JPS59201973A - Ignition timing control device in internal-combustion engine - Google Patents

Abstract

PURPOSE:To make it possible to precisely control the ignition timing even upon idling and as well low load operation, by providing such an arrangement that combustion pressure alone is separated from cylinder pressure and is detected so that the crank angle at which the combustion pressure comes to be maximum, is precisely detected. CONSTITUTION:Upon engine operation the pressure in each cylinder, which is obtained by processing the outputs of a crank angle sensor 1 and cylinder pressure sensors 2, before the top dead center during the compression stroke is stored in a memory means 3 at each predetermined crank angle positions. Then, a compressive pressure calculating means 4 calculates an objective waveform with respect the top dead center of the stored pressure waveform before the top dead center, and therefore, the compressive pressure at every predetermined crank angle position after the top dead center is calculated. Then, the output of the above-mentioned means 4 is subtracted from the output of the pressure sensor 2 at each predetermined crank angle positions so that combustion pressure at each predetermined angle positions after the top dead center is estimated, and thereafter, the crank angle theta at which combustion pressure becomes maximum, is obtained from the value obtained above, thereby the ignition timing is controlled so that the thus obtaind value thetam comes to a predetermined position after the top dead center.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an ignition timing control device for an internal combustion engine, and in particular, it divides cylinder pressure into compression pressure and combustion pressure, and determines the crank angle at which the combustion pressure is maximum. The present invention relates to a technique for controlling i to a predetermined value.

[Prior art]

Conventional ignition 111 period control technology includes, for example, 1. v Asaaki 45-74866 Shira, Unexamined Japanese Patent Publication No. 57-1 15
．． 3 (There are 1 shi J, etc., and as a prior art to the present invention, the present applicant has 1.? Asaaki 57 122200> No.
41: Asaaki 57-l 2! ] OO8 Shiji etc. have been applied for.

”The two prior art techniques are based on the rotational speed of the engine or 111 and 1!
Z, a misfire is detected from fluctuations in acceleration, and if a misfire occurs, it is immediately re-ignited, and the ignition timing is feedback-controlled to adjust the ignition advance angle to MBT (minimum 5par).
kadvance for best torque
e) It has improved exhaust purification performance, fuel efficiency, and two-turn stability compared to Kotoni.

However, in the prior art described in item 1, the sensitivity of the rotational speed or rotational acceleration to the ignition timing is essentially not very good, so it is difficult to determine whether ignition occurred or at what number of ignitions. There was a problem in that sufficient control performance for controlling ignition timing could not be obtained.

In order to solve the above problem, the inventor determined the crank angle at which the cylinder pressure is maximum from the outputs of a pressure sensor that detects the cylinder pressure and a sensor that detects the crank angle, and based on the result, the ignition timing is adjusted. He invented an ignition timing control device that controls the foot hack so that it becomes MBT.

However, in the device described in item 1, simply determining the crank angle at which the cylinder pressure is at its maximum may not provide accurate control.

That is, the cylinder pressure is a combination of compression pressure (also referred to as motoring pressure) generated when the air-fuel mixture in the cylinder is compressed by the up and down movements of the piston, and combustion pressure generated by combustion of the air-fuel mixture.

If the compression pressure is constant under operating conditions (intake air amount as -1), it will be constant regardless of the ignition timing, and only the combustion pressure j will change depending on the combustion state in the cylinder. be.

Therefore, if the ignition timing is to be subjected to fee 1 sequence control to set the ignition timing to MBT, it is necessary to detect the crank angle at which the combustion pressure is at its maximum.

During normal operation, the crank angle at which the combustion pressure is at its maximum and the crank angle at which the cylinder pressure is at its maximum are almost the same, so even if the cylinder pressure is used as is to control It makes no difference.

However, at idle or under low load, the compression is 11:.

Since the combustion pressure is relatively small compared to the force, there is a risk that the crank angle at which the combustion pressure is at its maximum and the crank angle at which the in-cylinder pressure is at its maximum may be mistaken. I can't control it.

This will be explained in detail below.

FIG. 1 is a waveform diagram of cylinder pressure during idling and low load.

