JPH0692791B2 - Flame light detector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flame light detection device for detecting the combustion state of an internal combustion engine, and more particularly to a flame light detection device capable of controlling the entire operating range with high accuracy.

[Background of the Invention]

To keep the combustion of the internal combustion engine always good, the combustion temperature,
It is necessary to optimally control the pressure, air-fuel ratio, ignition timing, etc. It is also well known that it is advantageous to operate near the limit of occurrence of knock in order to further improve the output and economy. A number of methods for detecting any of these parameters and performing closed-loop control have been proposed so far, and among them, a method of detecting the above parameters by combustion flame light has also been proposed. As this flame light detector, for example, JP-A-57-108734,
As disclosed in JP-A-54-108735, a quartz screw rod is arranged on the combustion chamber side and an optical fiber is arranged on the other end side in a metal screw casing, as disclosed in JP-A-57-163842 and JP-A-58-102131. As described above, there is a spark plug in which the above-mentioned flame light detection section is incorporated.

The biggest difficulty with this type of flame photodetector is that the flame charge detection surface (the surface that contacts the combustion flame) becomes dirty due to the deposition of oil, tar components contained in gasoline, carbon, etc., and the flame light transmission efficiency. Is reduced. That is, the ability to detect flame light is reduced.

Therefore, the above-mentioned JP-A-57-108734 and JP-A-57-10.
In 8735, quartz glass with excellent heat resistance was installed in the high temperature part of the combustion chamber to burn out dust with a combustion flame, and in JP-A-57-157436 and JP-A-57-175240, a standard emission source was used. Detects the degree of contamination of the flame light detection surface by the light of
It presents a method of adding correction to the flame detection signal. Further, Japanese Patent Laid-Open No. 163842/1982 proposes a method for cleaning and burning out the flame detection surface with a mixed air flow and a discharge spark flow. In any case, it is extremely difficult to suppress the adhesion of dust to the flame light detection surface to the extent that it does not affect the detection sensitivity, and the correction method using the reference light also has problems such as complicated structure and cost up. .

[Object of the Invention]

It is an object of the present invention to solve the above-mentioned problems of the combustion flame photodetector, and to provide a combustion flame photodetector with a simple configuration, high accuracy, and high reliability over a wide operating range. is there.

[Outline of Invention]

The feature of the present invention is that the area of the engine operating state in which dust adheres to the flame detecting surface is obtained in advance, and in the case of the above area by the information signal indicating the operating state of the engine, the flame detecting is performed. The purpose is to cut off the detection signal from the device and switch to open loop control.

According to a preferred embodiment of the present invention, in the operating region where no adhesion occurs, the true ignition timing is detected from the flame light signal, and the ignition timing is optimized by the closed loop control.

Also, when entering the other operating area from the operating area where the above adhesion occurs in a short time, the flame light detector is delayed by an arbitrary time in consideration of the time required to incinerate the dust on the flame light detecting surface. The signal is used for closed loop control.

Example of Invention

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an embodiment of the overall configuration of the flame light detection device according to the present invention. Here, the case of a normal four-cycle engine is illustrated. The engine 10 includes a piston 11, an intake valve 12,
A combustion chamber 15 is formed by the exhaust valve 13 and the spark plug 14. A flame light detector is used to detect combustion flame light in this combustion chamber.
16 are installed. The rear end of the fire charge detector is guided to a photoelectric converter 18 via an optical fiber cable 17, converted into an electric signal, and a signal processing circuit 20 via a switching circuit 19.
Then, predetermined signal processing is performed and the signal is guided to the controller 21 . The detection signal of the parameter detector 22 of the engine operating state is input to the controller 21 , and the ignition timing, the air-fuel ratio, etc. are calculated by calculating the optimum control value or the map processing according to the operating state. Output. FIG. 1 shows only the case of ignition timing control. The ignition timing control signal determined and output by the controller 21 is sent to the ignition device 23, and the high-voltage ignition signal is sent to the spark plug, and spark discharge occurs at a predetermined time to cause combustion. Here, when entering the operating region where dust adheres to the combustion chamber side detection surface of the flame light detector 16 described above, the controller 21 senses this from the signal of the parameter detector 22, and the switching circuit 10 and the signal are detected. A command signal is issued to the processing circuit 20. As a result, the flame light signal is input to the controller 21 and cut off. Therefore, in this case, the controller 21 temporarily cancels the closed loop control mode by the flame light signal and executes the control in the open loop mode.

FIG. 2 shows the experimentally obtained results of the engine operating region where dust adheres to the flame photodetector. The area is determined by the engine speed N and the load, and the area A shown in the figure is most likely to have dust adhered thereto, while the area B has adhered thereto, but the amount thereof is relatively small. Further, in the C region, the decrease in flame light transmittance due to dust adhesion is almost negligible. Therefore, the detection signal from the flame photodetector may be used as an effective signal outside the areas A and B, that is, in the area C.

