JPS6390643A - Air-fuel ratio control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To enhance the accuracy of feedback control from the standpoint of responsiveness and improve the extent of combustibility as well as to make improvements in output, fuel consumption and exhaust performance, by controlling a supply air-fuel ratio so as to cause the spectral distribution of combustion light to become a target pattern. CONSTITUTION:The combustion light transmitted by optical fibers 21a-23a having one end in and around an exhaust valve 16a of each combustion chamber 13a (hereinafter stated to a first cylinder only) of a cylinder head 11 is converted into each spectral signal or electric signals of photoelectric transfer elements 30-32 by way of a band pass-filter 17 (an ultraviolet ray area) 28 (visible ray area) 29 (infrared - near infrared ray areas) via fittings 24-26, and outputted to a control circuit 40 which sets spectral distribution corresponding to a desired air-fuel ratio by each input signal out of various sensors, and performs feedback control over a supply air-fuel ratio so as to cause the spectral distribution of the next time combustion light to become the desired spectral distribution. Therefore, such feedback control that has no responsive delay is carried out, thus combustibility is improved.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is an air-fuel ratio control method for an internal combustion engine that determines the spectral distribution of combustion light in an internal combustion engine such as an automobile, and controls the air-fuel ratio so that this becomes a target pattern. Regarding equipment.

(Prior art) In recent years, with the demand for reduced fuel consumption, purification of exhaust gas, and increased output, the air-fuel ratio is detected by detecting the oxygen concentration in the exhaust gas, and the amount of fuel supplied is adjusted based on this detected information. Feedback control is being performed.

As a conventional air-fuel ratio control device of this type, there is one shown in FIG. In this device, an oxygen sensor 2 provided in the middle of an exhaust manifold 1 detects the oxygen concentration in the exhaust gas, and a control unit 3 determines an air-fuel ratio that is correlated with the oxygen concentration. control unit 3
A signal from the air flow meter 4 and signals from each sensor group indicating other operating conditions are input to the control unit, and the control unit determines whether the air-fuel ratio is within a certain range based on the air-fuel ratio detection information and the signals from each sensor group. The fuel supply amount is controlled so as to output an injection signal to the injector 5 (see Japanese Utility Model Publication No. 12980/1983).

(Problems to be Solved by the Invention) However, in such a conventional air-fuel ratio control device for an internal combustion engine, the amount of air in the exhaust gas discharged from the combustion chamber (i.e., the air-fuel mixture that has already been combusted) is Since the configuration is such that the air-fuel ratio is detected based on the oxygen concentration and the fuel supply amount is controlled based on this detected information, there is room for improvement in terms of feedback control responsiveness.

In other words, when the air-fuel mixture is combusted, the air-fuel ratio of the exhaust air is detected, and the feedback control value for the fuel supply amount is calculated from this detection step, so there is a delay in response from detection to execution of control. For example, in the high rotation range, the target fuel supply ff1 (
In some cases, it may take several tens of combustion strokes to reach the target air-fuel ratio (corresponding to the target air-fuel ratio). In such a case, the accuracy of feedback control for the target value decreases,
Combustion performance deteriorates, leading to reductions in output, fuel efficiency, and exhaust performance.

(Purpose of the Invention) Therefore, the present invention detects the spectral distribution of combustion light generated by combustion and controls the supplied air-fuel ratio so that the spectral distribution becomes a target pattern, thereby improving the accuracy of feedback control from the viewpoint of responsiveness. The aim is to increase fuel efficiency and improve combustion performance, thereby improving output, fuel efficiency, and exhaust performance.

(Means for Solving the Problems) In order to achieve the above object, the air-fuel ratio control device for an internal combustion engine according to the present invention detects light generated within the combustion chamber of the engine, as shown in FIG. a light detection means a,
The spectral discrimination means for discriminating the spectral distribution of combustion light from the output of the light detection means a determines the amount of fuel supplied or inhaled so that the spectral distribution of combustion light follows a predetermined target pattern based on the output of the spectrum discrimination means. It includes a control means C that calculates a control value for controlling the amount of air, and an operation means d that operates the amount of fuel supplied or the amount of intake air based on the output of the control means C.

In the present invention, the spectral distribution of combustion light generated by combustion is detected, and the supplied air-fuel ratio is controlled so that the spectral distribution becomes a target pattern.