Figure 1 (As shown in this figure, at low loads, etc., combustion 1
The difference between the maximum value of the compression pressure (maximum at the dead center '1'' DC) and the maximum value of the cylinder pressure becomes small, depending on the case. As shown in Figure 1H, the maximum pressure may be reached at the TDC point.

Detection of the crank angle at which the cylinder force is maximum is determined by TI
) After C (7) Certain interval, for example from 'rDC to ATDC5
Since the maximum value at one point during the 0° period is detected, in the case of Fig. 1 fc), it will be erroneously determined that the pressure is at TDC or the maximum pressure point.

In such a case, it is determined that the ignition 11. 'In the first period, it moves in the retarded direction.

If the ignition is delayed in the 111th period, the heat generation capacity will further decrease, and the
The 1st power waveform becomes as shown in Fig. 1 (C), so the 111th ignition period is moved to the retard side, and the above operation is repeated until the retard limit W is reached. become.

Also, in the case of Figures 1 (A) and (B), the crank angle at which the combustion pressure is at its maximum and the crank angle at which the cylinder pressure is at its maximum are adjusted to 11", so accurate control (or I end up.

If the ignition timing control becomes abnormal as described above, the drivability and fuel efficiency will deteriorate to 11''.

[Purpose of the invention]

The present invention was made in order to solve the problems mentioned in "-". i Minute only the combustion pressure from the internal pressure jl; II
.

By accurately detecting the crank angle at which the combustion pressure reaches the maximum, feedback control of the ignition stage can be accurately performed. ! One term system (aimed at providing wholesale equipment).

[Summary of the invention]

- In order to achieve the objective 1-1, the present invention provides L
By finding the target waveform for TDC of the 1:1 internal pressure waveform at l1if (13 TDC) from top dead center of Inari, I-IE after two dead center (ATDC)
Find the compression pressure waveform 1. The combustion pressure at ATDC is calculated by subtracting that value from the cylinder pressure.

FIG. 2 is a diagram showing the overall configuration of the present invention.

In FIG. 2, ``■'' is a crank angle sensor that detects the crank angle of the engine, and 2 is a pressure sensor that detects the cylinder pressure.

The storage means 3 also stores the air i before the top dead center of the compression stroke:
1 internal pressure J is stored at every predetermined crank angle (for example, every 2 degrees).

The compression pressure calculation means 4 is stored in the storage means 3.
By calculating the target waveform for the top dead center of the pressure waveform before the dead center, the compression pressure for each predetermined crank angle after the top dead center is calculated. In other words, the pressure values at the target crank angles before and after the top dead center are calculated as being the same with respect to the top dead center.

Next, the combustion pressure calculation means 5 subtracts the output of the compression pressure determination means 4 from the output of the pressure sensor 2 at every predetermined crank angle after the top dead center. Calculate the combustion pressure of

The operation described in item 1 will be explained in detail based on FIG. 3.

shows.

As shown in FIG. 3 (FA), the cylinder pressure P at BTDC is almost just the compression pressure, and this waveform has a value depending on the operating conditions (mainly the amount of intake air).

However, the waveform in ATDC is a combination of combustion pressure and compression pressure, and varies from P1 to P depending on the combustion conditions.
It changes like 4.

On the other hand, since the compression pressure is symmetrical before and after TDC, if we find the symmetrical waveform of the waveform of Po with respect to TDC, we get
Compression pressure waveform P at ATDC. ′ can be found.

Then, by subtracting Po' from P1 to P4, as shown in Fig. 3 (B), < , the combustion pressure P at ATDC
(~P4' can be calculated separately.

Returning to FIG. 2 again, the ignition timing calculating means 6 calculates the ignition timing based on the output of the crank angle sensor 1 and the output of the combustion pressure calculating means 5 mentioned above.

The above calculation is performed as follows.

First, the crank angle θm at which the combustion pressure is maximized is determined from the output of the crank angle sensor 1 and the combustion pressure determined by the combustion pressure calculating means 5, and then the crank angle θm is set so that the above θ becomes a predetermined value. Calculate the ignition timing so that the timing is MBT.

