JPS6293485A - Combustion light air-fuel ratio sensor - Google Patents

Abstract

PURPOSE:To enable the air-fuel ratio of high accuracy to be detected even in a case that the detection surface of flame light is stained and the transmitted quantity of light is small, by detecting the emission strength of the radical ingredients of the combustion gas of visible radiation range with both light receiving elements, and calculating the air-fuel ratio by these output signal ratios. CONSTITUTION:Combustion flame light introduced from the detection end 3 of the combustion flame light is conducted to an optical fiber cable 4, and is forked therefrom to be conducted to two light catching sensors 5, 6 which are different each other in the emission strength of the CH radical of combustion gas or a spectral sensitivity characteristic. The light receiving elements 5, 6 are connected to a driving process circuit 7 to carry out photoelectric transferring therein, and the signals are conducted to a controller 8 which consists of a microprocessor. In the controller 8, the signals from the driving process circuit 7 are calculated and processed, and the information of an air-fuel ratio is obtained. When the air-fuel ratio is rich, the combustion light is reddish and its wave length is big, and when the air-fuel ratio is lean, the combustion light becomes bluish and its wave length becomes small. Thereby, which wave length ranges of flame become many can be discriminated by taking the ratio of the output signals, so that the judgement of the air-fuel ratio can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a combustion light air-fuel ratio sensor for optically detecting an air-fuel ratio from the state of combustion flame light of an internal combustion engine.

[Background of the Invention] As a method of detecting an air-fuel ratio from combustion flame light in a combustion chamber of an internal combustion engine, there is a method as described in British Patent No. 1,388,384. This method focuses on the fact that the radiation intensity of infrared light from a combustion flame changes depending on the air-fuel ratio, and the peak of the intensity coincides with the stoichiometric air-fuel ratio.

However, this method has the disadvantage that the light intensity changes due to dirt or the like on the flame light detection surface, making it impossible to obtain sufficient air-fuel ratio detection accuracy. Furthermore, since the output characteristic with the peak at the stoichiometric air-fuel ratio becomes a binary characteristic, there is a problem in that processing becomes complicated.

[Purpose of the invention]

The aim of the present invention is to solve the problem of the conventional technology described above, which is an increase in the air-fuel ratio detection error due to dirt on the combustion flame light detection surface, and an increase in the binary characteristic due to the output characteristic with the peak of the stoichiometric air-fuel ratio. Both problems are solved and a signal proportional to the air-fuel ratio is created by 1. An object of the present invention is to provide a combustion optical air-fuel ratio sensor that always outputs stably regardless of the amount of dirt on a detection surface.

[Summary of the invention]

The present invention focuses on the fact that the color of combustion flame in the visible light range changes depending on the air-fuel ratio, and detects the emission intensity of the radical component (C2+ CH+0TT) of the combustion gas in the visible light range with a light receiving element, We devised a method for determining the air-fuel ratio from these intensity ratios, that is, the output signal ratios. By this method, the air-fuel ratio can be detected with high accuracy even when the flame light detection surface is dirty and the amount of transmitted flame light is small, and a practical combustion light air-fuel ratio sensor can be constructed.

[Embodiments of the invention]

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

FIG. 1 shows the overall configuration of an engine control device using a combustion optical air-fuel ratio sensor according to the present invention. A combustion flame light detection end 3 is installed to open into the combustion chamber 2 of the engine 1, and is integrated with a spark plug. In this embodiment, in the case of a plurality of lower engine engines, it is assumed that only one representative cylinder is provided with the flame light detection end 3.

