combustion pressure is the same value KL11, the maximum value of combustion chamber pressure is KL1.
Much different like KL2.

Next, in order to examine the relationship between the combustion pressure waveform, ignition timing, EGR amount, 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 and fall Gradient C,
FIG. 9 shows the relationship between each parameter of heat generation amount D and combustion duration E, ignition timing, EGR amount, and air-fuel ratio.
In FIG. 9, "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 will greatly affect the maximum combustion pressure. As the EGR amount increases, the maximum combustion pressure value decreases. Therefore, if you know the maximum value of combustion pressure, you can calculate EGR amount, NOx, torque,
You can find the fuel efficiency rate.

(2) If the EGR amount is increased, the crank angle at which the combustion pressure reaches its maximum value will be 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, NOx amount, torque, fuel efficiency rate, etc. can be found.

(3) Similarly, rise, fall slope, combustion duration,
The amount of EGR, amount of NOx, torque, and fuel efficiency can also be determined from the amount of heat generated. In addition, the maximum combustion pressure, crank angle, rise, fall slope,
It will be more accurate if it is determined from a combination of two or more of the combustion duration and heat release amount.

(4) By changing the air-fuel ratio, the maximum combustion pressure, 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, changes in the air-fuel ratio, NOx amount, torque, and fuel efficiency can be known by detecting the combustion pressure maximum value, rise, fall slope, combustion duration, and amount of heat generation.

(5) By changing the ignition timing, the maximum value of combustion pressure and the crank angle at which the combustion pressure reaches its maximum value will change significantly, so from these changes the ignition timing, NOx amount,
Torque and fuel efficiency can be determined.

FIG. 11 shows the above-mentioned parameters A to E arranged in terms of torque, NOx amount, and fuel efficiency.

As can be seen from Fig. 11, each parameter A~
Changes in torque, NOx amount, and fuel efficiency can be known from at least one or a combination of two or more of E.

Next, Figure 12 shows the amount of EGR under certain operating conditions,
Characteristics when changing air-fuel ratio and ignition timing, NOx amount,
It shows torque and fuel efficiency, and GM
is the EGR amount, GN is the air-fuel ratio, and GQ is the change when changing the ignition timing. The vertical axis is NOx emissions,
Indicates the amount of torque and fuel efficiency.

The characteristics shown in FIG. 12 are characteristics at a certain operating point, and have different values at other operating points. In other words, operating an internal combustion engine means connecting these characteristic points over time.

In Fig. 12, for example, even if the ignition timing is set to T17, the NOx amount, torque, and fuel efficiency cannot be determined uniquely by that alone, but only by setting the EGR amount and air-fuel ratio to, for example, T12 and T15. The amount of NOx, torque, and fuel efficiency at that operating point are determined.

Operating an internal combustion engine involves accumulating the characteristics shown in Figure 12, which vary depending on the operating conditions.
Even with the characteristics shown in FIG. 12, there are countless setting conditions other than T12 to T18 for operating the internal combustion engine.

In order to determine these setting conditions, find out the operating average value at that operating point from the characteristics shown in Figure 12,
The conventional method was to determine the amount of NOx, torque, and fuel efficiency.

However, in the past, as mentioned above, it was difficult to know the combustion pressure waveform in real time, so various tests were conducted when the type of internal combustion engine was completed.
A method is used in which the characteristics corresponding to those shown in the figure are examined to determine the setting conditions, and once determined, no changes are made. For this reason, variations among solids in the internal combustion engine, changes over time, etc. are ignored, and it is not possible to properly correct for these, making it impossible to optimally control combustion. was causing a decline in

However, in the present invention, as mentioned above, the combustion pressure waveform can be accurately known in real time, and the NOx amount can be determined from the parameters A to E based on it.
Since you can know the torque and fuel consumption rate, you can accurately correct changes over time.

For example, in the GM in Figure 12, the solid line indicates
When initial values such as NOx amount M1, torque M2, and fuel efficiency rate M3 change as shown by broken lines M11, M21, and M31, the change can be immediately known and correction can be made immediately. For example, if you are correcting based on torque, change the EGR amount from T14.
All you have to do is change it to T13. The above explanation is
Although this was done for the EGR amount, the same thing can be done for the air-fuel ratio and ignition timing.

Based on the above explanation, the control of the present invention will now be explained.

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
The combustion chamber pressure in each operating state is measured from ~S7 (mainly pressure signal S6), and from that value, the maximum value of combustion pressure, the crank angle at which the combustion pressure is maximum, the rising slope and falling slope of the combustion pressure,
Parameter calculation means 22 calculates the amount of heat generation and combustion duration, that is, at least one of the parameters A to E described above, and a memory 23 ( Deviations from the standard values of the internal combustion engine's output torque, NOx emissions, and fuel efficiency in a given operating state can be determined by comparing them with standard values (e.g., design standard values) stored in advance in a ROM (for example, ROM). 24 is a comparison means for detecting the air-fuel ratio, ignition timing, and EGR to eliminate the above bias.
signals S9 to S11 controlling at least one of the quantities;
This is a control signal output means for outputting.