Specifically, the basic ignition timing value (q1 characteristic in Figure 12 below) corresponding to the operating condition at 1 (for example, rotational speed and square load)
1. Calculate the foot hack coefficient for setting the ignition timing to MBT. The actual ignition timing value is calculated by adding that value to the basic ignition timing value.

Next, the ignition timing control means 7 executes the above-mentioned ignition timing calculation means 6.
An ignition signal is sent out at a time corresponding to the ignition timing value calculated in , and the ignition device 8 is operated thereby to perform ignition.

The ignition methods include a method in which ignition is performed only once every - ignition timing, a method in which ignition is performed multiple times at every - ignition timing, and a method in which a misfire is detected and 111 ignitions are performed in the event of a misfire ( For example, Japanese Patent Application No. 57-77536 'E') may be used.

Further, in calculating the ignition timing, it is possible to determine whether or not ignition occurred in the first ignition, and to delay the ignition timing when it is determined that ignition did not occur in the first ignition.

〔Example〕

FIG. 4 is a diagram showing one embodiment of the present invention.

In Fig. 4, the crank angle sensor 1 outputs a unit angle signal MS+ (for example, Fig. 7 31) every time the crankshaft rotates by a predetermined unit angle (1° or 2°), and also outputs a unit angle signal MS+ (for example, Fig. 7 31). 180° for 4-cylinder engines, 120° for 6-cylinder engines)
Every time it rotates, it outputs a reference angle signal S2 (for example, 82 in FIG. 7).

Pressure sensor 2 outputs h pressure 1 signal S3 corresponding to the cylinder pressure.
For example, as shown in FIG. 5, a piezoelectric element 20 press-fitted in the form of a washer between a spark plug 21 and a combustion chamber wall 22 can be used.

The microcomputer 9 has MPU]O, RAMllR
It is composed of an OM 12, an input/output device 13, and the like.

Then, each of the above-mentioned signals St"""Ss is inputted, predetermined calculations are performed, and an ignition signal S4 is output.

The ignition device 8 is a l.lannostar 15. Distributor 162 Ignition flux 17A-17F, Batch 9182 Ignition coil 19
';t.

Then, when the ignition 111 S4 is applied (becomes low level), the to//star 15 is turned off, so that a high voltage is generated in the secondary winding of the ignition coil 19.

The high voltage is applied to the ignition plaque (any one of 17A to 17F) that is in contact with the ignition order through the power distributor 6, and ignition is performed by generating a spark discharge at the cap of the ignition plaque. .

Next, the operation of the microcomputer 9 will be explained. First, the free run counter provided in the input/output device 13 will be explained in 1iij of the overall operation explanation.

FIG. 6 is a block diagram of an example of a free run counter.

In FIG. 6, the edge detector 50 detects the rising edge of the input pulse signal SIO and outputs the detection signal S1.
Outputs 1.

The 16-bit 7-rerunning counter 51 is incremented by 1 every time a predetermined clock pulse (for example, 16/js clock) is counted.

If the timer overflows, the overflow detector 52 outputs the timer overflow interrupt signal S12, and is simultaneously reset to the initial value (ie, $0000).

The input capture register 53 inputs the detection signal Sr+ of the edge detector 50,
The value of the free running counter 51 at < is held.

In addition, the detection signal S11 in "1" is sent to the MAS K register 5.
If the ICF hit of 4 is lj, and the EICT hit is "l", the input capture signal S
As 13, I, MPL via Internal Has 55
J (10 in FIG. 4) is notified, and an input capture interrupt is generated.

Here, as the input pulse signal Sil+, the second
The unit angle signal Sl shown in the figure is used.

The unit angle signal Sl is, for example, as shown at 81 in FIG.
Since the period is 2 degrees in crank angle and the duty is 50%, that is, 1 degree minute is a high level and 1 degree minute is a low level tZJ-less signal, the above-mentioned input capture interrupt is generated every 2 degrees of crank angle. By reading the value of the input capture register 53 at this time, the MPU10 can read the value of the free running counter 51 when the unit angle signal Sl was input.