The combustion flame light led out by this combustion flame light detection end 3 is guided to an optical fiber cable 4, branched into two, and guided to two light receiving elements 5 and 6 having different spectral sensitivities. The light receiving element 5.6 is connected to a drive processing circuit 7, where photoelectric conversion is performed, and the signal is guided to a controller 8 consisting of a microcomputer. The controller 8 includes an air flow meter 9. Various engine information signals such as an opening sensor for the throttle valve 10, a crank angle sensor 11, and a water temperature sensor 12 are manually generated. controller 8
Then, the two signals from the drive processing circuit 7 are processed to obtain information on the air-fuel ratio. Then, the ignition timing is determined for optimum fuel injection based on the various operating information signals and the air-fuel ratio multiplied by 1), and the control signal is sent to the fuel injection valve 13 and the ignition timing control device 14. In the fuel injection valve 3, the valve opening time is controlled by the control signal, and the amount of fuel injected is measured. -・5 The ignition timing control device 14 uses the control signal to plug the ignition plug; (
The supply timing of the high voltage applied to the is adjusted and sent out. Although a multi-point fuel injection system is shown here as an example, a single-point fuel injection system, a carburetor type, etc. can be similarly configured.

FIG. 2 is a detailed view of the combustion flame light detection end 3, which has a diameter of about 1 mm for guiding the combustion flame light. A quartz glass fiber 15 of AWU is disposed so as to pass through the central axis of the spark plug. That is, the central shaft portions of the center electrode 16 and the high voltage terminal shaft 17 are opened, and the quartz glass fiber 15 is inserted therein.
To fix these three parts and the insulator 18 and maintain airtightness, put the copper-containing glass sealing material 19 as shown in Fig. 2, heat it in a heating furnace, and when it becomes molten, press the high voltage terminal 17 downward from the side. The material was sealed by allowing it to flow into the gaps between parts. The flame light detection surface 15a is configured in a spherical or conical shape so as to capture light from the entire area of the combustion chamber, thereby making it possible to detect the average air-fuel ratio within the combustion chamber. Note that a normal spark plug is sufficient as the plug body 20, and a side electrode 21 attached to the tip thereof is also the same.

FIG. 3 is an example of a detailed diagram of the optical transmission system from the combustion flame light detection end 3 to the light receiving element 5.6. A quartz fiber portion of the combustion flame light detection end 3 on the side opposite to the combustion chamber is connected to a bundle fiber 23 by a connector 22. In addition, this =1 connector 22 and the high voltage terminal 2 are fixed inside the body.
4 is installed. This is just an example; as is well known, optical fiber is electrically non-inductive, so it is possible to combine the high-voltage coat of the spark plug with the bundle fiber, depending on the application. All you have to do is decide how to configure it. The bundle fiber 23 for guiding the combustion flame light to the light-receiving elements 5 and 6 is, as is well known, a bundle of several to several dozen fibers bound together with a covering material 25 (cross section A). Diameter 250 μm (core diameter 22
Nineteen multi-component glass fibers each having a diameter of 0 μm and a cladding diameter of 250 μm are bundled together and have an outer diameter of approximately 1.2+nm PA degree, which is approximately the same as the diameter of the quartz fiber. By aligning the diameters in this way, loss at the joint is minimized. This bundle fiber is branched at the branching part 27 to form 10 glass fibers and 1) bundle fiber as shown in the cross sections 13 and C, and the combustion flame light is transmitted to the light receiving elements 5 and 6 via the connectors 28 and 2n. The structure is designed to guide

What talent? In place of the bundle fiber 23, a normal phosphor cored fiber may be used, but in that case, an optical splitter is installed at the rear end of the cored fiber to guide the flame light to each light receiving element.

FIG. 4 shows the spectral sensitivities a and b of the light receiving elements 5 and 6. The light receiving element 5 has a peak around 430 nm, which corresponds to the emission wavelength of CTT radicals in the combustion gas, 432. n
m, and the emission intensity of this CH radical is detected.

Further, the light receiving element 6 detects the C2 radical emission intensity, which has a peak near 520 nm, which is close to the C2 radical emission wavelength of 51.6 nm. Such a light-receiving element can be easily realized by using a photodiode for color detection, a so-called color sensor, for blue detection (equivalent to A characteristic) and for green detection (equivalent to B characteristic).

As shown in Figure 5, such light-receiving elements generally have the characteristic that the output signal changes depending on the illuminance, and the flame light changes as the engine operating condition changes and the combustion condition changes. It becomes necessary to correct illuminance changes by some method.

