JPH0552435B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an ignition timing control device for an internal combustion engine using a finger pressure detection method.

BACKGROUND ART It is known that the internal combustion chamber pressure changes when an internal combustion engine is in operation as shown by curve A in FIG. In other words, when the ignition system is triggered at the ignition angle θ _IG , the air-fuel mixture is ignited with an ignition delay θd, and the cylinder internal pressure then follows a process of rapidly rising, reaching the maximum pressure peak Pmax (hereinafter referred to as the shiatsu peak), and then dropping. .

It is known that the crank angle position of this shiatsu peak is related to the state in which the engine exerts its maximum output, and the crank angular position of the shiatsu peak that can provide this maximum output is at top dead center as shown in the figure. After (hereinafter referred to as ATDC) For example, 12° to 13°
It was experimentally confirmed that. Therefore, an ignition timing control device using a finger pressure detection method that controls the ignition timing θ _IG so that the finger pressure peak falls within the ideal peak range with ATDC 12° to 13° as the ideal peak range is disclosed in, for example, Japanese Patent Publication No. 49-29209. It is known by.

Such an ignition timing control device directly detects the cylinder internal pressure, obtains shiatsu peak position data for each engine cycle using a shiatsu signal representing the cylinder internal pressure, and advances the ignition timing for each engine cycle by comparing it with target position data. Or, it is designed to be delayed.

By the way, when the engine is operating normally, the maximum peak of the cylinder internal pressure change occurs near top dead center, as described above, but when the engine is abnormal or the shiatsu detection signal system is abnormal, the shiatsu signal changes as shown in Figure 1. It does not change like the curve shown above. As such an abnormality detection method, a technique is known from Japanese Utility Model Application Laid-Open No. 59-49788, which detects an abnormality by observing changes in the acupressure peak value within one engine cycle.

On the other hand, when trying to obtain a finger pressure detection type ignition timing control device that can be used for both 2-stroke engines and 4-stroke engines, it is necessary to detect the intake and exhaust process in the 4-stroke engine as a so-called fire cycle. Since this is not an abnormal state, the technique described in the above-mentioned Japanese Utility Model Application Publication No. 59-49788 cannot be applied.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an ignition timing control device for an internal combustion engine using a finger pressure detection method, which can detect the so-called burn-off cycle and perform accurate control without using a special device.

In the ignition timing control device for an internal combustion engine according to the present invention, the previous value and the current value are compared among the Shiatsu peak value data continuously obtained for each engine cycle, and the current value is greater than or equal to a predetermined value compared to the previous value. If it is significantly smaller, the current cycle is determined to be a discarded cycle, and the current shiatsu peak value is replaced with the previous shiatsu peak value.

Embodiment FIG. 2 shows an ignition timing control device according to the present invention. In this device, a through hole is formed in a member such as a cylinder head that forms a combustion chamber of an internal combustion engine (not shown), and a piezoelectric A finger pressure signal generating circuit 1 is included, which is obtained by closely inserting a pressure sensor of the element so that its detection head is exposed inside the combustion chamber. For example, the clock generation circuit 2 synchronizes with the engine rotation and generates a signal every engine cycle.
Generates 360 clock pulses. As a means for obtaining clock pulses synchronized with engine rotation, a photocoupler is combined with a slit disk that rotates in response to the rotation of the crankshaft and has a large number of slits at equal intervals, and the clock pulse is generated by the output signal of the photocoupler. There are known means for obtaining . The reference position generating circuit 3 generates a reference position signal indicating that the crank angle position has reached a reference position corresponding to, for example, 90 degrees before top dead center (hereinafter referred to as BTDC). This reference position signal can be obtained by separately providing a reference position signal slit in the slit disk used in the clock generating circuit 2 and providing a reference position signal generating photocoupler. The peak hold circuit 4 holds the maximum value of the acupressure signal after being cleared by the reference position signal. A comparison circuit 5 is connected to the peak hold circuit 4. The comparison circuit 5 generates a peak detection signal when the acupressure signal itself falls below the maximum value.
A counter 6 for measuring the crank angle position counts clock pulses and is cleared by a reference position signal, and the count value θc of the counter 6 is, for example, 8-bit data and indicates the current value of the crank angle. The latch circuit 10 latches the count value of the counter 6 every time the peak detection signal from the comparator circuit 5a is supplied to its gate terminal g. On the other hand, the decoder 11 uses the counter 6
When the count value reaches, for example, 154, a read command signal is supplied to the ignition angle setting circuit 8. count value
154 corresponds to a crank angle that is larger than the crank angle at which the acupressure peak value is predicted to occur, and obtains a reading timing that is not affected even if the valve seating noise of the exhaust valve mixes into the acupressure signal. There is. In response, the ignition angle setting circuit 8 reads the contents of the latch circuit 10 and determines the latch contents as peak position data θpx on the crank angle. It is also possible to consider a configuration in which the latch contents are supplied to the ignition angle setting circuit 8 via a gate circuit that opens the gate in response to a reading command signal from the decoder 11. The ignition angle setting circuit 8 is constituted by a microprocessor or the like, and based on the supplied peak position data θpx, according to a program described later,
The desired ignition angle θ _IG data is supplied to the ignition command circuit 9. The ignition command circuit 9 learns the current crank angle value from the count value θc of the counter 6, and when this count value θc and the input θ _IG match, the ignition command circuit 9 switches the ignition switch.
The SW is opened, and as a result, ignition current flows through the secondary coil of the ignition transformer T, causing ignition at the ignition plug (not shown). Incidentally, the ignition angle setting circuit 8 and the ignition command circuit 9 form an ignition command means. The ignition angle setting circuit 8 may also have a mode in which the ignition angle setting circuit 8 operates based on various engine parameters from the engine parameter sensor 12, such as engine speed Ne, intake negative pressure P _B , throttle opening θth, and engine coolant temperature Tw. Further, the ignition angle setting circuit 8 supplies the A/D converter 13 with comparison reference data of the comparison circuit 5b.