Further, engine cold operation i.e., start-up, in such warm-up operation range, as shown in FIG. 3, with the decrease of the engine coolant temperature T _W, and dark air-fuel ratio of the mixture supplied to the engine stability It is necessary to make a proper combustion. Also,
In such an operating state, it is necessary to maintain the intake air amount with respect to T _W as well as an arbitrary increase characteristic. Therefore, in such an operating region, the dust deposit zone cannot be represented only by the deposit map shown in FIG. That is, the adhesion map shown in FIG. 2 is after completion of warming up, and the other region, that is, the boundary value T of the water temperature shown in FIG.
If less has decreased to _WX, changing the Katsuhito region of the closed-loop control by the operation region i.e. the flame light signals by connexion deposition zone within a predetermined correction coefficient K _W.

FIG. 4 shows an example of the method for cutting the flame light signal when it enters the adhesion zone. The photoelectric converter 18 shown in FIG. 1 is composed of the phototransistor 24 in FIG. 4, a fixed resistor R ₁ 26 connected to the emitter and an adjusting resistor R ₂ 27, and the emitter is connected from the power supply voltage V _B side according to the light quantity. The amount of current flowing to the side changes. Along with this, the voltage level on the emitter side changes, and this is output as a flame light signal. This output signal V _f inputs the analog switch 25. The control signal V _C is input to the analog switch 25 from the controller 21. When V _C is at a high level (C zone in FIG. 2), the input signal of V _f remains unchanged from the analog switch 25. Is output. On the other hand, when V _C is at a low level (zones A and B in FIG. 2), the analog switch 25 outputs a signal of 0 volt.
The signal output from the analog switch 25 is a signal processing circuit.
Guided to 20. When V _C is low level, the operation of the signal processing circuit 20 may be stopped by this V _C signal. Further, without using the V _C signal, the operation of the signal processing circuit 20 may be stopped if the input signal from the analog switch 25 holds 0 level for an arbitrary required time. When V _C is at a high level, the signal processing circuit 20 also inputs a signal from the controller 21 and performs a predetermined signal processing, and outputs the result to the controller 21 .

Here, it is natural that the signal processing by the closed loop control varies depending on the detection target, but in the embodiment of the present invention, the case of true ignition timing detection will be described. Fifth
The figure shows a waveform of the relationship between the spark discharge timing (commonly referred to as ignition timing) and the combustion start timing (this is the true ignition timing) with respect to the top dead center timing of the piston. FIG. 5 (a) shows the top dead center signal, and the TDC position shown is the top dead center. (B) is an ignition signal waveform, and spark discharge has started at time t ₁ . That is, spark discharge is performed by the spark plug at a timing earlier than the top dead center TDC by the engine crank angle θ _S. However, combustion of the air-fuel mixture in the combustion chamber does not start immediately due to this spark discharge, and it takes some time for the spark nucleus generated by the spark to grow,
After that, since it propagates to the combustion chamber as a hot flame, that is, the combustion starts, the combustion starts with a delay of θ _D from the spark discharge start timing (Fig. 5 (c) shows a detection signal of the flame photodetector). This θ _D is called flame propagation delay, and the parameters that affect it are (a) combustion chamber pressure, (b) spark plug electrode part, (c) mixture state, (d) fuel properties, etc. There is. Here, even if the engine is operated with the constants (a), (b), and (d), θ _D fluctuates every cycle due to the influence of (c). In extreme cases, the crank angle fluctuates more than 10 degrees. Θ _C for the go-between, but, TDC
Although the timing t _{2 which} is deviated by only this is the true ignition timing, since this θ _C fluctuates every cycle, when controlling the ignition timing from this signal, the average value _C for several cycles is set to the true ignition timing. It is effective to use it as a timing signal. Further, when the combustion starts, the flame light signal (c) rises sharply, and the combustion becomes inactive and falls. The peak period theta _FP flame light signal corresponds well theta _C described above, theta _C
Is larger than before top dead center, that is, when combustion starts early, θ _FP reaches a peak near the top dead center, and when θ _C is small before top dead center, that is, when combustion starts late. The θ _FP peaks at a late time away from top dead center. Therefore, the true ignition timing θ _C can also be obtained by extrapolation by the detection of θ _FP . When dust adheres to the flame light detector, the output level of the flame light detection signal of FIG. 5 (c) decreases from (c) -1 to (c) -2. However, the above θ _FP does not change, so θ _FP
The method of obtaining θ _C more has the advantage that it is less susceptible to dust adhesion.

