JPH0692788B2 - Control device for internal combustion engine - Google Patents

Description

The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for controlling ignition timing.

[Conventional technology]

Conventionally, as an ignition timing control device for controlling the ignition timing of an internal combustion engine, for example, an in-cylinder pressure sensor (combustion pressure vibration sensor) for detecting an in-cylinder pressure of the engine is provided for each cylinder, and a knocking vibration frequency is detected from a detection signal of the in-cylinder pressure sensor. There is one that separates and extracts the signal component of the band, integrates the extracted signal in the explosion stroke of the internal combustion engine, and corrects and controls the ignition timing so that this integrated value becomes a predetermined target value (Japanese Patent Laid-Open No. 59-59). -114431 gazette).

That is, in the engine, the vibration component in the knocking vibration frequency band in the explosion stroke increases due to the occurrence of knocking, and the stronger the knocking strength, the more violent the vibration.

Therefore, the components in the knocking vibration frequency band are separated and extracted from the cylinder internal pressure of the engine, integrated in the explosion stroke to detect the integrated value corresponding to the knocking intensity, and the frequency at which this integrated value exceeds a predetermined target value is constant. Therefore, the ignition timing is controlled so as to avoid knocking without reducing the output of the internal combustion engine.

[Problems that the invention is trying to solve]

However, in such a control device for an internal combustion engine, the ignition timing is controlled only based on the integrated value in the explosion stroke.

Therefore, when the integrator malfunctions or when abnormal vibration occurs in the compression stroke part of the detection result of the in-cylinder pressure sensor, the integrated value becomes an abnormal value, and ignition timing control based on it may become inadequate.

For example, the ignition timing is retarded from the regular ignition timing to reduce the generated torque, the fuel consumption is lowered, the exhaust temperature is excessively increased, and the ignition timing is advanced from the regular ignition timing to cause knocking. Occurs. In particular, heavy knocks caused by the ignition timing being advanced too much may lead to engine damage in the worst case.

[Means for solving problems]

Therefore, the control device for an internal combustion engine according to the present invention is a control device for an internal combustion engine that controls ignition timing based on a detection result of combustion pressure vibration of the internal combustion engine, as shown in FIG. Combustion pressure oscillation detection means A, a storage means B that stores the maximum value of the combustion pressure or a crank angle of the maximum value based on the detection result of the combustion pressure oscillation detection means A, and the combustion pressure oscillation detection means. The determination means C for determining whether the ignition timing control is normal based on the comparison of the detected values after the top dead center of the non-idle operation and the idle operation of A, and the determination means C determined to be abnormal. Occasionally, ignition timing control means D for controlling the ignition timing based on the stored value of the storage means B is provided.

[Work]

When the ignition timing control based on the detection result of the combustion pressure oscillation becomes abnormal, the ignition timing control based on the stored maximum value of the combustion pressure or the crank angle of the maximum value can be performed.

In particular, in the present invention, the detected value of the combustion pressure oscillation after the top dead center where the combustion pressure oscillation is maximum during non-idle operation and the detected value after the top dead center during idle operation that does not cause abnormal combustion such as knocking. Since the abnormality is determined based on the comparison with, it is possible to eliminate the influence of noise due to the influence of various vibrations or the like that the internal combustion engine normally emits, and perform highly accurate abnormality determination and ignition timing control.

〔Example〕

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

FIG. 2 is a block diagram showing the configuration of a control device for a four-cylinder internal combustion engine embodying the present invention.

The in-cylinder pressure sensor 1A of the first cylinder is a piezoelectric conversion type pressure sensor, and is attached as a washer of an ignition plug 22A attached to a cylinder head 21A as shown in FIGS. The charge signal S ₁₁ corresponding to the cylinder internal pressure (cylinder internal pressure) is output.

The in-cylinder pressure sensors 1B to 1D of the second cylinder to the fourth cylinder are attached in the same manner as the in-cylinder pressure sensor 1A, and
The charge signals S _{12 to} S ₁₄ corresponding to the in-cylinder pressures of the fourth cylinder are output.

Chiyajianpu 2A amplifies after converting into a charge signal S ₁₁ from the first cylinder for in-cylinder pressure sensor. 1A, the output as the detection signal S _21.

As for the charge amplifiers 2B to 2D, the charge signals S from the in-cylinder pressure sensors 1B to 1D are the same as the charge amplifiers 2A.
_{12 to} S ₁₄ are converted into voltage signals and then amplified to detect signals S ₂₂
~ Output as S ₂₄ .

That is, the in-cylinder pressure sensors 1A to 1D and the charge amplifiers 2A to 2D constitute the combustion pressure vibration detecting means A of FIG.

The crank angle sensor 3 outputs the reference signal S ₂ at 70 ° before compression top dead center (BTDC) of each cylinder, and also outputs the position signal S ₃ every 1 or 2 degrees of the crank angle. The reference signal corresponding to the first cylinder in the reference signal S ₂ has a wider pulse width than the reference signals corresponding to the other cylinders.

