JPH0711266B2 - Control device for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine that controls an ignition timing according to a detection result of knocking of the internal combustion engine.

[Conventional technology]

Generally, in an internal combustion engine, due to rapid combustion due to early ignition of unburned air-fuel mixture in the cylinder, the cylinder pressure is determined by a plurality of natural frequencies determined by the cylinder size (in particular, its bore diameter) and the combustion temperature. The (cylinder pressure) undergoes damped vibration, and this damped vibration may cause a so-called knocking phenomenon in which the internal combustion engine produces a metallic tapping sound.

Therefore, conventionally, for example, JP-A-54-142425 and JP-A-
As described in Japanese Patent Laid-Open No. 56-554, there is a control device for an internal combustion engine that controls the ignition timing according to the detection result of knocking to avoid knocking.

Such a control device for an internal combustion engine uses a detection signal output from a knocking sensor such as a pressure sensor mounted on a cylinder block of the internal combustion engine or as a washer of an ignition plug to detect a specific frequency band (about 5 to 6 KHz) related to the knocking.
The above signals are extracted, predetermined signal processing is performed to generate a detection signal corresponding to the combustion pressure oscillation of the engine, and the detection signal is compared with a predetermined reference level to determine the presence or absence of knocking. The ignition timing is retarded and advanced based on the determination result.

[Problems to be solved by the invention]

However, statistically, the correlation between the detection result of the combustion pressure oscillation of the engine (output of the knocking sensor) and the generated knocking, that is, trace knock, light knock, medium knock, heavy knock, is not constant, and for example, during trace knock. The power level of each combustion pressure oscillation at the time of light knock and that at light knock almost overlap each other.

Therefore, depending on the method of setting the reference level to be compared with the detection signal of the combustion pressure oscillation, even the trace knock, which has no audible problem, is detected as problematic knocking, and the ignition timing is retarded to control the fuel consumption. May occur and the generated torque may decrease, but the accuracy of detecting the light knock, which is a problem in hearing, may decrease.

In this way, if the ignition timing is controlled by directly comparing the detection result of the combustion pressure oscillation of the engine with the reference value and determining the presence or absence of knocking, it is possible to detect the problematic knocking with high accuracy and obtain an accurate ignition. It may not be possible to control the timing.

[Means for solving problems]

Therefore, the control device for the internal combustion engine according to the present invention is
As shown in the figure, a combustion pressure oscillation detecting means A for detecting combustion pressure oscillation of the internal combustion engine, and a first determination for determining whether or not a small knocking occurs based on the detection result of this combustion pressure oscillation detecting means A Means B and this first judging means B
An occurrence frequency determining means C for determining the occurrence frequency of knocking by comparing the occurrence interval from the occurrence of a small knocking to the occurrence of the next knocking with the frequency determination value at the time of trace knocking based on the determination result of Second determination means D for determining whether or not knocking larger than the reference value has occurred based on the detection result of the pressure vibration detection means A.
Based on the detection result of the frequency generating means C, the first correction amount determining means E for determining the correction amount of the ignition timing so as to have the occurrence frequency at the time of the trace knock, and the determination of the second determining means D. Second correction amount determining means F for determining the correction amount of the ignition timing as a value proportional to the deviation with respect to the reference value based on the result, and first and second correction amount determining means E, F for these.
Ignition timing control means G for controlling the ignition timing based on the determination result of

[Operation] By comparing the occurrence frequency of small knocking with the occurrence interval of the small knocking and the frequency determination value at the time of trace knocking, it is possible to determine with the minimum occurrence of knocking, and the occurrence frequency of trace knocking based on the frequency determination result. By correcting the ignition timing so that the engine output is controlled to a trace knock level that is advantageous for engine output and has no auditory problem, it is possible to improve drivability.

On the other hand, when large knocking occurs, the ignition timing is immediately corrected by the correction value proportional to the deviation from the reference value, so that the deterioration of the acceleration performance can be prevented.

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

FIG. 2 is an overall schematic configuration diagram of a control device for an internal combustion engine embodying the present invention.

In this internal combustion engine, an air-fuel mixture obtained by mixing the air taken into the intake manifold 4 via the air cleaner 1, the air flow meter 2 and the throttle valve 3 with the fuel supplied by the injector 5 is generated. Is ignited by the ignition plug 7 and burned, and the exhaust gas generated by this combustion is discharged from the exhaust pipe through the catalytic converter 8 and the muffler 9.

On the other hand, in the control unit 11 which controls the whole,
Detects the intake air flow rate signal from the air flow meter 2, the throttle valve position signal from the throttle switch 12 that detects the opening of the throttle valve 3, the rotation signal from the crank angle sensor 13, and the neutral position of the transmission 14. The neutral signal from the neutral switch 15 and the vehicle speed signal from the vehicle speed sensor 16 are input.

Further, the fuel temperature signal from the fuel temperature sensor 17 for detecting the fuel temperature, the oxygen concentration signal from the O ₂ sensor 18 for detecting the oxygen concentration in the exhaust gas, and the water temperature signal from the water temperature sensor 19 for detecting the cooling water temperature are Is entered.

Further, a cylinder pressure sensor for detecting combustion pressure oscillation of the engine 6
The in-cylinder pressure signal from 21 is input.

Then, the control unit 11 drives and controls the injector 5 to control the fuel supply amount on the basis of these input signals and various data stored therein, and an ignition unit for supplying a high voltage to the ignition plug 7. Ignition is controlled by intermittently controlling the primary current of the coil 22.