Therefore, by finding the difference between the previous value of the 7 Lee running counter 5j and the current value, the unit angle signal S1
It is possible to detect the period of

In the present invention, the above unit angle signal 'r3.3. The crank angle em at which the cylinder pressure reaches the maximum value Pm is determined by performing the processing described below using the equation.

Next, the relationship between cylinder pressure and ignition timing will be explained.

FIG. 8 is a waveform diagram of a general in-cylinder w force.

The crank angle θ□ at which the cylinder pressure (strictly speaking, combustion pressure) reaches the maximum value Pm is closely related to the engine's maximum torque and fuel efficiency.
DCjO'~20u), the most efficient operation can be achieved. The ignition timing at this time is M'
It is BT.

Also θ. As shown in FIG. 9, there is a substantially proportional relationship between the ignition timing and the ignition timing, and θ□ can be changed by changing the ignition timing.

Therefore, optimal operation can be achieved by controlling the ignition timing and changing the ignition timing so that θ□ is always at the desired value.

Note that the characteristics shown in Figure 9 indicate that the air-fuel ratio is the stoichiometric air-fuel ratio (Δ/1?1
48) Indicates the case of nearby, hekaraki,・ka12~2
It is known that the tendency is almost the same over a wide range of about 0.

Also, from the characteristics in Figure 9, if θ1,1 is found, i111
It is possible to calculate the timing.

Then, by comparing the 11.5 ignition period of the 11th+i It at that time with the above j′i ignition timing, the 111th
It is possible to determine whether or not the ignition has occurred by igniting the 111+.

Next, detection of θ□ will be explained.

The basic angle signal S2 in FIG. 4 is, for example, as shown in FIG.
° is set to occur.

In addition, a predetermined value between 1 and 60 (equivalent to 2° to 120°) is written in the angle renostar in the input/output device 13 in Fig. 4, and is input after the reference angle signal S2 is input. Unit river biography 7. By counting the number of ;, S, when the crank angle reaches the crank angle corresponding to the value written in the angle register number (assuming the generation point of the reference angle signal S2 as 0), the MPU An angle match interrupt is sent to O.

For example, if the value of Uncle Renostar is set to 9 (equivalent to 18°), then "binary point + 1 if 52° (BTDC 52°)"
An angle match interrupt is performed.

FIG. 10 is a flowchart of a program executed by the above-mentioned angle coincidence interrupt.

As shown in Figure 10, in this interrupt routine the EXT
IRQZ, that is, the free-run counter timer measurement interrupt (hereinafter referred to as input capture interrupt)
Remove the mask.

Specifically, EX of the MASK Lenstar 54 shown in FIG.
TIRQZ hit (EICI hi, y to) wo”O
” Nittle.

In addition, AGLCNT (
Clear the $CA address in memory.

As mentioned above, this angle match interrupt is BTDC52°
Therefore, by canceling the input capture interrupt (IENABLE) in the interrupt routine shown in Figure 10, an input capture interrupt will occur when the next unit angle signal S1 is input manually, and from then on, the input capture interrupt will be generated. An input capture interrupt occurs every time S is input, that is, every 2 degrees of crank angle. Therefore, the input capture interrupt first occurs at 11.1, that is, BTDC5Q°, when the value of the angle register becomes 10, and thereafter occurs every 2° of the crank angle.

This input capture interrupt includes combustion pressure detection shown in FIG. 11, 04. , and a feedback coefficient calculation program.

The following will be explained based on FIG. 11, or first the data names in FIG. 11 will be explained.

AGLCNT is a memory used as a count allocated to address $CA in the RAM, is cleared by the angle match interrupt, and is incremented every time an input/capture interrupt occurs.

1) IMAX is located at address $CB in RAM and stores the maximum value of combustion pressure.

TIIPMX i, t, RAM $CC address split 1
r) La, j1, above I) A for IMAX
The value of GLCNT, that is, the angle in units of 2° calculated from TDC is stored.

THI) MX+ l ~ i'HPMX+6 is the value of 6 consecutive 1" I-T I) M X, that is, all cylinders (6 cylinders in this case) 0) i" HP MX 7) $CD.