The idle switch 4 detects whether the engine is in an idle state and outputs an idle state detection signal SI.

On the other hand, the control unit 5 has the storage means B,
The circuit also serves as the determination unit C and the ignition timing control unit D, and includes a multiplexer (MPX) 6, a signal processing circuit 7, a main control circuit 8 and the like.

The multiplexer 6 selects the detection signals S _{21 to} S ₂₄ from the charge amplifiers 2A to 2D that are input according to the selection signal from the main control circuit 8 and outputs them as the detection signal S ₂ n.

The signal processing circuit 7 detects the detection signal S ₂ from the multiplexer 6.
A predetermined signal processing is performed on n to convert it into a correlation value that correlates with the combustion pressure vibration energy when the engine is not knocked, a correlation value that correlates with combustion pressure vibration energy that the engine is knocked, and the like.

For example, as shown in FIG. 4, the signal processing circuit 7 uses a bandpass filter 7A to detect a detection signal S from a multiplexer 6 which is one of the detection signals S _{21 to} S ₂₄ from the charge amplifiers 2A to 2D. _{From 2} n, only the signal component of a predetermined frequency, that is, a frequency band (about 6 to 17 KHz) related to knocking is extracted.

Then, the detection signal (extraction signal) S ₄ output from the bandpass filter 7A is amplified by the amplification circuit 7B, and the amplified detection signal S ₅ is half-wave rectified by the rectification circuit 7C.

After that, the half-wave rectified detection signal S ₆ output from the rectifier circuit 7C is used as a set / reset signal from the main control circuit 8.
And by connexion integrated in integrator 7D controlled integral action in SSR, and outputs the integrated signal S ₇ indicating the integrated value of the correlation value correlating with the combustion pressure oscillation energy.

Returning to FIG. 2, the main control circuit 8 includes a CPU 10, a ROM 11 and a RAM 12
And a microcomputer including an I / O 13 having an A / D converter and the like built therein.

The main control circuit 8, the reference signal S ₂ and the position signal S ₃ from the crank angle sensor 3, and an idle state detection signal SI from the idle Sui Tutsi 4, the integrated signal from the signal processing circuit 7
Enter S ₇ etc.

The excisional based on the reference signal S ₂ and the position signal S ₃ from the crank angle sensor 3 to the integrator 7D of the signal processing circuit 7 /
It outputs the reset signal SSR and controls its integration operation.

In addition, here, the main control circuit 8 is 40 degrees before the compression top dead center (BT
The integration operation of the integrator 7D is started at DC40 °), the integration operation is stopped at the compression top dead center (TDC), and after the compression top dead center (ATD
C) Start integration again at 5 ° and stop integration at ATDC 45 °.

Further, the main control circuit 8 relates to the detection and storage of the crank angle corresponding to the maximum value of the combustion pressure, the abnormality determination of the ignition timing control, and the knocking based on the above-mentioned signals and various input signals such as an intake air amount signal (not shown). Processing related to ignition timing control such as determination, determination of ignition timing correction amount, and determination of ignition timing is performed.

Then, based on the determined ignition timing, the power transistor 16 of the ignition device 15 is turned on / off to control the ignition timing.

The control of the ignition timing (ON / OFF control of the power transistor 16) corresponds to the ignition timing determined by the advance value (ADV) register and the dwell angle (DWELL) register (not shown) provided inside the I / O 13. The values (advance value, dwell angle) are 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 16 is turned on or off. To do.

Further, in the ignition device 15, the power transistor 16 is controlled to be turned on / off, whereby the primary current of the ignition coil 18 supplied from the battery 17 is interrupted and a high voltage is applied to the secondary side thereof. This high voltage is generated by the distributor 19 and the spark plugs of the first cylinder to the fourth cylinder are generated.
20A to 20D are selectively distributed and applied to generate spark discharge and ignite.

The main control circuit 8 performs controls other than the control relating to the ignition timing, but the description thereof will be omitted.

Next, the operation of this embodiment thus configured will be described with reference to FIG. 5 and subsequent figures.

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

Generally, it is considered that the determination of the knock level by the human hearing is made by the relative strength difference between the sound pressure level due to the background noise that is constantly generated and the sound pressure level due to the knocking vibration. .

Therefore, if the vibration energy of the in-cylinder pressure (combustion pressure vibration energy) at the time of non-knocking and the vibration energy of the in-cylinder pressure at the time of notting are directly compared, it is possible to detect a knocking level that is in good agreement with human sensory evaluation. It will be possible.

By the way, empirically, it can be considered that knocking does not occur before top dead center, so the integrated value obtained by (rectifying) integrating the detected value of in-cylinder pressure oscillation (combustion pressure oscillation) before top dead center is Whether or not there is a knocking after the dead point,
It can be said that it is a 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, it is possible to directly compare the vibration energy of the in-cylinder pressure during non-knocking with the vibration energy of the in-cylinder pressure during the combustion stroke.