3A to 3F are signal waveform diagrams illustrating the operation of the above embodiment circuit. That is, the reference position signal and clock pulse are as shown in FIGS. 3A and 3B, respectively. The acupressure signal changes as shown by the solid line in FIG. 3C, and therefore the output of the peak hold circuit 4 changes as shown by the dotted line in FIG. 3C. The comparison circuit 5 generates a peak detection signal as shown in FIG. 3D at each maximum point of the acupressure signal. FIG. 3E shows numerically how the count value θc of the counter changes.

FIG. 3F shows numerically how the latch contents of the latch circuit 10 change. FIG. 3G shows the change in the output of the decoder 11, in which case the high level is the read command signal.

The ignition angle setting circuit 8 determines whether or not a reference position signal is generated as shown in FIG. 4 (step S ₁ ).
However, when the reference position signal is generated, engine parameters such as engine speed Ne, throttle opening θth, etc. are taken in from the engine parameter sensor 12 (step S ₂ ). After step _S2 , or when the reference position signal is not generated, it is determined whether or not a reading command signal has been generated (step _S3 ), and when the reading command signal is generated, the maximum Read the peak value Pmax (N) (step
_S4 ). Next, the engine rotation speed Ne (N) is determined as the discriminant value.
Compare with Ner (step S ₅ ). If Ne(N)<
If Ner, it is determined whether the value obtained by subtracting the previous value Pmax (N-1) from the current peak value Pmax (N) is greater than ε (step S ₆ ). Ne(N)＞
Ner, and if the current value Pmax (N) is smaller than the previous value Pmax (N-1), step _S6 is entered (step _S7 ). On the contrary, Pmax (N) < Pmax
(N-1), it is determined that the engine is braking, and the ignition angle θ _IG is set to a value retrieved from the engine braking ignition map using the engine speed Ne, etc. as a parameter (step S ₈ ).
Note that the engine brake state may be identified by Ne(N)>Ner and the throttle opening θth being smaller than a predetermined value θr.

If Pmax(N)>Pmax(N-1)+ε,
Since it is estimated that an explosion occurred in this cycle, the peak position θpx (N) is assumed to be the correct value and the next step _S9 is entered. However, Pmax(N)<
In the case of Pmax (N-1) + ε, no explosion has occurred in this cycle, and the correct peak position θpx cannot be expected regardless of whether the intake/exhaust stroke in a 4-stroke engine is an arrow cycle or not. It is determined that it is a cycle. Therefore, in this case, the current value θpx (N) is the previous value θpx
(N-1) (step _S10 ), and enters step _S9 . In step _S9 , in order to increase the stability _of ^the feedback system, past engine cycles (N-
1), (N-2), ... The current data value is corrected based on the acupressure peak position data value in the (N-n)th engine cycle.