Also, the AAC valve 23 is drive-controlled to control the throttle valve 3
Control the air flow rate that bypasses, control the idle speed, control the VCM valve 24, control the EGR valve 25, and control the EG
Control the amount of R.

In FIG. 2, 26 is a fuel pump, 27 is a canister, 28 is a BC valve, and 29 is a check valve.

3 and 4 are a block diagram and a functional block diagram showing the configuration of the control unit 11 in the control device for the internal combustion engine.

First, the in-cylinder pressure sensor 21 is a piezoelectric conversion type pressure sensor, and as shown in FIGS.
It is attached as a washer of the ignition plug 7 attached to 6A, and outputs the charge signal S ₁ according to the cylinder internal pressure (cylinder internal pressure) of the internal combustion engine 6 as described above.

Further, the crank angle sensor 13 outputs the reference signal S ₂ every time the engine rotates by a predetermined angle, for example, every 120 degrees of the crank angle in a 6-cylinder engine (180 degrees of the crank angle in a 4-cylinder engine), and Position signal S ₃ every 1 or 2 degrees
Is output.

It should be noted that the position signal S ₃ may be output for each other angle such as 0.1 degrees, and the thinner the position signal S ₃ , the higher the control accuracy.

On the other hand, the charge amplifier 31 of the control unit 11
For example, as shown in FIG. 6, the op-amp OP ₁ , resistances R ₁ , R ₂ ,
After converting the charge signal S ₁ from the in-cylinder pressure sensor 21 into a voltage signal by the charge-voltage conversion circuit including the capacitor C ₁ and the diodes D ₁ and D ₂ , the voltage signal is converted into an operational amplifier OP ₁ and a resistor.
The amplified signal is amplified by the amplifier circuit composed of R _{3 to} R ₈ and the diode D ₃ and output as the detection signal S ₄ .

The bandpass filter 32 extracts only the signal component of the predetermined frequency, that is, the frequency band (about 6 to 17 KHz) related to knocking from the detection signal S ₄ from the charge amplifier 31, and the extracted signal component is detected signal S ₅ Output as.

The non-knock vibration energy detection circuit 33 is a clan angle sensor.
The bandpass filter corresponding to the combustion pressure oscillation of the engine is timed by the reference signal S ₂ and the position signal S ₃ from the 13
This is a circuit that generates a value (correlation value) correlated with the combustion pressure oscillation energy when no knocking is occurring from the detection signal S ₄ from 32 (non-knocking), for example, the generated correlation value (integral value). Is output as an integrated signal S ₆ .

The knocking vibration energy detection circuit 34 is also timed by the reference signal S ₂ and the position signal S ₃ from the clan angle sensor 13, and from the detection signal S ₄ from the bandpass filter 32 corresponding to the combustion pressure vibration of the engine. It is a circuit that generates a value (correlation value) correlated with the combustion pressure oscillation energy during knocking, for example, an integral value, and outputs the generated correlation value (integral value) as an integral signal S ₇ .

As shown in FIG. 7, the non-knock vibration energy detecting circuit 33 includes an absolute value integrator 33A for performing an absolute value integration on the detection signal S ₅ from the bandpass filter 32, resetting and holding the integrated value, and a predetermined value. The value corresponding to the crank angle of is preset and the reference signal from the crank angle sensor 13
It comprises presettable counters 33B, 33C for counting the position signal S ₃ according to S ₂ , and a flip-flop circuit 33D for controlling the operation of the integrator 33A according to the outputs of these counters 33B, 33C.

On the other hand, as shown in FIG. 7, the knocking vibration energy detecting circuit 34 has the same absolute value integral value 34A as the non-knocking vibration energy detecting circuit 33, and presettable counters 34B and 34C.
And a flip-flop circuit 34D.

Here, the present invention is applied to a 6-cylinder engine, and each of the presettable counters 33 of the non-knock vibration energy detection circuit 33 and the knock vibration energy detection circuit 34 is used.
B, 33C and 34B, 34C are the reference signals of the crank angle sensor 13.
S ₂ is set to be before TDC 70 ° compression, before and after the top dead center 40
The following values are preset to detect the vibration energy during non-knocking and during knocking.

Counter 33B: Crank angle equivalent to 30 degrees Counter 33C: Crank angle equivalent to 70 degrees Counter 34B: Crank angle equivalent to 70 degrees Counter 34C: Crank angle equivalent to 120 degrees Pre-settable counter of knocking vibration energy detection circuit 34 34C output (output at crank angle 110 degrees)
The external interrupt request signal SI for the main control circuit 35 described later.
Output as NT.

FIG. 8 shows an example of the absolute value integrator 33A of the non-knock vibration energy detection circuit 33.

In this integrator 33A, the analog switch A controlled by the output S ₈ from the flip-flop circuit 33D shown in FIG.
S is turned on when its output S ₈ is “L”.

As a result, the detection signal S ₅ from the bandpass filter 32 input through the analog switch AS is amplified by the amplifier circuit including the operational amplifier OP ₃ , resistors R _{10 to} R ₁₄ and capacitor C ₂ .

Then, the amplified detection signal is supplied to the operational amplifier OP ₁ and the resistor.
R ₁₅ to R _18, a capacitor C _3, a diode D _4, by connexion to half-wave rectifier to half-wave rectifier circuit consisting of D _5.