In this case, the integration section must be selected so as not to be affected by the vibration of the spark plug caused by the vibration of the seating / seating of the intake / exhaust valve. TDC and ATDC 5 ° ~ ATDC 45 ° are selected.

Next, control of the integration operation of the integrator 7D of the signal processing circuit 7 by the main control circuit 8 for performing such processing will be described with reference to FIG.

First, in the 4-cylinder internal combustion engine, the first cylinder # 1 to the fourth cylinder
Ignition of cylinder # 4 is controlled in the order of # 1 → # 3 → # 4 → # 2 → # 1.

At this time, the crank angle sensor 3 outputs the reference signal S _{2 at} 70 ° before the top dead center (TDC) of each cylinder as shown in FIG. The position signal S ₃ is output every 1 ° (or 2 °) of the crank angle. In addition,
As described above, the pulse width of the reference signal S ₂ for the first cylinder is wider than the pulse width of the reference signal S ₂ for the other cylinders.

On the other hand, when the in-cylinder pressure sensors 1A to 1D and the charge amplifiers 2A to 2D are normal, the charge amplifier 2A outputs the same figure (C).
The detection signal S ₂₁ as shown in FIG. 2 is output, and the similar detection signals S _{22 to} S ₂₄ are also output from the other charge amplifiers 2B to 2D. Therefore, the multiplexer 6 detects the detection signal S 2 to S ₂₄ shown in FIG. The signal S ₂ n is output.

Accordingly, the detection signal S ₂ from the multiplexer 6
When only the signal of a predetermined frequency is extracted from n by the band pass filter 7A of the signal processing circuit 7 and amplified by the amplification circuit 7B, the detection signal S ₅ shown in FIG. Is output, and the detection signal S ₆ as shown in (f) of the figure is input to the integrator 7D by rectifying this by the rectifying circuit 7C.

Therefore, the main control circuit 8 starts the internal counter and starts counting the position signal S ₃ from the time when the reference signal S ₂ from the crank angle sensor 3 is input.

The main control circuit 8, in FIG. (H) are shown as example for the first cylinder BTDC40 ° Natsuta time t _1, the integral operation of the integrator 7D to "H" excisional / reset signal SSR Start / set signal S at time t ₂ when TDC
Set SR to "L" to stop the integration operation.

After that, at the time t ₃ when ATDC reaches 5 °, integrator 7D is similarly operated.
The integration operation of is started, and the integration operation is stopped at time t ₄ when the temperature reaches ATDC 45 °.

Accordingly, the integrated signal S ₇ output from the integrator 7D is
For example, as shown in the same figure (g) between time points t _{1 and} t ₄ , the correlation value (integral value) correlated with the vibration energy at the time of non-knock is shown by the integration operation between time points t _{1 and} t ₂ . Obtained, time t ₃
A correlation value (integral value) that correlates with the vibration energy at the time of knocking can be obtained by the integration operation from to t ₄ .

The main control circuit 8, and controls the integrating operation of the integrator 7D in the same timing for the second cylinder to the fourth cylinder, the drawing as a whole integrated signal S ₇ output from the integrator 7D (DOO ).

Therefore, the main control circuit 8 is
The integrated signal S ₇ in TDC is A / D converted, and this A / D converted value is used as the amount B correlated with the vibration energy in the non-knock state in RAM 1
Stored at a predetermined address of 2.

Also, the integrated signal S ₇ at each ATDC 45 ° is A / D converted,
This A / D converted value is stored in a predetermined address of the RAM 12 as a quantity K correlated with the vibration energy at the time of knocking.

Regarding the knocking control, the ratio between the amount B and the amount K (K / B) or the ratio between the average value of the amount K and the amount K (K /)
Is calculated and used.

Next, the relationship between the ignition timing, the knocking strength, and the crank angle θpmax that maximizes the cylinder pressure will be described.

Generally, the relationship between the ignition timing, the knocking strength, and the crank angle θpmax that maximizes the in-cylinder pressure is as shown in FIG. The characteristic shown in FIG. 6 is the result of an experiment at a full load of 2400 RPM in a 4-cylinder engine.

That is, the ignition timing and the knocking strength have a good correlation as long as the operating conditions are determined, and the crank angle θpmax that maximizes the ignition timing and the in-cylinder pressure also have a good correlation.

From these things, the knocking strength and the crank angle θpm
There is a good correlation with ax if the operating conditions are determined. For example, in the example shown in FIG. 6, in order to control the trace knock, the ignition timing may be controlled so that θpmax becomes 13 ° ATDC.

Therefore, when the ignition timing control based on the detection result of the combustion pressure oscillation, that is, the detection result of the in-cylinder pressure (hereinafter also referred to as “normal ignition timing control”) is normal, the θpmax value is learned according to the operating condition. When an abnormality occurs in the normal ignition timing control system, the ignition timing is controlled so that the crank angle θpmax at which the cylinder pressure becomes maximum becomes the stored θpmax value according to the operating conditions. By doing so, it is possible to avoid the inconvenience caused by the abnormality of the normal ignition timing control system.