By controlling the fuel injection valve 9, the recirculation amount regulator 12, and the ignition device 13 shown in FIG. 1 using the above signals S9 to S11, the air-fuel ratio, EGR amount, and ignition timing are adjusted, and the NOx amount, torque, and The fuel efficiency rate can be controlled to match the design standard value.

Next, FIG. 14 is an embodiment of a flowchart showing the calculation of the present invention.

In FIG. 14, first, in P19, the pressure in the combustion chamber is measured based on the pressure signal S6 and the like.

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

Next, in P20, the combustion pressure is calculated from the above combustion chamber pressure by the method shown in the flowchart of FIG. 6 above. In other words, the flowchart shown in FIG. 6 is included in P20.

Next, in P21, each parameter, namely the maximum combustion pressure value A, the crank angle B at which the combustion pressure reaches the maximum value, the rising and falling slopes C, the heat release amount D, and the combustion Find the duration E.

Next, in P22, by comparing each of the above parameters with the reference values using the method explained in Figs. (characteristics of).

Next, in P23, the above bias is eliminated by the method explained in FIG. 12 above. For example, the first
In the GM shown in FIG. 2, the value of the recirculation amount control signal S10 is changed to reduce the EGR amount from T14 to T13 in order to match the torque.

By doing the above, the amount of NOx, torque, and fuel efficiency can be made to match the reference values at the time of design, so optimal control can always be performed without being affected by 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 maximum combustion pressure, which has an important relationship to the combustion state of the internal combustion engine, is determined. By determining the crank angle, rise, fall slope, amount of heat generation, and combustion duration, and controlling the ignition timing, EGR amount, and air-fuel ratio to eliminate deviations between these values and the reference value. Since it is possible to match torque, NOx, and fuel efficiency to the standard values at the time of design, it is possible to always appropriately and effectively control the combustion state of the internal combustion engine without being affected by changes over time, etc. Therefore, there is an effect that fuel efficiency, driving performance, and exhaust purification performance can be improved.

[Brief explanation of drawings]

FIG. 1 is a diagram of an embodiment of the internal combustion engine control device of the present invention, FIG. 2 is a diagram of an example of a pressure sensor for detecting combustion chamber pressure, FIG. 3 is a diagram of the relationship between intake air amount and combustion chamber pressure, and FIG. Figure 4 is an example of a flowchart showing calculations in the calibration method, Figure 5 is an example of a combustion chamber pressure waveform, Figure 6 is a flowchart of calculations to separate motoring pressure and combustion pressure, and Figure 7 is a flowchart of calculations to separate motoring pressure and combustion pressure. 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. Figure 9 is a waveform diagram for each parameter A to E. A diagram of the relationship between ignition timing, EGR amount, and air-fuel ratio. Figure 10 is a diagram of the relationship between maximum combustion pressure and EGR amount. Figure 11 is a diagram of each parameter A to E and NOx.
Figure 12 is a diagram of the relationship between quantity, torque, and fuel consumption rate.
NOx amount, torque, fuel efficiency and ignition timing, EGR amount,
FIG. 13 is an embodiment of the calculation device of the present invention; FIG. 14 is an embodiment of a flow chart showing the calculation of the invention; FIG. 15 is a diagram showing the functions of the invention. It is a block diagram. Explanation of symbols, 1... Internal combustion engine body, 2... Intake pipe, 3... Exhaust pipe, 4... Throttle valve, 5...
Throttle sensor, 6...Bypass pipe, 7...Air amount regulator, 8...Intake air amount sensor, 9...Fuel injection valve, 10...Exhaust sensor, 11...Exhaust recirculation pipe, 12...Return Flow rate regulator, 13... Ignition device, 14... Crank angle sensor, 15... Water temperature sensor, 16... Pressure sensor, 17... Arithmetic device,
18... Spark plug, 19... Combustion chamber wall, 20...
... Piezoelectric element, 21 ... Parameter calculation means, 22
. . . Comparison means, 23 . . . Memory, 24 . . . Control signal output means.

Claims (1)

[Claims] 1. A first means for measuring the pressure in the combustion chamber of an internal combustion engine, and a method for delaying the ignition timing until the pressure waveform in the combustion chamber obtained by the first means becomes a bimodal waveform. Then, before top dead center, the waveform is made up of only the motoring pressure, and its value is memorized for each crank angle.
After top dead center, the motoring pressure waveform in the entire range is obtained and stored by reproducing the previous motoring pressure waveform symmetrically with respect to top dead center, and then the value of the motoring pressure is stored. a second means for determining the combustion pressure by subtracting it from the combustion chamber pressure for each crank angle; and a maximum value of the combustion pressure from the combustion pressure determined by the second means; a crank for which the combustion pressure is maximum; a third means for calculating at least one of the following parameters: angle, rising slope and falling slope of combustion pressure, amount of heat generated in one combustion, and combustion duration time; and at least one of the above-mentioned parameters. A fourth method for detecting deviations from reference values in output torque, NOx emissions, and fuel efficiency of the internal combustion engine in a predetermined operating state by comparing one or a combination of two or more with reference values. The air-fuel ratio, ignition timing,
A control device for an internal combustion engine, comprising: fifth means for controlling at least one amount of EGR.