To this end, in the present invention, the ratio of the output signals of the light receiving elements 5 and 6 is determined. In other words, as mentioned above, when the air-fuel ratio is rich, the combustion flame becomes reddish (larger wavelength), and when the air-fuel ratio becomes leaner, it becomes bluerish (smaller wavelength), so the ratio of the above output signals should be taken. This makes it possible to determine which wavelength band the number of flames is increasing, and to infer the air-fuel ratio.

The sixth sentence shows the drive processing circuit M7 for the light receiving elements 5 and 6, the microcomputer 35 in the controller 8, and the A/D converter 34. Signal amplification is performed by arranging a plurality of resistors as shown in the figure to form a circuit '4. The operational amplifier used here is of a dual power supply type, and the output signal changes in voltage level from - to 10. The analog output voltage obtained here is peak hold circuit 32°33
The signal is led to the A/D inverter 34 via the A/D inverter 34, converted into a digital signal, and then input to the microcomputer 35, where arithmetic processing is executed to obtain an air-fuel ratio signal from the ratio of both signals. The control tie chart of FIG. 6 is shown in FIG. A peak of signal S6,85 occurs.

Therefore, this is held by the peak hold circuit 33.32 (dotted line in Fig. 7, 86.S5), and further
], Sampling pulses SPi and SP2 (given from the microcomputer 35 to the AID converter 34) delayed from 1 by the crank angle fix and θ2 are taken into the A/D converter 34, where they are converted into digital signals, and then the microcomputer Computer; 35
The calculation of the ratio between the two is executed to obtain the air-fuel ratio. Note that each output signal 86. The hold value of S5 is top dead center Sl
The command Ml from the microcomputer 35 at the crank angle Oδ (01, larger than θ2, several degrees to several tens of degrees) from l.
, Mx.

Incidentally, the peak values of the output signals S5 and S6 from the light receiving elements 5 and 6 vary every cycle. This is because the air-fuel ratio of the metal mixture supplied to the engine combustion chamber changes every cycle! ! This is because the air-fuel ratio signal remains at 1+t.If closed-loop control of the fuel amount is executed each time based on the air-fuel ratio signal for each cycle, there is a risk that the control system will become unstable with even more fluctuations. Therefore, if the output signals of segment i cycle are written as 85 (i) and 86 (i), then
At the time of the nth cycle, V+s = (85(n) +85 (n-1) 10-
+85 (n-N+1))/N-(1)Vs = (8
6(n) +86 (n-1) 10-+86 (n-N
+1) ) /11... Average value VI of N times as shown in (2)! , Ve are determined, and the air-fuel ratio is determined from the ratio of the two to perform control.

FIG. 8 thus shows the above VFI with respect to the air-fuel ratio.

This is the result of finding v6, and both are the theoretical air-fuel ratio A/F=
The output is highest near 14.7, and the output tends to be smaller even if it is darker or thinner than that. This is due to the fact that the illuminance of the combustion flame itself becomes smaller as the area becomes darker and as the area becomes thinner. Therefore, the ratio between the two is r = Ve/Ve
...When (3) is determined, the characteristics shown in FIG. 9 are obtained. That is, in the dark region (old Ch), the emission intensity of C2 radicals (5]6 nm) is greater than that of OH radicals (432 nm) (the flame becomes reddish), and the ratio r becomes large. On the other hand, in the thin air-fuel ratio region (1, θan), 'C
As the light emission intensity of can. Therefore, by storing the characteristics shown in FIG. 9 in advance in the microcomputer 35 as a function or as a map value, the signal of the air-fuel ratio A/F can be obtained from the value of r. Also, A/
If the absolute value of F is not required, the value of r itself may be used to perform deviation correction control from a predetermined set value.