Next, the detection of the crank angle θpmax that maximizes the cylinder pressure will be described.

The detection signal S ₂ n from the multiplexer 6 as shown in FIG. 5D is input to the I / O 13 of the main control circuit 8.

Therefore, the main control circuit 8 is, for example, ATDC40 from ATDC2 °.
Up to 2 °, the detection signal S ₂ n from the multiplexer 6 is set to 2
A / D conversion is performed for each degree.

After that, these A / D converted values are compared, and the crank angle corresponding to the largest value is calculated as the crank angle θpmax.
Is stored in the RAM 12 at a predetermined address.

Then, when the normal ignition timing control performed based on the integrated signal S ₇ from the signal processing circuit 7 is normal, learns crank angle θpmax to each operating condition, the RAM12 the learning value of the θpmax as "Lθpmax" Store and store at a predetermined address. The operating condition is determined by, for example, a combination of the engine speed and the intake air amount.

Here, describing how to obtain Lθpmax, θpmax at the time of normal ignition timing control may be used as it is as Lθpmax, or in order to obtain more stable Lθpmax, θ
The moving average value of pmax is Lθpmax = (1−β) Lθpmax + βθpmax However, the value calculated by the calculation of (0 <β <1) may be set as Lθpmax.

Next, the principle of abnormality determination of the normal ignition timing control system that controls the ignition timing based on the integrated signal S ₇ will be described.

Generally, the amount K corresponding to the vibration energy of the in-cylinder pressure during the combustion stroke has a minimum value when the internal combustion engine is in idle operation,
Under any other operating conditions, the quantity K cannot be smaller than the quantity K during idle operation.

FIG. 7 shows the result of measuring the amount K for each operating condition of the four-cylinder internal combustion engine under the condition that knocking does not occur by the applicant, and according to various experiments, the relationship shown in FIG. Can be considered to hold in most engines.

Therefore, the value of the amount K during idle operation, that is, the minimum value of the amount K is stored in advance in a predetermined address of the RAM 12 as the minimum value KMIN, and the amount K and the minimum value KMIN under operating conditions other than during idle operation are stored. By comparing with, it is possible to determine that an abnormality has occurred in the ignition timing control system when K <KMIN.

Here, describing how to obtain the minimum value KMIN, the amount K during idle operation may be used as it is as the minimum value KMIN, or in order to obtain a more stable minimum value KMIN, the amount K during idle operation The moving average value of KMIN = (1−α) KMIN + αK However, the value calculated by the calculation of (0 <α <1) may be set as the minimum value KMIN.

Instead of the amount K which is the vibration energy correlation value at the time of knocking, the amount B which is the vibration energy correlation value at the time of non-knock detected before the top dead center is used instead of the amount K at the time of idling. Using the amount B as the minimum value BMIN, compare this with the amount B under operating conditions other than during idle operation and B <BM
It is also possible to determine that it is abnormal when it becomes IN. However, since the rise of the combustion pressure or the occurrence of knocking is remarkable after the top dead center, it is better to use the amount K after the top dead center as described above in order to eliminate the influence of noise due to vibration generated by the internal combustion engine or the like. This is desirable because it enables more accurate abnormality determination.

Next, details of the abnormality determination / ignition timing control executed by the main control circuit 8 will be described with reference to FIG.

Referring to FIG. 8, cylinder discrimination processing is performed in STEP1. This is because when the reference signal S ₂ from the crank angle sensor 3 is input (when it rises), the internal counter is activated to count the position signal S ₃ from the crank angle sensor 3 and
Whether or not it is the first cylinder is determined from the count value when S ₂ falls, and other cylinders are determined based on the determination result.

That is, as described above, the pulse width of the reference signal S ₂ output at 70 ° before the top dead center of the first cylinder is larger than that of the reference signal S ₂ output at 70 ° before the top dead center of the other cylinder. Is wide. For example, the pulse width of the reference signal S ₂ for the first cylinder with respect to the range of about 14 °, the pulse width of the reference signal S ₂ for the second cylinder to the fourth cylinder is ° 4 ° 5.

Therefore, by measuring the pulse width of the input reference signal S ₂ , if the count value is 10 ° or more, the first
Cylinder can be determined, and the reference signal S ₂ input thereafter is
Is the order of the third cylinder, the fourth cylinder, and the second cylinder, so that each cylinder can be identified.

Then, in STEP2, the multiplex drive 6 is driven, and the charge amplifier corresponding to the cylinder according to the cylinder discrimination result in STEP1.
Select one of the detection signals S _{21 to} S ₂₄ from 2A to 2D,
Output as detection signal S ₂ n.

Thereafter, in STEP 3, the integration timing of the integrator 7D of the signal processing circuit 7 is set as described above, and the integration operation of the integrator 7D is performed between BTDC 40 ° to TDC and ATDC 5 ° to 45 °.

Then, in STEP 4, an ignition timing correction amount determination process for determining an abnormality in the ignition timing control system and determining an ignition timing correction amount is performed.