Hereinafter, a case of performing the ignition timing control by detecting the above-mentioned θ _C by the flame light detector and a case of similarly detecting the θ θ _FP and performing the ignition timing control will be described.

FIG. 6 shows a signal processing method when the ignition timing control is performed by detecting θ _C. The flame light signal (c) is 2 in the case of a four-cycle engine, compared to the top dead center signal (a).
Once in a time. The judgment line (d) is set at a slice level slightly higher than the 0 level of the flame light signal (c), and when the flame light signal (c) is larger than the judgment line D, a signal (e) that becomes high level is generated. On the other hand, the waveform of the top dead center signal (a) is shaped to generate the signal (f). Therefore, when a pulse such as (g) that becomes a low level when (e) becomes a high level and (e) becomes a high level and (f) becomes a high level is generated, a high level period of this pulse is generated. Substantially corresponds to the true ignition timing θ _C shown in FIG. It will be. This θ _C is calculated in time units,
Ultimately, it is necessary to obtain the engine crank angle.
Therefore, when the pulse of (f) is input while (e) is at a high level, a pulse signal (h) is set which is reset to a high level and reset by the next pulse of (f). This is the time T required for one revolution of the engine, and the crank angle is 36
Since it is 0 °, the value at the crank angle of θ _C can be obtained from the time ratio of the high level timings of the pulses of (e) and (g). The pulse high level period of (g) is (i)
When the count ends, the pulse is held until the pulse of the value (h) becomes low level, and during the hold period, for example, (e) is high level and (f) is from high level to low level. At the point of change, the held count value is immediately stored in the storage device in the controller.

Further, the high level period of (h) is counted by the counter as in (j), and when the counting is finished, the value is held until the pulse of (g) becomes high level.
The hold value is stored in the storage device in the controller at a point where (e) changes to low level and (f) changes from high to low level.

Needless to say, both of them are taken into the controller via the A / D converter. The controller obtains the average value of each of these values when it has been taken in several times, and the former, that is, the crank angle timing of the true ignition timing θ _C is calculated by the calculation because the latter takes 360 °. When the obtained crank angle timing deviates from the preset crank angle timing by the control tolerance or more, a correction value of the ignition timing is applied to the ignition device 23 so that the deviation becomes 0, and the ignition timing at the ignition plug 14 is set. To control properly. This operation is repeated until both values are within the predetermined control tolerance. However, this operation is not performed immediately after the operating state changes and when the above-mentioned dust adhering zone is entered.

Next, the case of performing the ignition timing control by detecting the peak timing θ _FP of the flame light signal will be described with reference to FIG. 7. The same waveforms are indicated by the same symbols as in FIG. The top dead center signal (a) and the flame light signal (c) are processed as follows. The signal (c) is differentiated and becomes like (c) '.
The peak time of (c) is a boundary point at which the curve of (c) 'changes from positive to negative, and at this point, a high level pulse is generated as in (k). On the other hand, the top dead center is converted into a waveform every (f). Next, when the pulse of (k) becomes high level, it is set to high level, and when the pulse of the next (f) becomes high level, it is reset and becomes a low level pulse signal (l). Then, when (f) becomes high level, it is set to high level, and when (l) becomes high level, it is reset and low level pulse signal (m) is produced. This is the time width of the peak timing θ _FP of the flame light signal. Next, when (m) becomes a high level, it is set to a high level, and when the next (f) becomes a high level, it is reset and becomes a low level pulse signal (h). This is the time width required for one rotation for a crank angle of 360 °. The high level periods of the pulses of (m) and (h) are counted and held as in (n) and (o), respectively, and the values are stored in the controller several times as in the case of FIG. A true ignition timing is obtained by averaging and arithmetic processing, and ignition timing correction control is performed based on this.

The ignition timing generally referred to here is the spark discharge start timing θ _S as described in FIG. 5, and the true ignition timing θ _C is θ _C =
θ _S −θ _D is represented. Here, as shown in FIG. 8, the relationship between θ _S and θ _D changes depending on the magnitude of the intake pipe pressure P _B (corresponding to the load) even when the engine speed N is kept constant. That is, the value of θ _D changes depending on N and P _B. Therefore, in order to determine the true ignition timing θ _C from the detection signal of the flame photodetector and to determine the spark discharge start timing θ _S , the so-called ignition timing from this with the spark plug,
θ _C = θ _S + θ _D, that is, θ _D needs to be given each time. In this case, it may be obtained from a functional expression of θ _D = f (N, P _B ), or the map of N and P _B can be obtained by θ _D
It is also possible to memorize each of the values and to read out θ _D of the corresponding operating state.