Therefore, the accuracy of feedback control is increased in terms of responsiveness, combustion performance is prevented from deteriorating, and output, fuel efficiency, and exhaust performance are improved.

(Example) Hereinafter, the present invention will be explained based on the drawings.

2 to 8 are diagrams showing one embodiment of the present invention.

First, the configuration will be explained. In Figure 2, 11 is 4 in series.
The cylinder head 12 of the cylinder engine is a transmission, and the cylinder head 11 shown in this figure is shown removed from the cylinder block and viewed from below. Intake manifold 148 to cylinder rad 11
One end of 14d is connected to these intake manifolds 1
Injectors 41a to 41d, which will be described later, are arranged at 4a to 14d, respectively. Further, four combustion chambers 13a to 13d are formed in the cylinder head 11, and intake valves 152 to 15d, exhaust valves 16a to 16d, and spark plugs 17a to 17d face each of these combustion chambers 13a to 13d. There is. Note that 18a to 18d are intake boats, and 192 to 19d are exhaust boats.

Each of the combustion chambers 13a to 13d has first, second, and third optical fibers 21a to 2 in the vicinity of the cylinder bore, respectively.
1d, 22a ~ 22b, 23a ~ 23d (
one end of each of the first, second, and
Each of the third optical fibers is connected to the combustion chamber 13 at a portion far from the spark plugs 17a to 17d and near the exhaust valves 16a to 16d.
I am facing a-13d. First, second, and third optical fibers 21a to 21d, 22a to 22b, 23a
-23d detect the light in the combustion chambers 13a-13d and transmit it, and the first optical fibers 21a-21d
The other end is bundled together by a metal fitting 24 and has a wavelength of 200.
It is connected to a bandpass filter 27 that transmits only ultraviolet light of up to 400 nm, and the optical signal output of the bandpass filter 27 is input to a photoelectric conversion element 30 . The other ends of the second optical fibers 22a to 22d are bundled together by a metal fitting 25 and connected to a bandpass filter 28 that transmits only visible light with a wavelength of 400 to 600 nm. The signal output is input to the photoelectric conversion element 31. Further, the third optical fibers 23a to 23d are also connected to the first and second optical fibers 21a to 21d, 2 by means of the metal fittings 26.
Similar to 2a to 22d, they are bundled together and have a wavelength of 600 to 1.
It is connected to a bandpass filter 29 that transmits only red to near-infrared light of 1000 nm, and the optical signal output of the bandpass filter 29 is input to the photoelectric conversion element 32 . In addition, each metal fitting 24, 25, 26, each band pass filter 27, 28
．． 29, (spectrum discrimination means), each photoelectric conversion element 30
．． 31, 32 are each covered by a light shielding case 33, 34, 35, and the light shielding case 33, 34, 35 prevents optical noise from entering the photoelectric conversion element 30, 31, 32.

The first photoelectric conversion element 30 converts the light energy in the ultraviolet region separated from the combustion light by the bandpass filter 27 into an electric signal, and transmits the spectrum signal 1 uv to the control circuit 40.
(control means). On the other hand, the second photoelectric conversion element 3
1 and a third photoelectric conversion element 32 convert optical energy in the visible light range and infrared to near-infrared light range separated from the combustion light into electric signals by a band-pass filter 28 and a third photoelectric conversion element 32, respectively, by a band-pass filter 28 and a band-pass filter 29, respectively. Spectrum signal ■8
1. and outputs them to control circuit i0. The control means 40 receives a spectrum signal ■. s 110% I
Although not shown in the figure, in addition to N, various signals representing the engine speed signal, intake air temperature signal, and other operating conditions are input, and the control circuit 40 determines the target spectral distribution (target air temperature) from the operating conditions. Based on the input spectral signals 1 uv, 8 IN, the fuel supply amount is calculated so that the spectral distribution of combustion light in the next combustion stroke corresponds to this target spectral distribution, and the injector 41a - Outputs an injection signal to 41d (operating means). Injectors 413-41d inject fuel into intake bows 18a-18d connected to intake manifolds 14a-14d based on injection signals.

Next, the effect will be explained.