FIG. 9 is a flow chart showing in detail the ignition timing correction amount determination processing in FIG.

First, the meanings of the abbreviations used in the figure (excluding those already described) will be described.

KMIN: Amount K during idle operation, that is, the minimum value.

α: A correction coefficient of the minimum value KMIN, which is a value satisfying 0 <α <1.

Lθpmax (N, Qa): Means the value of θpmax stored for each operating condition, and is stored in the table of the RAM 12 divided by the engine speed N and the intake air amount Qa.

β: A correction coefficient of Lθpmax (N, Qa), which is a value satisfying 0 <β <1.

dc: A correction amount of ignition timing. If dc is positive, it represents the advance side correction amount, and if it is negative, it shows the retard side correction amount.
That is, the ignition timing advances as the correction amount increases.

Next, the ignition timing correction amount determination processing will be described with reference to FIG.

In STEP 11, the detection signal S ₂ n from the multiplexer 6 is A / D converted every 2 ° from ATDC 2 ° to ATDC 40 °, and each A / D converted value and crank angle are temporarily stored in the data area of the RAM 12.

Further, the rectification integration signal S ₇ within a predetermined angle range of the detection signal S ₂ n
A / D is converted by TDC to obtain the quantity B, and ATDC 45 ° is A / D converted to obtain the quantity K.

Then, in STEP 12, the crank angle which is the maximum value among the A / D converted values every 2 ° temporarily stored in the RAM 12 in STEP 11 is obtained as θpmax.

After that, in STEP 13, the idle state detection signal SI from the idle switch 4 is checked to determine whether or not it is in the idle state.

At this time, if it is in the idle state, in STEP14, the minimum value KMIN corresponding to the idle amount K is rewritten.

That is, the moving average value of the amount K at idle is calculated by calculating (1−α) · KMIN + αK, and the calculated moving average value is stored as a new minimum value KMIN in a predetermined address of the RAM 12.

Then, in STEP 15, the ignition timing correction amount dc is set to "0" (dc
← 0). That is, in this embodiment, the basic ignition timing is controlled during idling.

On the other hand, if STEP13 is not idle, STEP16
The amount K is compared with the minimum value KMIN corresponding to the amount K at the time of idling to determine whether K ≧ KMIN.

At this time, if K ≧ KMIN, that is, if the normal ignition timing control system that controls the ignition timing based on the integrated value of the detection result of the in-cylinder pressure is normal, at STEP 17, θpmax for each normal operating condition is set. The corresponding Lθpmax (N, Qa) is learned and rewritten.

That is, the moving average value of θpmax at the normal time is stored in a predetermined address of the RAM 12 as a new Lθpmax (N, Qa) by calculating the value of (1-β) Lθpmax (N, Qa) + βθpmax. .

Then, in STEP 18, the ignition timing correction amount dc is calculated based on the integrated output S ₇ from the signal processing circuit 7.

On the other hand, if K ≧ KMIN in STEP16, that is, if the normal ignition timing control system is abnormal, in STEP19, STEP17
The ignition timing correction amount dc is calculated based on θpmax according to the current operating condition stored in step.

Next, details of the ignition timing correction amount calculation processing (STEP 18) based on the integrated output in FIG. 9 will be described with reference to FIG.

First, the meaning of each abbreviation in the figure (excluding those already described) will be described.

SL: A reference value for determining the presence or absence of knocking.

KFLG: This flag is used to determine whether or not there is knocking.

BCNT: A value indicating the number of ignitions from the time the flag KFLG is reset (hereinafter referred to as "count value BCNT") KCNT: A value indicating the number of ignitions from the time the flag KFLG is set (hereinafter "count value KCNT" First, in STEP31, the ratio (K / B value) between the quantity B, which is the vibration energy correlation value at the time of non-knocking, and the quantity K, which is the vibration energy correlation value at the time of knocking, is calculated and the quantity is calculated. K / B calculation processing for normalizing the quantity K based on B is performed.

Instead of calculating the ratio between the amount B and the amount K, the ratio (K /) between the average value of the amount K and the amount K may be calculated and normalized.

Then, in STEP32, the K / B value calculated by the above-described processing is compared with the reference value SL to determine whether K / B value> SL,
It is determined whether knotting has occurred.

At this time, if K / B value> SL, that is, if a knock has occurred, the process proceeds to STEP 43 described later.

On the other hand, if K / B value> SL, that is, K / B value ≤
If SL and no knocking occurs, STEP33
In step 44, which will be described later, it is determined whether or not a flag KFLG set (set to "1") when a knocking occurs is "0".

At this time, if the flag KFLG is "0", that is, if the knocking has not occurred, the ignition timing is set when the K / B value ≤ SL continues for 20 cycles or more from the time when the knocking occurs in STEP34 to 37. Is advanced once.

In other words, in STEP34, the count value BCNT is incremented (+
After 1), it is determined in STEP35 whether or not the count value BCNT exceeds "20"(BCNT> 20).