After that, the half-wave rectified output of this half-wave rectifier circuit and the amplified detection signal are combined by an integrator circuit composed of an operational amplifier OP ₅ , resistors R _{19 to} R ₂₂ , a capacitor C ₄ , and a zener diode ZD (resultant (Same as full-wave rectification), and the integrated value is output as integrated signal S ₆ .

When the analog switch AS is turned off, the integrated value at that time is held.

Further, when the reference signal S ₂ from the crank angle sensor 13 is input, the reset circuit composed of the resistor R ₂₃ and the transistor Q ₁ is activated, that is, the transistor Q ₁ is turned on and both ends of the capacitor C ₄ are connected. Short and condenser C ₄
The electric charge held at is discharged (reset state).

The absolute value integrator of the knocking vibration energy detection circuit 34
34A has the same configuration and operation, the description thereof will be omitted.

Returning to FIG. 3, the main control circuit 35 includes a CPU 36, a ROM 37, and a RAM 38.
And a microcomputer including I / O 39 having an A / D converter and the like built therein.

The main control circuit 35 includes a reference signal S ₂ and a position signal S ₃ from the crank angle sensor 13, an integration signal S ₆ from a non-knock vibration energy detection circuit 33, and an integration signal from a knock vibration energy detection circuit 34. Signal S ₇ and external interrupt request signal SINT,
Various detection signals as described above with reference to FIG. 2 are input.

Then, the processing related to the ignition timing control such as the determination of the knocking level, the determination of the frequency, the determination of the correction amount of the ignition timing, the determination of the ignition timing, etc., which are generated based on these respective input signals, is performed, and the processing result is obtained. Based on this, the power transistor 41 of the ignition device 40 is turned on / off to control the ignition timing.

The control of the ignition timing (ON / OFF control of the power transistor 41) corresponds to the ignition timing determined in the advance value (ADV) register and the dwell angle (DWELL) register (not shown) provided inside the I / O 39. Value (advance value, dwell angle)
Is set, the values of these registers are compared with the value of the counter that counts the position signal S ₃ , and when they match, the power transistor 41 is turned on or off.

Further, the ignition device 40 has an ignition coil which is controlled by turning on / off the power transistor 41.
The primary current of 22 is interrupted to generate a high voltage on the secondary side thereof, and this high voltage is applied to the spark plug 7 to ignite spark ignition.

The function relating to the ignition timing control of the main control circuit 35 will be described with reference to the function block of FIG.

First, the ratio calculation unit 35 is a non-knock vibration energy detection circuit.
Integral signal S ₆ from 33 and vibration energy detection circuit at knock 34
A ratio (or a difference) with the integrated signal S ₇ from is calculated, and this is output as the detected value of the combustion pressure oscillation.

That is, in this embodiment, the in-cylinder pressure sensor 21, the charge amplifier 31, the band pass filter 32, the non-knock vibration energy detection circuit 33, the knock vibration energy detection circuit 34, and the ratio calculation section 35A are used to perform the combustion of FIG. Pressure vibration detection means A
Are configured.

The determination unit 35B uses the detected value of the combustion pressure oscillation from the ratio calculation unit 35A as the first reference value generation unit 35C and the second reference value generation unit 3C.
Compared to each first and second reference value from 5D,
Judgment as to whether or not the generated knocking is a minor one,
It judges the occurrence frequency of slight knocking and judges whether the generated knocking is large or not, and outputs each judgment result.

That is, the determination unit 35B, the first reference value generation unit 35C, and the second reference value generation unit 35D are used to determine the first determination unit B, the frequency determination unit C, and the second determination unit in FIG. It constitutes a means D.

The first and second reference value generators 35C and 35D are connected to the main control circuit 3
It consists of the table stored in ROM 37 of 5.

The correction amount determination unit 35E constitutes the first and second correction amount determination means E and F of FIG. 1, and the ignition timing based on the determination result of the slight knocking occurrence frequency based on the determination result of the determination unit 35B. Of the ignition timing and the correction amount of the ignition timing based on the determination result of the large knocking.

The ignition timing control unit 35F constitutes the ignition timing control means G of FIG. 1 and corrects the ignition timing determined based on the intake air amount, the engine speed, etc. by the correction amount determined by the correction amount determination unit 35E. The ignition device 40 is controlled according to this result.

The main control circuit 35 also performs control other than control related to ignition timing, but detailed description thereof will be omitted.

Further, in the above description, the cylinder pressure sensor 21 and the charge amplifier.
Although 31 is shown only for one cylinder, it is actually provided for each cylinder, and the output of each charge amplifier 31 is switched by a multiplexer to be input to the bandpass filter 32.

Similarly, the ignition device 40 is provided for each cylinder, or the power transistor 41 and the ignition coil 22 of the ignition device 40 are made common to each cylinder, and the high voltage generated in the ignition coil 22 is distributed by the distributor. Then, it is distributed to each spark plug 7.

Next, the operation of this embodiment thus configured will be described with reference to FIG. 9 and subsequent figures.

First, the principle of detecting knocking in this embodiment will be described.

First, the power spectrum of in-cylinder pressure oscillation is, for example,
As shown in the figure, the line I is shown when the knock is not performed, and the line II is shown when the knock has a relatively large level.

Note that this is the full load for an internal combustion engine with four cylinders of 1800cc, 4
The experiment results by the applicant when the engine is operated at 800 RPM have been confirmed to be substantially the same for other internal combustion engines.

As can be seen from FIG. 9, there is a large difference in power level between the knocked state and the non-knocked state in the frequency band of 6 to 17 KHz.