$01, $CF, $FO, $F1. It is allocated to address $F2.

ADV F B K is assigned address $F3F3 in RAM, and sets the ignition advance angle to +1.0. This is a data area for feedback control so that the MBT is changed by -1.

1) [BUF is RAM $100~$123
It is assigned to the address, and from BTDC50° to BTDC
A of 24 pressure values measured at 2° intervals
This is a data area that stores D values in order.

Next, FIG. 11 will be explained.

In Figure 11 (A), the square Pl A G L CN
Determine whether it is T or O.

When AGLCNT=Q, crank angle or BTDC50
, and an input capture interrupt is generated for the first time. In this case, go to Pl7 immediately.

When AGLCNT'=;O, all +ij times I/
M signal is sent by put gear interrupt; ;'A of S3
D conversion? JJ (P, 9 below), so P
Go to l and read the AD value that has been completely converted into the A reno star.

Next, J) 3, determine the value of AGLCNT1゜P3
When AGLCNT (25, that is, AGL CN
T Ka] ~24 (B"l" I)C500-BT[
) C2' equivalent to D), P, ~P6te, I/TE,
Kusurenosta X-PI BUF+AGf, CNT-]
is calculated, and the value of the A register, that is, the AD value of the pressure value, is stored in the address corresponding to the value of X, that is, the crank angle at that time.

I) When AGLCNT=25, that is, TDC, go to P7 and clear PIMAX for later processing, then go directly to PI7.

P3teAGLCNT) At 25, Sunaichi AGL
CNT?26~5(] (ATI)C2°~ATDC5
0'), at P6~Pu+, index register X=PIBUF+24-(AGLCNT-25
), 'c (7)

The value of this B renosta is the value of ATDC and TDC, and it becomes the AD value of the royal power value in C.

Next, the value obtained by subtracting the value of 13 Rensta from the value of the A register (the current AD value) read out by P11 and P2, that is, the combustion pressure value at the relevant A i''D C, is calculated as 9 and is read into the A register.

Next, PI2 compares the value of the A register with PIMAX.

P1□, if A is smaller than PIMAX, immediately PI
Go to 7.

When P1□ is A or greater than PIMAX, that is, when the new value of A is greater than the past maximum value, A is stored in PI3 as a new PIMAX.

Next, the value obtained by subtracting 25 from AGLCNT (which becomes the ATDC value) is stored in THPMX as the crank angle at that time.

” - By repeating the process described above, l) IMAX has the following information:
The maximum value of the AI] value of the combustion pressure at ATDC, that is, the maximum value of the compression pressure calculated from the cylinder pressure by 711 is always stored, and
At that time, the value of 8Gf, CNT-25, ie “r”
This means that the crank angle of 2°11)j1'A4 after DC is preserved.

Next, at step 17, after incrementing AGLCNT, go to Pill in FIG. 11 (13) <3°I>,
8, it is determined whether AGLCN T is 50 or not.

If P18 is NO, go to Pl'J and get 1! (Rikishin Bow S
, Af) After starting the conversion, immediately go to ``Outsuri''.

Next, the case where PI8 is YES will be explained.

AGLCNT is 50mm, crank angle is ATDC
500, or at this point, the combustion of l-fuel gas in the cylinder has almost finished. That is, this 1(J
By point ', the combustion pressure has reached its maximum value.

Once, the value of PIMAX at this point and 'j''
I-11) The value of MX indicates the maximum value Pm of combustion force during one combustion cycle and the crank angle θ□ at that time.

1) ls or yl! , S, that is, if AGLCNT=50, 1''< to P2O.

After masking EXTIRQZ in P2O, go to P21.

P21 Teha, THPMX+ l ~THPMX+ 6
1 / Kui 1- Sutsu: / 71・L Ta (7)
H, THPMX+I - THPMX+6.

By doing this, THPMX+1 to THPM
The latest 6 values of 01° are always stored in X+6.

That is, 01° or THPMX11 of the gold cylinder of a 6-cylinder engine.
~THPMX+6.