As a specific example of ωn in the above formula, ω ₀ = ω ₁ = ω ₂ =
Assuming ω ₃ = ω ₄ = 1/5, ω ₅ = ω ₆ =…=ωn = 0,
It is also possible to use the average value of the past four data and the current data as the current data. The averaging method is not limited to this, but the average of data an appropriate number of times is taken. Also, ωn=(1/L) ⁿ (L>1, n
>0) may also be considered.

It is determined whether θpx thus obtained is greater than the sum of the top dead center angle θ _TDC and the angle α of, for example, 12° (step S ₁₁ ), and if so, the ignition angle θ _IG is advanced by Δθ ₁ . Set the angle (step S ₁₂ ), if small, ignition angle θ _IG
is retarded by Δθ ₂ (step S ₁₃ ). Here, the advance angle amount Δθ ₁ and the retard angle amount Δθ ₂ are not necessarily set to the same value, but depending on the characteristics of the feedback system, Δθ ₁ >
θ ₂ or Δθ ₁ <θ ₂ . Also,
Δθ ₁ and Δθ ₂ can also be functions of the difference between θpx(N) and (θ _TDC +α).

The operation of one cycle of steps _S1 to _S20 from the start to the end described above is executed sequentially in response to the above-mentioned clock pulse or a clock pulse of a predetermined period other than this, and the cycle operation is repeated. The following programs are also similar in this regard.

In this operation, feedback control is performed so that the peak position data θpx is equal to θ _TDC + α, but the peak position data θpx is equal to θ _TDC + α±
It is also possible to control the value to be within the range of β(X). Here, β(X) is the engine speed
It can be set by any one of Ne, throttle rotation θth, and engine suction negative pressure P _B , and by doing so, it is possible to improve the stability of the entire feedback system.

FIG. 5 shows an example of an operating program when the ignition command circuit 9 is formed by a microprocessor. That is, the ignition command circuit 9 takes in the ignition angle data _θIG from the ignition angle setting circuit 8 (step S ₂₁ ), and takes in the count value θc from the counter 6 (step S ₂₂ ). It is determined whether this ignition angle data θ _IG and the count value θc match, and θ _IG = θc
Immediately when the following conditions are met, an ignition command is issued (steps _S23 , _S24 ) to open the ignition switch SW. In step _S23 , instead of determining whether θ _IG =θc, it may be possible to determine whether the difference between θ _IG and θc is smaller than δθ.

Effects of the Invention As is clear from the above, in the ignition timing control device for an internal combustion engine according to the present invention, a large sample value can be obtained by comparing two consecutive sample values of the finger pressure peak value for each engine cycle. The cycle is determined to be an explosion cycle.
Since the acupressure peak signal is used to distinguish between the explosion stroke and the exhaust suction stroke or misfire cycle without using a sensor such as a crankshaft rotational angle position sensor, the system is low-cost and operates accurately. .

[Brief explanation of the drawing]

Fig. 1 is a graph illustrating internal pressure changes in an engine cylinder, Fig. 2 is a block diagram showing an embodiment of the present invention, Fig. 3 is a signal waveform diagram showing the operation of the device shown in Fig. 2, and Fig. 4 and FIG. 5 is a flowchart showing the operation program of the portion constituted by the microprocessor of the apparatus of FIG. Explanation of symbols of main parts, 8...Ignition angle setting circuit, 9...Ignition command circuit, 10...Latch circuit,
11...Decoder, SW...Ignition switch, T...
...Ignition transformer.

Claims (1)

[Scope of Claims] 1. Reference position signal generating means that generates a reference position signal every time the crank rotational angular position of the internal combustion engine reaches the reference angular position, and acupressure signal generating means that generates a fingerpressure signal representing the internal combustion chamber pressure of the engine. and peak detection means for generating an acupressure peak value and position signal representing the maximum peak value and position of the acupressure signal from generation of one reference position signal to generation of the next reference position signal, An ignition timing control device comprising an ignition command means for commanding ignition at a certain ignition angle, the ignition command means controlling an abnormal cycle when the current value of the finger pressure peak value is smaller than the previous value by a predetermined value or more. An ignition timing control device for an internal combustion engine, characterized in that the current shiatsu peak position signal is ignored based on the judgment. 2. The ignition timing for an internal combustion engine according to claim 1, wherein the ignition command command means replaces a previous value with the current value of the command peak position signal when determining the abnormal cycle. Control device. 3. The ignition timing control device for an internal combustion engine according to claim 1 or 2, wherein the ignition command means does not discriminate the abnormal cycle when detecting an engine brake state.