Therefore, by converting the charge signal of the in-cylinder pressure sensor into a voltage signal and extracting the signal component in the above frequency band from this signal, for example, in the non-knock time and the knock time,
A signal (hereinafter referred to as an “extracted signal”) as shown in FIGS. 11A and 11B is obtained. It should be noted that these show waveforms of high-frequency vibration of the in-cylinder pressure.

Here, the power of the signal x (t) in the specific frequency band is generally It is represented by. That is, it is obtained as the time average of the square of the signal amplitude.

Therefore, considering the integral of the absolute value of the signal shown in FIG. 10, Becomes

The right side of this equation is the RMS (root mean square) of the signal x (t)
Therefore, the left side of this equation can be considered as an amount indicating the power of the signal x (t), or at least an amount having a single valence correlation with the power.

In addition, here, it is assumed that the signal of the first expression and the signal of the second expression x (t) are signals having a single frequency, but it may be practically used even if the signals include a plurality of frequency components.

Therefore, the extracted signal at the time of non-knock shown in FIG.
Crank angle from 40 degrees before top dead center (BTDC40 °) to top dead center (TD
When absolute value integration is performed for the range up to C), the integrated signal is as shown in FIG. 11 (a), for example.

Similarly, when the extracted signal at the time of knock shown in Fig. 10 (b) is integrated by absolute value in the range from top dead center to 40 degrees after top dead center (ATDC 40 degrees) at crank angle, the integrated signal is For example, it becomes as shown in FIG.

Each of these integrated signals corresponds to in-cylinder pressure vibration energy in the crank angle range. That is, the term of (1 / 2T) is dropped in the above equation.

As can be seen from FIG. 11 (a), in the non-knock state, the integrated signal increases almost linearly, and constant amplitude energy always exists regardless of the crank angle. That is, at non-knock time, set TDC to T = 0, The relationship is established.

On the other hand, as can be seen from Fig. 11 (b), at the time of knocking, TD
In the expansion stroke after C, the energy increment due to knotting appears.

By the way, it is generally considered that the determination of the knock level by human hearing is made based on the relative strength difference between the sound pressure level caused by the background noise that is constantly generated and the sound pressure level caused by the knocking vibration. ing.

Therefore, if the vibration energy of the in-cylinder pressure at the time of non-knocking and the energy of the vibration of the in-cylinder pressure at the time of knocking are directly compared, it is possible to detect the knocking level that is in good agreement with the sensory surface.

Here, according to the above equation, it can be empirically considered that no knocking occurs before top dead center, so the integrated signal before top dead center determines whether or not knocking occurs after top dead center. Regardless of this, it can be said that it is the predicted value of the vibration energy of the in-cylinder pressure in the expansion stroke after top dead center when the engine is not knocked.

Therefore, the (rectified) integral value of the in-cylinder pressure vibration within the predetermined crank angle range before top dead center and the predetermined crank angle range after top dead center or within a predetermined range including the range before top dead center By comparing the (rectified) integral value of the in-cylinder pressure vibration, the vibration energy of the in-cylinder pressure at the time of non-knock and the vibration energy of the in-cylinder pressure during the combustion stroke are directly compared. It is possible to detect a knocking level that matches well.

According to various experiments by the present applicant, it can be considered that the relationship shown in FIG. 11 is established under almost all operating conditions.

However, the integration interval must be selected so that the relation of the equation (3) does not hold due to the influence of the vibration of the spark plug caused by the vibration of the seating / seating of the intake / exhaust valve. (In this case, 40 degrees before and after TDC is selected).

Next, operations of the non-knock vibration energy detection circuit 33 and the knock vibration energy detection circuit 34 for performing such processing will be described with reference to FIG. 12 (hereinafter referred to as “the same drawing”). .

First, in the vicinity of the crank angle of 0 to 120 degrees, the charge amplifier 31 outputs a detection signal S ₄ as shown in FIG. 3C, and the detection signal S ₄ passes through the band pass filter 32, so that, for example, A detection signal (extraction signal) S ₅ as shown in FIG. 9D is input to the non-knock vibration energy detection circuit 33 and the knock vibration energy detection circuit 34. Note that, here, the detection signal S ₅ contains a knock component.

On the other hand, the integrators 33A and 34A of the non-knock vibration energy detection circuit 33 and the knock vibration energy detection circuit 34 are output from the crank angle sensor 13 at 70 degrees before compression top dead center (BTDC 70 degrees). Time t ₁ when the reference signal S ₂ shown in b) is input
Is reset.

Moreover, each counter 33B, 33C, 34B, 34C, at the same time is Purisetsuto is Purisetsuto value described above, the count of the position signal S ₂ shown in FIG output from the time t ₁ from the crank angle sensor 13 (b) Start.

Then, at the time t ₂ when the crank angle reaches 30 degrees, the output of the counter 33B of the non-knock vibration energy detection circuit 33 is inverted, and as shown in FIG.
The output S _{8 of} is inverted (becomes “L”).

As a result, the reset state of the integrator 33A is released, and the bandpass filter 32 starts the absolute value integration of the detection signal S ₅ .

After that, at the time t ₃ when the crank angle reaches 70 degrees, the counter 33C
Output is inverted and the output of the flip-flop circuit 33D S ₈
Is inverted (becomes “H”).

And I connexion, integrator 33A is held until time t ₅ that the integrated value of the time t ₃ the reference signal S ₂ is inputted.