At this time, if BCNT> 20, the process is terminated as it is. If BCNT> 20, STEP36 increments the ignition timing correction amount dc (+1) to advance the ignition timing once, and then STEP37. Then, the count value BCNT is cleared (BCNT = 0) and the processing is ended.

On the other hand, if the flag KFLG is not "0", that is, if knocking has occurred in the past, K / B value> SL in STEP 38 to 42, K / B value ≤SL for 20 cycles or more
When the state of is continued, the processing for non-locking is performed.

In other words, in step 38, increment the count value KCNT (+
After 1), it is determined in STEP39 whether the count value KCNT exceeds "20"(KCNT> 20).

At this time, if KCNT> 20, the process is terminated as it is. If KCNT> 20, STEP40 resets the flag KFLG and then STEP41 clears the count value KCNT (KCNT =
0), the count value BCNT is cleared in STEP 42, and the processing is ended.

On the other hand, when K / B value> SL in STEP42, that is, when a knock occurs, in STEP43, check whether the flag KFLG is "0" to determine whether the first knocking occurs. To do.

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 STEP44, and then the count value KCNT is cleared in STEP45 and the processing is ended.

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 10 (KCNT ≦ 10) in STEP46, that is,
Determine if K / B value> SL within 10 cycles.

At this time, if KCNT ≦ 10 is not satisfied, the above-mentioned STEP45 is executed to end the processing, and if KCNT ≦ 10, STEP47 decrements (-1) the ignition timing correction amount dc to set the ignition timing to 1 After retarding the angle, the above-mentioned STEP 45 is executed and the processing is ended.

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

Regarding the correction amount dc in each of the above STEPs 36 and 47,
By determining whether or not the corrected correction amount dc does not exceed a predetermined value, and limiting the value of the correction amount dc, the ignition timing does not advance or retard beyond a predetermined value. You can also do so.

Also, the amount of retard angle decremented in STEP 47 is 1/2 degree, 1/4
The degree is not limited to one degree, and may be a value according to the magnitude of the K / B value, that is, the strength or degree of the knock.

Next, the ignition timing correction amount calculation processing (STEP 19) based on θpmax in FIG. 9 will be described with reference to FIG.

First, at STEP 51, the crank angle θpm at which the cylinder pressure becomes maximum
By comparing ax with the θpmax value learned and stored for each operating condition when the ignition timing control system based on the integrated output S ₇ is normal, that is, Lpmax (N, Qa), θpmax = Lθpmax
It is determined whether or not (N, Qa).

At this time, if θpmax = Lθpmax (N, Qa), it is considered that the control is performed at the target ignition timing, and the ignition timing is maintained as it is.

On the other hand, if θpmax = Lθpmax (N, Qa) is not satisfied,
At STEP 52, it is determined whether or not θpmax> Lθpmax (N, Qa).

At this time, if θpmax> Lθpmax (N, Qa), it means that the ignition timing is retarded too much, so in STEP53, add “0.1 °” to the ignition timing correction amount dc (dc + 0.1 °). To advance.

If θpmax> Lθpmax (N, Qa) is not satisfied, the ignition timing has advanced too much. Therefore, in STEP54, "0.1 °" is subtracted from the ignition timing correction amount dc (dc-0.1 °). Retard.

Next, the ignition timing control process will be described with reference to FIG.

This process is performed by, for example, a reference signal from the crank angle sensor 3.
When S ₂ is input, it is entered and execution starts.

First, in STEP61, the basic ignition timing D is determined according to the intake air amount, the engine speed, and the like. This is done by a table-up of characteristic values stored in the ROM 11 as shown in FIG. 13, for example.

Then, based on the basic ignition timing D determined in STEP 62 and the ignition timing correction amount dc determined by the above-described processing, {70- (D + dc)} is calculated, and BTDC (D + dc)
Is converted to an angle from the input timing of the reference signal S ₂ , and ST
In EP63, the result of this operation is set in the advance angle value (ADV) register of I / O13.

As described above, the control device for the internal combustion engine stores the crank angle θpmax at which the combustion pressure reaches the maximum value based on the detection result of the combustion pressure oscillation of the engine, and controls the ignition timing based on the detection result of the combustion pressure oscillation. Is determined, and the ignition timing is controlled based on the combustion pressure oscillation detection result and the stored θpmax and abnormality determination determination result.

Thereby, when the ignition timing control based on the detection result of the combustion pressure oscillation becomes abnormal, it becomes possible to control the ignition timing based on θpmax stored in advance for each operating condition.

Therefore, even when the ignition timing control based on the detection result of the combustion pressure oscillation becomes abnormal, it is possible to avoid inconveniences such as a decrease in generated torque, a decrease in fuel consumption, an increase in exhaust temperature, and the occurrence of knocking.

Next, an embodiment in which the maximum value Pmax in the combustion stroke of the combustion pressure is used instead of the crank angle θpmax in which the combustion pressure has the maximum value in the above-described embodiment will be described with reference to FIG. 14 and subsequent figures.