Figure 3 (a), (b), and (c) are typical mixture concentrations 3
It is a diagram showing the spectral distribution of combustion light when the air-fuel mixture is combusted for each type, and the spectral distribution of the combustion light has characteristics depending on the air-fuel mixture concentration. For example, in the same figure (
Figure a) shows the spectral distribution of combustion light when a lean air-fuel mixture burns, but the light intensity in the red to infrared light range with a wavelength of 600 nm or more is weak, and the light intensity is 300 nm centered around a wavelength of 400 nm.
The light energy is concentrated over ~500 nm. The figure (b) shows the stoichiometric air-fuel ratio, and the figure (c) shows the spectral distribution of combustion light when a rich air-fuel mixture is combusted. FIG. 4 is a diagram showing the relationship between crank angle and light intensity when the combustion light spectral distribution shown in FIG. 3 is separated by bandpass filters 27, 28, and 29 for each wavelength band. In the same figure (a> is the ultraviolet light range (UV: 200-400
The light intensity is the highest when a lean mixture is combusted.

In addition, the same figure (b) shows the visible light range (B-G: 400-600
The figure shows the light intensity in the red to infrared light range (R: 600
The light intensity of ~101000n is the strongest.

In this way, the spectral distribution of combustion light with respect to the air-fuel ratio has a characteristic pattern, and by detecting this pattern, the air-fuel ratio can be determined.

Figure 8 shows the combustion cycle of each cylinder and the bandpass filter 3.
This is a timing chart showing the relationship between each output of 0.31.32, and each cylinder repeats a combustion cycle in the order shown in the figure.

For convenience of explanation, the first cylinder (the leftmost cylinder in FIG. 2) will be taken as an example of the action accompanying the generation of combustion light.

When a spark is ignited by the spark plug 17a in the combustion chamber 13a, the combustion light from the combustion of the air-fuel mixture is transmitted through the optical fiber 21.
a, 22a, 23a to bandpass filters 27, 28, 29, respectively. Only the spectral components corresponding to the passbands of the respective bandpass filters pass through the bandpass filters, and are input to the photoelectric conversion elements 30, 31, and 32. Figures 5 to 7 are diagrams showing each output IuvsIg (8) of the photoelectric conversion element 30, 31, and 32 based on combustion light when changing the air-fuel ratio of the air-fuel mixture by wavelength band. 30.31.
32's output 1 uv, IacsI) (as mentioned above, the signal strength differs depending on the air-fuel ratio of the air-fuel mixture. Now, when the engine is in a partial load operating state and the supplied temperature mixture must be at the stoichiometric air-fuel ratio.

The control circuit 40 controls the outputs of the photoelectric conversion elements 30, 31, and 32 (or their integrated signal strengths) ■uv, ■8
I8 is compared and the ratio uv/IB or I
The fuel supply amount is corrected to increase or decrease so that each value of R/IIG (hereinafter referred to as intensity ratio) is minimized (see FIG. 6(b)). For example, if the outputs of the photoelectric conversion elements 30, 31, and 32 due to the combustion light in the combustion chamber 13a have a pattern as shown in FIG. 5 (combustion light spectral distribution of rare mixture), the intensity ratio T uv/I The value of mG increases, and the control circuit 40 corrects the fuel supply amount to increase until the next combustion cycle. Figure 8 A and H show this effect,
The waveforms of e, f, and g correspond to those shown in FIG. Further, the waveforms of e, f, and g correspond to FIG. 6 (combustion light spectral distribution at the stoichiometric air-fuel ratio). That is,
Combustion of a lean mixture is detected during the expansion stroke of the first cylinder (
(See E-a) The fuel supply amount is corrected to increase so as to reach the stoichiometric air-fuel ratio, and fuel injection is performed at low a (exhaust). Then, as shown in e, f, and g (next combustion cycle), each wavelength becomes a combustion light spectral distribution of the stoichiometric air-fuel ratio. Moreover, if the outputs of the photoelectric conversion elements 30, 31, and 32 due to the combustion light in the combustion chamber 13a have a pattern as shown in FIG. 7 (combustion light spectral distribution of a rich mixture), the intensity ratio ■8/raG becomes larger, and the control circuit 40 corrects the fuel supply amount by one $i amount by the next combustion cycle. On the other hand, when the engine requires output under high load operating conditions, the intensity ratio I uv/I *, I tr
The control circuit 40 increases or decreases the fuel supply amount so that the value of r,/I* becomes the minimum value or a value previously set through experiments with emphasis on output characteristics. For example, the photoelectric conversion elements 30 and 31 are
．． 32 outputs have a pattern as shown in FIG. 5 or FIG. 7, the intensity ratio Iuv/IR1 or I*c/I
, I increases, and the control circuit 40 increases or decreases the fuel supply amount.