Therefore, the integrator 33A outputs an integrated signal S ₆ corresponding to the vibration energy in the non-knock state, as shown in FIG.

On the other hand, in Natsuta time t ₃ to the crank angle of 70 degrees, the output of the counter 34B of Notsuku during vibration energy detection circuit 34 is inverted, the flip-flop circuit 34D as shown in FIG. (H)
The output S _{9 of} is inverted (becomes “L”).

As a result, the reset state of the integrator 34A is released, and the absolute value integration of the detection signal S ₅ from the bandpass filter 32 is started.

After that, at the time t ₄ when the crank angle reaches 110 degrees, the counter 34C
Output is inverted and the output of flip-flop circuit 34D S ₉
Is inverted (becomes “H”).

Accordingly, the integrator 34A holds the integrated value at the time point t ₄ until the time point t ₅ when the reference signal S ₂ is input.

Therefore, the integrator 34A outputs an integrated signal S ₇ corresponding to the vibration energy at the time of knocking, as shown in FIG.

Next, the knocking determination / correction amount determination processing executed by the CPU 36 of the main control circuit 35 will be described with reference to FIGS. 13 and 14.

When the CPU 36 of the main control circuit 35 requests an external interrupt by the external interrupt request signal SINT from the knocking vibration energy detection circuit 34 (crank angle 70 degrees as described above).
Then, the execution of the knocking determination / correction amount determination processing is started.

Then, in STEP 1, the integrated signal S ₆ from the non-knock vibration energy detection circuit 33 is sent to the A / D converter built in the I / O 39.
The start of A / D conversion is commanded to start A / D conversion of the integrated signal S ₆ .

Then, in STEP2, the first reference value SL1 corresponding to the engine speed at that time is selected from the _first reference value table stored in ROM37 and read out, and in STEP3, the second reference value table also stored in ROM37 is selected. A second reference value SL ₂ corresponding to the engine speed at that time is selected and read.

The engine speed is obtained by counting the position signal S ₃ from the crank angle sensor 13 for a predetermined time in a process (not shown), and storing the count value at a predetermined address of the RAM 38 as the engine speed.

After that, in STEP 4, it is determined whether the A / D conversion of the integrated signal S ₆ is completed, and when the A / D conversion is completed, in STEP 5, the conversion result is the amount B related to the vibration energy in the non-knock state. Is stored in the RAM 38 at a predetermined address.

Next, in STEP ₆ , A / D conversion of the integrated signal S ₇ from the knocking vibration energy detection circuit 34 is started, and in STEP 7, it is determined whether or not the A / D conversion is completed, and the A / D conversion is completed. In that case, in STEP8, the conversion result is stored in a predetermined address of the RAM 38 as a quantity K related to the vibration energy at the time of knocking.

Then, in STEP 9, the amount B and the amount K obtained by the above-described processing are read out, the ratio K / B (or the difference K−B may be used) is calculated, and the amount K is normalized. The calculation result will be referred to as "K / B value" below.

Here, the first and second reference values SL ₁ and SL ₂ will be described.

First, the distribution of cumulative frequencies of K / B values for various knocking phenomena in a 6-cylinder engine is as shown in FIG.

In other words, the distribution of the cumulative frequency of K / B values at the time of non-knock is the line I.
Then, the distribution of the cumulative frequency of K / B values at trace knock is line II.
Then, the distribution of the cumulative frequency of K / B values at light knock is line III.
Then, the distribution line IV of the cumulative frequency of K / B values during medium IV
Then, the distribution of the cumulative frequency of K / B values at heavy knock is line V
As shown in.

The distribution of the cumulative frequency of K / B values is an experimental result of the applicant, but is considered to be common to almost all engines.

Therefore, basically, the first reference value SL ₁ and the second reference value S
Set L ₂ to the value shown in Fig. 15, and set the first reference value.
The presence or absence of knocking is determined by SL ₁ , and the knocking generated by the _second reference value SL ₂ is small (minor).
Judging whether it is notting or big notting.

For example, the frequency of exceeding the second reference value SL ₂ is 2-3% at light knock, about 25% at medium knock, and about 70% at heavy knock, and the K / B value is the second.
When the reference value SL _{2 of} is exceeded, it can be determined that a large knock occurs by about 100% (97 to 98%).

By the way, the relationship between the power level of various knocks and the engine speed is, for example, as shown in FIG. 16, a solid line at non-knocks, a broken line at trace knocks, a one-dot chain line at light knocks, and a two-dot chain line at medium knocks. As shown.

As can be seen from FIG. 16, when the engine speed is in the high speed range, the human sensory evaluation is lowered due to the influence of the mechanical vibration of the engine itself, so that the knock allowable zone is widened.

Therefore, in this embodiment, as described above, the first reference value SL ₁ and the second reference value SL ₂ are changed according to the engine speed to realize highly efficient operation.

It is needless to say that the first reference value SL ₁ and the second reference value SL ₂ may both be fixed values or one of them may be fixed values.

Here, returning to FIG. 14, first, the meaning of the abbreviations will be described.

KFLG: Flag used to determine the presence or absence of knocking BCNT: A value indicating the number of ignitions from when the flag KFLG is reset (hereinafter referred to as "count value BCNT") KCNT: Ignition from the time the flag KFLG is set A value indicating the number of times (hereinafter referred to as "count value KCNT") ADVFBK: A value indicating the correction amount with respect to the reference value of the ignition angle (hereinafter referred to as "correction amount ADVFBK") Note that ignition is performed when the correction amount ADVFBK is incremented. The ignition timing is advanced when the timing is advanced and decremented.