In the above embodiment, only one fuel-dawn optical air-fuel ratio sensor is attached to the representative cylinder, but this sensor is installed in each cylinder to detect the air-fuel ratio of each cylinder, and to detect the air-fuel ratio of each cylinder. By controlling the air-fuel ratio, it becomes possible to control the air-fuel ratio more precisely. However, with this configuration, for example, in the case of a 4-cylinder engine, 2 x 4-8 light receiving elements are required, and 2 bundle fibers are required.
Four branches are required. Furthermore, if other information (knock signal, combustion start timing signal) is to be extracted at the same time, the number of fibers and the number of light-receiving elements will further increase, which will make the system more complicated and will also result in an increase in varnish. FIG. 10 shows an embodiment for solving these problems, in which light is guided from the flame photodetector 3A-3n of each cylinder to the optical coupler 48 through optical fibers 4Δ to -'ID. , where 4
Combine books. In the case of a four-cycle engine, about 3/4 is dark field, and the explosion stroke (bright field) alternates between each cylinder, so even if you combine each cylinder into one in this way, the signal of any cylinder will be different. This can be easily determined after it is converted into a low voltage signal. The optical signals combined by the optical coupler 48 are then guided to an optical splitter 49 and branched into the required number of optical paths. Fig. 10 shows what is transmitted to the light receiving elements 50 and 51 for air-fuel ratio detection, and the light receiving element 52 for knock and combustion start timing detection.
It is divided into what is transmitted and what is transmitted. The broken line portion 53 can be made into a more compact structure by forming it into an optical module. According to this embodiment, the number of optical fibers and light receiving elements can be saved when detecting the air-fuel ratio and the knock signal in each cylinder in a multi-cylinder engine.

In addition, in the following I-I, the air-fuel ratio is detected using 02 radicals and C
This was done based on the intensity of the emission waves of II radicals, but
Almost similar results were obtained even if this was done by measuring CI-T radicals and OH radicals in the same way, and Cx,
C) T, OT■ If all of each radical is used, detection accuracy can be further improved.

〔Effect of the invention〕

As described above, according to the present invention, even when the detection surface of the combustion flame light detection end is contaminated with carbon etc. and the amount of transmitted light is reduced, the ratio of the amount of light of each wavelength hardly changes, so the influence of the dirt The effect is that the air-fuel ratio can be detected without being affected by
Also, unlike conventional air-fuel ratio sensors installed in the exhaust pipe, it can be attached to each cylinder to control the air-fuel ratio for each cylinder without a large delay time, improving high-speed control, exhaust purification, fuel efficiency reduction, and other drivability improvements. be measured. Furthermore, since the detected value and the air-fuel ratio have a monotonous one-to-one characteristic, an accurate value of the air-fuel ratio is not required for control, and the ratio r obtained by calculation can be used as is, and the control system processing It also has the effect of reducing the amount.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram of an engine control device using the combustion light air-fuel ratio sensor according to the present invention, Fig. 2 is a structural diagram of the combustion flame light detection end, and Fig. 3 is a photoelectric conversion section from the combustion flame light detection end. Figure 4 is a diagram of the spectral sensitivity of the light-receiving element, Figure 5 is its characteristic diagram with respect to illuminance, Figure 6 is a circuit configuration diagram of the photoelectric conversion signal processing unit, and Figure 7 is a detailed diagram of the optical transmission section up to The time chart, Figure 8 is a diagram showing the relationship between the air-fuel ratio and the average light-receiving element output value, Figure 9 is a diagram showing the relationship between the air-fuel ratio and the ratio of the light-receiving element output, and Figure 10 is the air-fuel ratio of multiple cylinders. FIG. 6 shows another embodiment of the invention suitable for detection. 3... Combustion flame light detection end, 5, 6... Light receiving element, 7
...Start-up processing circuit, 8...Controller.

Claims (1)

[Claims] 1. A combustion flame light detection end for guiding combustion flame light from the combustion chamber of an internal combustion engine to the outside, a light branching means for branching the flame light derived from the detection end into a plurality of parts, and a light branching means for branching the flame light derived from the detection end into a plurality of pieces, A light receiving means having different spectral sensitivities for converting each flame light into an electric signal, detecting the peak value of each output electric signal of the light receiving means, and further detecting an air-fuel ratio signal from the ratio of these peak values. 1. A combustion optical air-fuel ratio sensor comprising: arithmetic processing means for calculating.