The step width of the fuel supply increase/decrease correction described above is appropriately set according to responsiveness and control accuracy.

As described above, in this embodiment, the spectral distribution of combustion light generated by combustion is detected, and the fuel supply amount is corrected to increase or decrease so that the spectral distribution becomes a target pattern, for example, a pattern corresponding to the stoichiometric air-fuel ratio. In this case, the combustion light represents the combustion state during the current combustion cycle, and its detection speed is much faster than conventional detection accuracy based on exhaust oxygen concentration. In other words, the responsiveness is extremely high in terms of air-fuel ratio detection, and it can be said that the timing is approximately the same as combustion (real time). Therefore, since feedback correction of the fuel supply amount is performed based on such detection information at approximately the same timing, there is almost no response delay from detection to execution of control, and only the calculation time in the control system is reduced ( This processing time is actually extremely short since it is based on electrical signals). Therefore, even when operating in a high rotation range, the time to converge to the target value is extremely short.
The accuracy of feedback control for target values is greatly improved. As a result, combustion performance is enhanced, and output, fuel efficiency, and exhaust performance can be improved.

In addition, although the description has been made using the combustion chamber 13a of the first cylinder as an example,
For all combustion chambers 13b to 13d of other cylinders, detection of combustion light and control of fuel supply amount are also performed in the same way.

Furthermore, in this embodiment, a single photoelectric conversion element receives the light transmitted by the optical fiber for each light of the same wavelength in each combustion chamber 13a to 13d, thereby reducing the cost. Even with this configuration, the control circuit 40 determines and controls the ignition timing for each cylinder.
By determining at which timing the optical signal is generated, it is possible to easily determine which cylinder's combustion light causes the optical signal.

Further, in this embodiment, the fuel supply amount is made variable as a method of controlling the air-fuel ratio, but since air is also used as a parameter for the air-fuel ratio, the amount of intake air may be manipulated.

(Effects) According to the present invention, the spectral distribution of combustion light generated by combustion is detected and the fuel supply amount or intake air amount is controlled so that the spectral distribution becomes a predetermined target pattern. It is possible to improve the detection response and improve the accuracy of feedback control, which in turn improves combustion performance and improves output, fuel efficiency, and exhaust performance.

[Brief explanation of the drawing]

FIG. 1 is a basic conceptual diagram of the present invention, FIGS. 2 to 8 are diagrams showing an embodiment of an air-fuel ratio control device for an internal combustion engine according to the present invention, FIG. 2 is an overall configuration diagram thereof, and FIG. is a diagram showing the spectral distribution of the combustion light, Figure 4 is a diagram showing the relationship of light intensity to crank angle for each wavelength band, and Figure 5 is a diagram showing the light intensity at each wavelength when the lean mixture burns. Figure 6 shows the light intensity for each wavelength band when a mixture with the stoichiometric air-fuel ratio burns, and Figure 7 shows the light intensity for each wavelength band when the rich mixture burns. FIG. 8 is a timing chart showing the relationship between the combustion stroke and the output of each bandpass filter, and FIG. 9 is an overall configuration diagram showing a conventional air-fuel ratio control device for an internal combustion engine. 21a ~ 21d, 22a ~ 22d, 23a ~
23d... Optical fiber (light detection means), 27.
28.29... Bandpass filter (spectrum discrimination means), 40... Control circuit (control means), 41a to 41
d...Injector (operating means).

Claims (1)

[Scope of Claims] a) light detection means for detecting light generated in the combustion chamber of an engine; b) spectrum discrimination means for discriminating the spectral distribution of combustion light from the output of the light detection means; c) spectrum discrimination means d) control means for calculating a control value for controlling the amount of fuel supplied or the amount of intake air so that the spectral distribution of combustion light becomes a predetermined target pattern based on the output of the control means; An air-fuel ratio control device for an internal combustion engine, comprising: an operating means for controlling a supply amount or an intake air amount.