Also, the value of these flags KFLG, each count value BCNT, KCN
The T and the correction amount ADVFBK are stored in the RAM 38 at a predetermined address allocated in advance.

Here, the processing in each STEP will be described. First, STEP
In step 10, the K / B value calculated by the process described above is compared with the _second reference value SL _2, and it is determined whether or not K / B value> SL _{2 and} whether or not a large knocking occurs. To determine.

At this time, if K / B value> SL _2, that is, if a large knock occurs, the process proceeds to STEP 27 described later.

On the other hand, if K / B value> SL _{2 is} not satisfied, that is, if K / B value ≦ SL ₂ and there is little knocking or no knocking, either K / B value is determined.
The B value is compared with the first reference value SL ₁ to determine whether K / B value> SL ₁ .

At this time, if K / B value> SL _1, that is, if a small (minor) knock has occurred, the process proceeds to STEP 22 described later.

On the other hand, if K / B value> SL _{1 is} not satisfied, that is, K / B value ≦ SL ₁ and no knocking occurs, STE
In STEP26, which will be described later in P12, it is determined whether or not the flag KFLG set (set to "1") when a knocking occurs is "0".

At this time, if the flag KFLG is "0", that is, if knocking does not occur, ignition is performed when K / B value ≤ SL ₁ continues for 28 cycles or more from the time knocking occurs in STEP 13 to 16. The process of advancing the time once is performed.

In other words, in STEP13 the count value BCNT is incremented (+
After 1), it is determined in STEP 14 whether or not the count value BCNT exceeds "28"(BCNT> 28).

At this time, if it is not BCNT> 28, the processing is terminated as it is, and if BCNT> 28, the correction amount ADVF of the ignition timing is set in STEP15.
BK is incremented (+1) to advance the ignition timing by 1 degree, and then the count value BCNT is cleared in STEP16 (BCNT = 0)
Then, the process ends.

On the other hand, if the flag KFLG is not "0", that is, if knocking has occurred in the past, 28 cycles or more from the time when K / B value> SL ₁ is reached in STEPs 17 to 21 K / B value ≤ S
When the state of L ₁ continues, processing for non-locking is performed.

In other words, in STEP 17, the count value KCNT is incremented (+
After 1), it is determined in STEP18 whether the count value KCNT exceeds "28"(KCNT> 28).

At this time, if KCNE> 28 is not satisfied, the processing is terminated as it is. If KCNT> 28, the flag KFLG is reset at STEP19 and then the count value KCNT is cleared at STEP20 (KCNT =
0), the count value BCNT is cleared in STEP21, and the process ends.

On the other hand, when K / B value> SL ₁ is reached in STEP 11, that is, when a small (minor) knock occurs, STEP
At 22, it is checked whether or not the flag KFLG is "0" to determine whether or not the first knocking has occurred.

At this time, if the flag KFLG is "0", that is, if it is the first knocking, the flag KFLG is set (KFLG = 1) in STEP23, and then the count value KCNT is cleared in STEP24 to end the processing.

On the other hand, if the flag KFLG is not “0”, that is, if the second or subsequent knocking occurs, whether or not the number of past ignitions is within 14 times (KCNT ≦ 14) in STEP25, that is,
Determine whether K / B value> SL ₁ is reached within 14 cycles.

At this time, if KCNT ≦ 14 is not satisfied, the above-mentioned STEP23 and 24 are executed to end the processing, and if KCNT ≦ 14, STEP26 is performed.
Then, the correction amount ADVFBK is decremented (-1) to retard the ignition timing by one degree, and then the above-mentioned STEP24 is executed to end the processing.

Note that the ignition timing is retarded when the K / B value> SL ₁ is reached within 14 cycles, that is, when the next knock occurs within 14 cycles after the knock occurs. As you can see from Fig.15, 7/10 at the time of trace knock
Since the K / B value exceeds the first reference value SL ₁ at a rate of 0, stochastically 100 / 7≈14, that is, once every 14 times, this condition (K / B value> SL ₁ ) It is based on what will happen.

Therefore, in the same way, this value is 100 /
16 ≒ 6 (times), 100/25 = 4 in case of medium notch
By setting (times), the engine can be controlled to a desired knock level. This was confirmed by an experiment by the applicant.

Thus, here, when a small knock occurs, the frequency of occurrence of the small knock is determined, and the correction amount of the ignition timing is determined based on the determination result of this frequency.

In this case, the retard amount of the ignition timing is set to 1 degree here, but it can be set to other values such as 1/4 degree and 1/2 degree.

Moreover, not only based on the frequency of occurrence of small knocks, but also the amount of retardation can be determined according to the strength of small knocks, that is, the magnitude of the K / B value. It is possible to suppress knocking without impairing performance and the like.

On the other hand, when K / B value> SL ₂ in STEP10, that is, when a large knock occurs, the amount of retard angle A is calculated in STEP27 and A = α (K / B value-SL ₂ ) is calculated. And calculate. Note that α is a constant preset for each engine or each operating condition, and a value corresponding to the engine or operating condition is read out by table lookup.

Then, in STEP 28, the correction amount ADVFBK is retarded by the retard amount A.

That is, as shown in FIG. 21, when a large knock that exceeds the second reference value SL ₂ occurs, the angle amount is increased according to the degree of knocking (strength), that is, the K / B value increases. .