Next, in P2□ to P26, the current ignition charge factor 1ADVFBK is calculated.

As shown in the characteristics of Fig. 9, in the case of the engine of this example, when the ignition timing is BTDC200, θ+l+ is approximately A
Approximately ATI when TDC18° and BTDC300) C1
1, which is 2°, thus corresponds to the values of THPMX of 9 and 6, respectively.

As mentioned above, "FHP MX-4-1~i" I
f PM X +6 is 11゛j
Since it is written in the correct permutation and number 175, 0111 of the cylinder to be fired next is i" I! P M X -l ('
Recorded in i 1. It's been hot.

The force, 9, square P22, T circle' M X -l-
(Read the value of i and set this value to 8.

Next, in P23, the magnitude of A and 6 is determined.

Generally, there is a close correlation between this θ□ and the maximum torque (best fuel efficiency). It is known to produce the maximum torque (and therefore the best torque).

In the case of this example, it is assumed that θIn, which is the maximum torque, is, for example, 12° ATDC.

ATl) CI2° is equivalent to 6 in THPMx, so
In the case of this example, it is good to control the ignition 111 period so that T HP Mχ is always 6.

I want to do it P2. So, if A=6, it means that +iir ignition timing was appropriate, so go to P24,
Set the feedback coefficient ADVFBK to O.

P2. If A<6, this indicates that the ignition timing is too advanced than the appropriate value, so the program goes to P25, sets the feedhack coefficient ADVFBK to -1, and controls the ignition timing to retard.

P2 Ute A) 6 indicates that the ignition timing is behind the appropriate value, so go to P2O, set the feedback coefficient A I) V F B K to +1, and control (display) the ignition timing to advance. do.

Next, use P27 to set the value of 6 ADVFBK for 6 cylinders to 1.
After tufting Hyde, ADVFBK+l~A I
) Store V1'BK+6i.

By doing this, ADVFBK +1-ADVFB
In K+6, the values of six foot hack coefficients are assigned to the firing order of each cylinder (for example, 1st, 5th, 3rd, 6th, 2nd, etc.).
It will be held after being circulated sequentially according to the number 4 cylinder).

Therefore, it always indicates the value held in ADVFBK+6 or the feedback coefficient of the cylinder to be ignited next time.

Therefore, the value of ADVFBK+6 is read out as the feedback coefficient ADVFBK.

Next, from P28 to P30, ignition 11. Calculate the l1 period.

First, in P28, the basic ignition timing value is calculated from the engine rotational speed N and the load information.

This procedure is similar to conventional ignition timing control, and for example, the ignition 111 stage value (advance value) corresponding to the rotational speed and load 11F as shown in FIG. A method is used in which the value is stored and read out a value corresponding to the rotational speed and load i, i; i: at that time.

Note that the load amount is intake air ir, i:, intake negative 11
: or fuel injection pulse llI Tp (to the intake air; calculated from : and rotational speed), etc. can be used.

In addition, the basic ignition timing value ■. In addition to the above calculation methods, there are also methods to calculate from only the rotational speed or from the suction credit. There is also a method that controls with different characteristics when the throttle valve is fully closed (idling) and at other times. .

Next, in P29, the foot bank coefficient ADVFBK is added to the basic ignition timing value [0 indicated by -lx to calculate the actual ignition timing value 111j.

Next, the ignition timing value 1+< of "1" is outputted at P2O, and the ignition II"1 period restriction 1 is performed in accordance with that value.

The force control of the ignition I+,', period control is the same as the conventional one.

For example, if it occurs at S2 or BTDC 70°, store the value of 70-11+ in Renostar, and then manually input the value of 70-11+ after manually performing S2 or S2. The configuration may be changed so that the ignition signal uS4 is output when the unit angle is reached.

In addition, in the explanation of item 1-1, the case where fee 1-hack control is simply performed to set the ignition timing to MBT is given as an example, or in the case of one set (in which ignition is performed multiple times at each ignition timing),
There is also a method in which it is determined whether or not ignition occurred during the first ignition, and the feed hack coefficient is changed accordingly.