First, the relationship between the ignition timing, the knocking strength, and the maximum value Pmax of the in-cylinder pressure during the explosion stroke will be described.

Generally, the relationship between the ignition timing, the knocking strength, and the maximum value Pmax of the in-cylinder pressure during the explosion stroke is as shown in FIG. The characteristics shown in FIG. 14 are the experimental results at a full load of 2400 RPM in a 4-cylinder engine.

That is, the ignition timing and the knocking intensity have a good correlation as long as the operating condition is determined, and the ignition timing and the maximum value Pmax of the in-cylinder pressure also have a good correlation.

From these things, the knocking intensity and Pmax have a good correlation as long as the operating condition is determined. For example, in the example shown in FIG. 14, in order to control the trace knock, the ignition timing may be controlled so that Pmax becomes 2.9 V at the output of the charge amplifier.

Therefore, when the detection result of the combustion pressure oscillation, that is, the ignition timing control based on the detection result of the in-cylinder pressure is normal,
The Pmax value is learned and stored according to the operating condition, and when an abnormality occurs in the normal ignition timing control system, the ignition timing is controlled so that Pmax becomes the stored θpmax value according to the operating condition. By doing so, it is possible to avoid the inconvenience caused by the abnormality of the normal ignition timing control system.

Next, the detection of the maximum value Pmax of the in-cylinder pressure will be described.

The detection signal S ₂ n from the multiplexer 6 as shown in FIG. 5D is input to the I / O 13 of the main control circuit 8.

Therefore, the main control circuit 8 performs A / D conversion of the detection signal S ₂ n from the multiplexer 6 every 2 ° during the period from ATDC 2 ° to ATDC 40 °, for example.

After that, these A / D converted values are compared, and the largest value among them is stored as Pmax in a predetermined address of the RAM 12.

Then, RAM when normal ignition timing control performed based on the integrated signal S ₇ from the signal processing circuit 7 is normal, learns Pmax for each operating condition, the learned value of the Pmax as "LPmax"
Store and store in 12 predetermined addresses. The operating condition is determined by, for example, a combination of the engine speed and the intake air amount.

Here, describing how to obtain LPmax, Pmax at the time of normal ignition timing control may be used as LPmax as it is, or in order to obtain more stable LPmax, the moving average value of Pmax is calculated as LPmax = ( 1-γ) LPmax + βPmax However, the value calculated by calculating (0 <γ <1) may be set as LPmax.

Next, the ignition timing correction amount determination processing in FIG. 8 in this case will be described with reference to FIG.

First, in STEP111, the detection signal S ₂ n from the multiplexer 6 is sent.
A / D conversion is performed every 2 ° from ATDC2 ° to ATDC40 °, and each A / D converted value is temporarily stored in the data area of RAM12.

Further, the rectification integration signal S ₇ within a predetermined angle range of the detection signal S ₂ n
A / D is converted by TDC to obtain the quantity B, and ATDC 45 ° is A / D converted to obtain the quantity K.

Then, in STEP112, the maximum value among the A / D converted values for every 2 ° temporarily stored in the RAM12 in STEP111 is obtained as Pmax.

Then, in STEP113, the idle state detection signal SI from the idle switch 4 is checked to determine whether or not it is in the idle state.

At this time, in the idle state, in STEP114, the minimum value KMIN corresponding to the idle amount K is rewritten.

That is, the moving average value of the amount K at idle is calculated and stored as a new minimum value KMIN at a predetermined address of the RAM 12.

Then, in STEP115, the ignition timing correction amount dc is set to "0" (d
c ← 0), control is performed at the basic ignition timing.

On the other hand, if it is not idle in STEP113, STEP1
In step 16, the quantity K is compared with the minimum value KMINi corresponding to the quantity K during idling to determine whether K ≧ KMIN.

At this time, if K ≧ KMIN, that is, if the normal ignition timing control system that controls the ignition timing based on the integrated value of the detection result of the in-cylinder pressure is normal, STEP 117 sets Pmax for each normal operating condition. The corresponding LPmax (N, Qa) is learned and rewritten.

That is, the moving average value of Pmax under normal conditions is calculated as (1-γ) LPmax (N, Qa) + γPmax, and the calculated value is set as a new LPmax (N, Qa).
Store at the specified address of AM12.

After that, in STEP 118, the ignition timing correction amount dc is calculated based on the integrated output S ₇ from the signal processing circuit 7.

On the other hand, if K ≧ KMIN in STEP116, that is, if the normal ignition timing control system is abnormal, in STEP119 STE
The ignition timing correction amount dc is calculated based on Pmax corresponding to the current operating condition stored in P117.

Next, the ignition timing correction amount calculation processing (STEP 119) based on Pmax in FIG. 15 will be described with reference to FIG.