Regarding the correction amount ADVFBK in each of STEP15, 26, 28 above, limit the value of the correction amount ADVFBK by judging whether the corrected correction amount ADVFBK does not exceed a predetermined value. Thus, it is possible to prevent the ignition timing from advancing or retarding more than a predetermined value.

As described above, in the control device for the internal combustion engine, the seventeenth
As shown in the figure, when K / B value ≤ SL ₁ (no knock),
When the predetermined condition is satisfied, the ignition timing correction amount is advanced by a predetermined angle, and when SL ₁ <K / B value ≤ SL ₂ (small knock), the ignition timing correction is performed when the predetermined frequency is reached. The amount is retarded by a predetermined angle (1 degree), and when K / B value> SL ₂ (large knock), the correction amount for retarding the ignition timing correction amount by a predetermined angle (A degree) is immediately determined.

Then, for example, the ignition timing is controlled by a program which is entered when the reference signal S ₂ from the crank angle sensor 13 is input and which performs a process as shown in FIG.

That is, in STEPs 31 to 33, the basic ignition timing AD according to the intake air amount and the engine speed is determined.

Note that this is performed by a characteristic value table backup stored in the ROM 37, for example, as shown in FIG.

Then, based on the determined basic ignition timing AD and the correction amount ADVFBK determined by the above-described processing, {70− (AD
+ ADVFBK)} to convert BTDC (AD + ADVFBK) into an angle from the input timing of the reference signal S ₂ , and the result of this calculation is set in the advance angle value (ADV) register of the I / O 39.

Further, in STEP34 to 36, the basic dwell angle DW is determined based on the determined ignition timing, and (DW + ADVFBK) is calculated based on the basic dwell angle DW and the above-mentioned correction amount ADVFBK, and this calculation result is calculated. The dwell angle (D
WELL) register.

In this way, the determined correction amount of the ignition timing is reflected in the ignition timing and the dwell angle to suppress the knocking.

As described above, in the control device for the internal combustion engine, the correction amount of the ignition timing is determined based on the occurrence frequency of the small knocking, while the correction amount of the ignition timing is determined based on the occurrence of the large knock. I have decided.

As a result, knocking can be suppressed and the operating efficiency of the engine can be improved.

That is, by setting the first comparison reference value SL ₁ as shown in FIG. 15, it is possible to detect a knock more than the light knock with high accuracy, but at this time, even if there is no problem, it is 10%. The degree exceeds the first comparison reference value SL ₁ .

At this time, if the retard control is performed every time when the reference value SL ₁ is exceeded as in the conventional case, the timing may be retarded even when the trace knock does not cause a problem, and the operating efficiency is deteriorated.

On the other hand, by controlling the ignition timing according to the frequency of the knocks exceeding the reference value SL ₁ as in the present invention, it is possible to detect the knocks more than the light knocks with high accuracy while ignoring the trace knocks without any problem. become able to.

By the way, when controlling the ignition timing according to the frequency of occurrence of such a small knock, if the retard amount (correction amount) is determined corresponding to the large knock, the engine is always operated on the retard side and the trace Since the goal of controlling the ignition timing in the vicinity of the knock state and avoiding the deterioration of the operating efficiency as much as possible cannot be achieved, a value corresponding to a small knock must be determined.

However, under such control, when a large knock occurs from the beginning, such as during rapid acceleration, knocking occurs in a continuous cycle, causing a so-called transient state that is very uncomfortable in hearing, There is a risk that sufficient acceleration performance may not be obtained.

Therefore, in the control device for the internal combustion engine, when a large knock occurs, the ignition timing is immediately retarded by a large predetermined retard amount.

As a result, it is possible to effectively suppress the occurrence of knocking during a transition such as during sudden acceleration, without impairing drivability.

Moreover, since the predetermined retard angle amount A is set to an optimum value according to the knocking strength, as described above, it is possible to perform control with good responsiveness and high accuracy.

FIG. 20 is a flow chart showing the knocking determination / correction amount determination processing executed by the main control circuit in another embodiment of the present invention.

In this embodiment, first, in STEP 61, STEP 1 to STEP 1 in FIG.
The same process as in 8 is performed to calculate the K / B value.

Then, in STEP 62, it is checked whether or not K / B value> SL _{1, and} it is determined whether or not knocking has occurred.

At this time, if K / B value> SL _{1 is} not satisfied, that is, if no knocking has occurred, in STEP 63 to 72, STEP 12 to STEP 12 in FIG.
Perform the same process as 21. The description is omitted.

On the other hand, if K / B value> SL ₁ , that is, if knocking has occurred, it is determined in STEP 73 whether the flag KFLG is “0”.

At this time, if the flag KFLG is "0", that is, if it is the first knocking, the current K / B value is stored as a K / B 'value in a predetermined address of RAM in STEP74 (this address is "K / B-OLD ").

Then, in step 75, set the flag KFLG, and in step 76
The counter value KCNT is cleared with and the processing ends.

On the other hand, if the flag KFLG is not "0", that is, if it is the second or subsequent knocking, it is determined in STEP77 whether or not the count value KCNT≤14 (see STEP25 in FIG. 14).

At this time, if KCNT ≦ 14 is not satisfied, STEP76 is executed and the process ends.

On the other hand, if KCNT ≤ 14
Based on the value and the previous K / B value (K / B 'value) stored in the RAM address K / B-OLD, the value KB ₁ is calculated as KB ₁ = (K / B + K / B') / 2 And calculate.