Ignition timing control may be performed by the method shown in FIGS. 9 and 10 except in the above-mentioned dust adhesion zone. That is,
As shown in FIG. 9, the optimum set value of the true ignition timing θ _C determined by N and the load is mapped, and θ _{D at} that time is also mapped as shown in FIG. When θ _C and θ _D of the corresponding operating range are determined, the spark discharge timing (ignition timing) θ _S at the spark plug is determined from θ _C = θ _S + θ _D , and this value is used to cause spark discharge at the spark plug. . With this, the timing of combustion, that is, the true ignition timing (here, it is a detected signal, and is therefore θ _C ′) is obtained, and θ _C and θ
If there is a difference in _C ′, θ _S is changed so as to make it zero. If both match or fall within an arbitrary tolerance, the θ _D value at that time is updated and stored in the map of FIG. 10. That is, when the learning control function is added, the controllability is further improved. In the case of the dust adhesion zone, θ _S may be determined from the maps shown in FIGS. 9 and 10 and open loop control may be performed, or θ determined by N and the load separately.
It may be determined Yotsute θ _S to Matsupu of _S. Here, in the case where a learning control function other than the adhesion zone is added, θ _D at the time of open loop control of the adhesion zone is taken into consideration in consideration of the deviation of the learned value updated from the previously learned learned value.
Alternatively, if the θ _S value of the separately provided map is rewritten, the ignition timing control can be optimized even in the open loop, and the efficiency of the engine can be extremely improved.

Next, when entering the operating range of zone C where no dust adheres from the operating range of zones A and B shown in Fig. 2 where dust adheres,
It takes some time for the dust adhering to the end of the flame photodetector to burn out, so the closed loop control of the ignition timing must be started with a delay of that burnout time. When the controller 21 senses that such a state has been reached by the detection signal of the parameter detector 22, the controller will pass several cycles or an arbitrary time with the top dead center signal from the time of sensing. without control signal V _C shown in FIG. 4 to the high level, the signal processing circuit 20 to the flame light signal
The ignition timing closed loop control based on the flame light signal is performed as a high level after the lapse of this predetermined cycle or time without being guided to the side.

〔The invention's effect〕

According to the present invention described above, it is possible to avoid the influence of dust adhering to the flame photodetector, and in addition, in an operating range in which no dust adheres, it is possible to control the ignition timing to an extremely high precision with optimum precision, and even in an operating range where dust adheres. Since the ignition timing can be corrected by referring to the ignition timing learning control value in the former operating range,
Highly accurate ignition timing control is possible in all operating ranges.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing an attachment zone of dust attached to the tip of a flame photodetector. Figure 3 shows A / with respect to the engine cooling water temperature.
FIG. 4 shows the change characteristics of F, FIG. 4 shows the circuit configuration block of the flame light signal switching unit, and FIG. 5 shows the relationship between flame light, top dead center, and spark discharge waveform. FIG. 6 is a time chart for obtaining the true ignition timing θ _C from the rising point of the flame light signal,
FIG. 7 is a time chart for obtaining the peak timing θ _FP of the flame light signal. FIG. 8 shows the relationship between the spark discharge timing θ _S and the combustion propagation delay θ _D , and FIGS. 9 and 10 show the maps of θ _C and θ _D. 14 ... Spark plug, 16 ... Flame light detector, 18 ... Photoelectric converter, 19 ... Switching circuit, 20 ... Signal processing circuit, 21 ... Controller.

Claims (3)

[Claims] 1. A flame photodetector whose one end is opened in a combustion chamber of an engine, an optical fiber for guiding an optical signal of the flame photodetector, and an optical signal guided by the optical fiber. Photoelectric conversion means for converting, means for signal processing the electric signal output from the photoelectric conversion means, control means for receiving the output signal of the signal processing means and performing desired control,
A plurality of parameter detectors for detecting the operating state of the engine and transmitting to the control means, a controller operated by a control signal of the control means, in which the flame light of the flame light detector is controlled by the plurality of parameters. The first engine operating range (A, B) where dust is likely to adhere to the detection surface and the second engine operating range (C) where the transmittance of flame light due to dust deposition is hardly reduced are determined. In the second engine operating range (C), the control means performs closed-loop control based on the detection signal of the flame detector, and in the first engine operating range (A, B), the control of the flame detector is performed. When the closed loop control by the detection signal is interrupted, the open loop control is performed, and when the second engine operating range (C) is entered from the first engine operating range (A, B), the detection of the flame light detector is performed. signal The closed-loop control with by a predetermined time delay in consideration of the waste incineration attached to the flame light detection surface,
Flame light detection device characterized by starting. 2. The control means according to claim 1, wherein the control means performs ignition timing control by a closed loop in response to a signal indicating a combustion start timing detected by the flame photodetector. Flame light detector. 3. The control means according to claim 1, wherein the control means controls the ignition timing by a closed loop in response to a signal representing the peak timing of combustion detected by the combustion detector. Flame light detector.