First, in STEP 151, the maximum value Pmax of the in-cylinder pressure during the explosion stroke
And the Pmax value learned and stored for each operating condition when the ignition timing control system based on the integrated output S ₇ is normal, that is,
By comparing with LPmax (N, Qa), it is determined whether or not Pmax = LPmax (N, Qa).

At this time, if Pmax = LPmax (N, Qa), it is considered that the control is performed at the target ignition timing, and the ignition timing is set as it is.

On the other hand, if Pmax = LPmax (N, Qa), then STEP1
At 52, it is determined whether or not Pmax <LPmax (N, Qa).

At this time, if Pmax <LPmax (N, Qa), it means that the ignition timing is retarded too much, so in STEP153, add "0.1 °" to the ignition timing correction amount dc (dc + 0.1 °). To advance.

If Pmax> LPmax (N, Qa), the ignition timing has advanced too much. Therefore, in STEP154, subtract "0.1 °" from the ignition timing correction amount dc (dc-0.1 °). Retard.

In this way, even if the maximum value Pmax of the in-cylinder pressure is stored, the same effect as in the above embodiment can be obtained.

In each of the above-described embodiments, an example in which all cylinders are controlled to have a uniform ignition timing has been described. However, in the case where the ignition timing is controlled for each cylinder or for each cylinder group having a plurality of cylinders as one group. The present invention can be similarly implemented.

〔The invention's effect〕

As described above, according to the present invention, the crank angle θpmax or the maximum value Pmax of the combustion pressure is stored based on the detection result of the combustion pressure oscillation of the engine, and the combustion pressure oscillation detection result is stored. It is determined whether the ignition timing control based on normal is normal, and if it is determined to be abnormal, θpmax or Pm
Since the ignition timing is controlled based on ax, when the ignition timing control based on the detection result of combustion pressure oscillation becomes abnormal, θpmax or Pm stored in advance for each operating condition is stored.
It becomes possible to control the ignition timing based on ax, and even when the ignition timing control based on the detection result of the combustion pressure oscillation becomes abnormal, the generated torque decreases, the fuel consumption decreases, the exhaust temperature rises, and the knocking occurs. Inconveniences such as occurrence can be avoided.

In particular, in the present invention, since the abnormality is determined by comparing the detected values of the combustion pressure oscillation after the top dead center during the non-idle operation and the idle operation, it is possible to prevent the erroneous determination of normality or failure. Therefore, it is possible to perform more accurate determination and ignition timing control.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing the configuration of the present invention, FIG. 2 is a block diagram showing the configuration of a control device for an internal combustion engine embodying the present invention, and FIG. 3 is a sectional view showing an example of a cylinder pressure sensor. A plan view, FIG. 4 is a block diagram showing an example of a signal processing circuit, FIG. 5 is a timing chart for explaining integration operation control processing of an integrator executed by the main control circuit, FIG. 6 is ignition timing, FIG. 7 is a characteristic diagram for explaining the relationship between the knock intensity and θpmax, FIG. 7 is a diagram showing the engine speed / intake air amount-quantity K characteristic for explaining the principle of the ignition timing control system abnormality determination, and FIG. FIG. 9 is a flow chart showing an example of abnormality determination / ignition timing correction amount determination processing executed by the control circuit, FIG. 9 is a flow chart showing an example of ignition timing correction amount determination processing of FIG. 8, and FIG. 10 is shown in FIG. Ignition timing correction amount calculation process based on rake integration value 11 is a flow chart showing an example of the ignition timing correction amount calculation processing based on θpmax in FIG. 9, and FIG. 12 is a flow chart showing an example of the ignition control processing executed by the main control circuit. FIG. 13 is a diagram showing an engine speed / intake air flow rate-advance value characteristic for explaining the basic ignition timing calculation process of FIG. 12, and FIG. 14 is an ignition timing in another embodiment of the present invention. A characteristic diagram for explaining the relationship between the knock intensity and Pmax, FIG. 15 is a flowchart showing an example of the ignition timing correction amount determination process, and FIG. 16 is a diagram showing the ignition timing correction amount calculation process based on Pmax in FIG. It is a flowchart which shows an example. 1A to 1D …… Cylinder pressure sensor 2A to 2D …… Charge amplifier 3 …… Crank angle sensor 4 …… Idle switch 5 …… Control unit, 7 …… Signal processing circuit 7C …… Rectifier, 7D …… Integrator 8… … Main control circuit, 15 …… Ignition device

Claims (1)

[Claims] 1. A control device for an internal combustion engine, which controls an ignition timing based on a detection result of combustion pressure oscillation of the internal combustion engine,
Combustion pressure oscillation detecting means for detecting combustion pressure oscillation of the engine, storage means for storing a maximum value of combustion pressure or a crank angle of the maximum value based on a detection result of the combustion pressure oscillation detecting means, and the combustion pressure Judgment means for judging whether or not the ignition timing control is normal based on the comparison of the detection values after the top dead center between the non-idle operation and the idle operation of the vibration detection means, and the judgment means has determined that the abnormality is An ignition timing control means for controlling the ignition timing on the basis of the stored value of the storage means.