Then, in STEP 79, it is checked whether or not the value KB ₁ exceeds the second reference value SL ₂ (KB ₁ > SL ₂ ) and it is determined whether or not a large knock has occurred.

At this time, if KB ₁ > SL ₂ , that is, if it is a large knock, the amount of retard angle A is calculated in STEP 80 by calculating A = α (KB ₁ −SL ₂ ). Note that α is a constant preset for each engine or each operating condition, and a value corresponding to the engine or the operating condition is read out by a table lookup.

Then, in STEP 81, the correction amount ADVFBK is decremented (-A) by the retard amount A to retard the ignition timing by A degrees.

On the other hand, if KB ₁ > SL _{2 is} not satisfied, that is, if it is a small knock, the correction amount ADVFBK is decremented (−1) in STEP82 to retard the ignition timing by one degree.

As described above, in this embodiment, when the knocking is detected, the level of the knocking is responded only to the level which is considered to be a large knock, which is larger than the second reference value SL ₂ . Determine the correction amount.

As a result, it is possible to effectively suppress knocking, and it is possible to increase combustion efficiency to the maximum, without reacting hypersensitivity to a rare large-scale knock that rarely occurs. Performance and power performance can be improved.

In each of the above embodiments, the cylinder pressure sensor is provided on the ignition plug, but a so-called vibration sensor may be provided on the cylinder block.

〔The invention's effect〕

As described above, according to the present invention, by determining the occurrence frequency of small knocking with the minimum occurrence of knocking and correcting the ignition timing, a trace knock level that is advantageous in engine output and has no audible problem can be obtained. It is possible to improve the drivability by controlling the ignition timing.On the other hand, when a large knocking occurs, the ignition timing is immediately corrected with high accuracy by the correction amount set as a value proportional to the deviation from the reference value. It can prevent the deterioration.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing the configuration of the present invention, FIG. 2 is a schematic configuration diagram of a control device for an internal combustion engine embodying the present invention, and FIG. 3 shows an example of the control unit of FIG. Block diagrams, FIG. 4 is a functional block diagram of essential parts of the control unit, FIG. 5 is a sectional view and a plan view showing an example of a cylinder pressure sensor, and FIG. 6 is an example of a charge amplifier. Circuit diagram, FIG. 7 is a block diagram showing an example of a non-knock vibration energy detection circuit and an example of a knock vibration energy detection circuit, and FIG. 8 is a circuit diagram showing an example of the integrator of FIG. FIG. 10, FIG. 10 and FIG. 11 are waveform diagrams for explaining the principle of knocking detection in this embodiment, and FIG. 12 is for explaining the operation of the non-knock vibration energy detection circuit and the knock vibration energy detection circuit. Iminguchiyato view, Figure 13 and Figure 14 is a flowchart showing an example of Notsukingu determination and correction amount determination processing by the main control circuit executes, FIG. 15, in each Notsuku phenomenon for explaining FIG. 13
Explanatory diagram showing an example of the cumulative occurrence frequency of K / B value, FIG. 16 is an explanatory diagram showing an example of the relationship between the power level and the engine speed in each knock phenomenon, and FIG. 17 is that of FIG. Explanatory diagram showing the relationship between the K / B value and the correction amount of the ignition timing provided for the explanation, FIG. 18 is a flow chart showing an example of the ignition control process executed by the main control circuit, FIG. 19 is a diagram of FIG. FIG. 20 is a diagram showing an example of engine speed / intake air flow rate-advance value characteristics for explaining the basic ignition timing calculation process, and FIG. 20 is an example of a knocking determination / correction amount determination process in another embodiment of the present invention. Fig. 21 is an explanatory diagram showing the relationship between the K / B value and the correction amount of the ignition timing, which is also used for the explanation, 11 …… Control unit 13 …… Crank angle sensor, 21 …… Cylinder pressure Sensor 33 …… Vibration energy detection circuit when not knocked 34 …… Vibration energy detection when knocked Road 35 ...... main control circuit, 40 ...... ignition device

Claims (3)

[Claims] 1. A control device for an internal combustion engine that controls ignition timing based on a detection result of knocking of the internal combustion engine, and combustion pressure vibration detection means for detecting combustion pressure vibration of the internal combustion engine and the combustion pressure vibration detection means. The first determination means for determining whether or not a small knocking has occurred based on the detection result of (1), and an occurrence interval until the small knocking occurs based on the determination result of the first determination means. Second occurrence frequency determining means for determining the occurrence frequency of knocking by comparing with a frequency determination value, and second determination for determining whether or not a large knocking of a reference value or more has occurred based on the detection result of the combustion pressure oscillation detecting means. And the first correction for determining the correction amount of the ignition timing so that the occurrence frequency at the time of the trace knock is based on the detection result of the determination means and the frequency generation means. An amount determining means, a second correcting amount determining means for determining a correction amount of the ignition timing as a value proportional to the deviation from the reference value based on the determination result of the second determining means; 2. A control device for an internal combustion engine, comprising: ignition timing control means for controlling the ignition timing based on the determination result of the correction amount determination means of 2. 2. The control device for an internal combustion engine according to claim 1, wherein the first correction amount determining means includes means for determining a correction amount according to the degree of knocking that has occurred. 3. A combustion pressure vibration detecting means calculates a ratio or a difference between a vibration energy correlation value when not knocking and a vibration energy correlation value when knocking and outputs the calculation result as a detection result. The control device for an internal combustion engine according to claim 1 or 2.