The above method is performed by inserting P31 and P32 next to P22 in FIG. 11(B), as shown in FIG. 11(C), for example.

That is, for example, the first ignition period of 114° is BT, DC2.
When set to 5°, as can be seen from the characteristics in Figure 9,
If ignition occurs on the first ignition, θIII is ATD
ATDC14°, which is C14°, corresponds to THPMX.

Therefore, if P31 is A or 8 or higher, the first [1
It can be determined that the ignition was not caused by the ignition of the ignition.

Note that the value (8 in the 1-example) used as the basis for comparison /'llf changes depending on the ignition timing value.In other words, in this example, if P31A is 8 or more, In the case of
If the ignition did not occur on the second ignition, in such a case it is necessary to delay the ignition timing as a whole, so go to P+12 and set the footback coefficient ADVFBK to -1.

P31 is either A or 8' (i? In the case of i, it is the case that 71 fires were fired at 11-' in the first ignition. In that case, go to P23 and determine the size of A and 6. do.

The following processing is the same as that in FIG. 11 (13) in +1ir.

As described above, by determining whether or not the ignition occurs at the first ignition, the ignition timing can be precisely controlled.

〔Effect of the invention〕

Below-1-: As explained, in the present invention, compressed row 4
AT
The combustion pressure at ATDC is calculated by finding the compression pressure at DC and subtracting that value from the cylinder pressure, so the crank angle at which the combustion pressure is at its maximum is always accurately detected. I can do it, I
” The ignition IL'l' period can be accurately controlled even during IJ operation or at low load.

[Brief explanation of drawings]

Fig. 1 is a cylinder pressure characteristic diagram at low load, Fig. 2 is a diagram showing the overall configuration of the present invention, Fig. 3 is a characteristic diagram of cylinder pressure, compression pressure, and combustion pressure, and Fig. 4 is a diagram showing the characteristics of the cylinder pressure, compression pressure, and combustion pressure. FIG. 5 is a diagram of an example of a pressure sensor, FIG. 6 is a block diagram of an example of a free run counter, FIG. 7 is an example of an output waveform of a crank angle sensor, and FIG. 8 is a diagram of an example of a cylinder. A characteristic diagram of internal pressure, FIG. 9 is a diagram of the relationship between ignition timing and θ□, FIG. 10 is a flowchart of a program executed by angle coincidence interrupt, and FIG. 11 is a flowchart showing an example of the calculation of the present invention. 1., FIG. 12 is an example diagram of basic ignition timing values of 9 to .degree. Explanation of the bow ■...Crank angle sensor 2...Pressure case sensor 3...Storage means 4...Usage 11 yen 9 fixed stage 5...
Combustion pressure calculation means G. Ignition timing control 9T', Stage 7. Ignition timing control means 8.. Ignition system i'3' Attorney Junnosuke Nakamura f1 Figure (A) ''lrZ Figure

Claims (1)

[Claims] In the ignition timing control device 1' which controls the ignition timing according to the operating state of the internal combustion engine, a crank angle detection means detects the crank angle of the engine, and Ll detects the cylinder pressure:
, a force detecting means, a memory means for storing the pressure in the cylinder before the top dead center of the retraction stroke for each predetermined crank angle, and a binary point 11 detected by the pressure detecting means; From the previous pressure value, the compression at each specified crank angle after top dead center is calculated by assuming that the pressure values at crank angles before and after two dead centers are the same for two dead centers. a compression pressure calculation means for calculating the pressure; and a compression pressure calculation means for calculating the pressure at every predetermined crank angle after top dead center by subtracting the compression pressure mentioned above from the cylinder pressure detected by the pressure detection means at every predetermined crank angle after two dead center. Combustion pressure calculation 1 to calculate the combustion pressure of
Then, the crank angle em at which the combustion pressure is maximum is detected from the combustion pressure value obtained by the combustion pressure calculation means, and the value θm is calculated.
ignition timing calculation means for calculating the ignition timing so that the ignition timing is set to a predetermined value of 11?1'' after top dead center, and ignition timing control means for controlling the ignition timing in accordance with the calculation result of the ignition timing calculation means. A sighting device.