EP0632864B1 - Arrangement for determining the parameters of an internal combustion engine - Google Patents

Abstract

An arrangement for determining the parameters of an internal combustion engine, in particular an Otto engine operating with gaseous fuels, has at least one optical sensor for observing the emission of light caused by the combustion in a combustion chamber of the internal combustion engine and at least one photodetector for converting the light emitted into electric signals which are processed in an evaluation unit. In order to achieve a rapid and accurate regulation, the evaluation unit (11) has an arrangement (15) for determining the maximum or mean intensity of the light emitted during each combustion cycle on the basis of the corresponding electric signal. The evaluation unit (11) further has a regulating unit (17) which regulates at least one engine parameter depending on the intensity maxima.

Description

The invention relates to a device for controlling engine parameters, in particular the ignition timing or the fuel-air ratio of an internal combustion engine, in particular a gasoline engine operated with gaseous fuels, with at least one optical sensor for observing the light emission caused by the combustion in a combustion chamber of the internal combustion engine and with at least one photodetector for converting the light emission into electrical signals, which are processed in an evaluation device.

It has already been proposed to use the light emission caused by the combustion in a combustion chamber in order to regulate engine parameters. The light is led out of the engine via an optical pickup, which is attached to the engine and generally a light-guiding element leading into the combustion chamber (in the simplest case a so-called combustion chamber window), without disturbing the other combustion processes. The optical pickup can also be integrated in the spark plug.

So far, a control signal for controlling the ignition timing has mainly been obtained from the position of the light emission over time.

A control device for a motor is known from DE-OS 35 05 063, in which the difference between the maximum value of the light intensity and an average value formed from a plurality of maximum values represents the controlled variable. When this difference is formed, the information about the absolute value of the maximum value is lost. The known control device ultimately serves to control the uneven running of the engine. With which engine parameters, in particular with which fuel-air ratio (lambda) the desired smoothness is achieved, is irrelevant there. There is therefore no regulation of a specific fuel-air ratio.

The object of the invention is to provide a device of the type mentioned at the beginning with which it is possible to precisely control at least one engine parameter.

According to the invention, this is achieved in a device of the type mentioned at the outset in that the evaluation device comprises a device for determining the absolute value of the maximum of the light emission of each combustion cycle in the corresponding electrical signal and provides an output signal reflecting the absolute value of the maximum and in that the evaluation device furthermore contains a control unit comprises, which controls at least one motor parameter as a function of the output signal reflecting the absolute value of the maximum.

While the position of the light emission has been evaluated over time in the known proposals (for example US Pat. No. 4,381,748), it is proposed according to the invention to use the height of the intensity maximum of the light emission in order to detect a motor parameter and to regulate motor parameters via a control unit . Such an engine parameter is, in particular, the fuel-air ratio (lambda). However, other engine parameters such as the ignition timing, the boost pressure, the engine temperature etc. can also be regulated in principle as a function of the intensity maximum of the intensity of the light emission of each combustion cycle. The maximum of the light emission, which is reflected in the electrical signal of the photodetector, can easily be determined by an electronic evaluation device and fed to the actual value input of a control device which then adjusts or regulates at least one motor parameter as a function thereof.

In order to smooth fluctuations in the light emission in individual successive combustion cycles, it is expedient if the device for determining the intensity maximum is followed by an averager which emits a signal corresponding to the mean value from the intensity maxima of a predeterminable number of combustion cycles, and that the output of the averager with the Actual value input of the control unit is connected. The maximum intensity can be averaged over 20 to 100 cycles, for example.

A further preferred embodiment is characterized in that the evaluation device has a device for detecting misfires, which on the one hand receives signals related to the light emission and on the other hand signals which are dependent on a sensor from the crankshaft angle or the piston position of the engine and which in the case of an electrical signal is below Threshold value delivers an output signal at its output at a point in time or time window in which ignition is normally dependent on the crankshaft angle or on the piston position. The signals emitted by the device for detecting misfires can, for example, be counted and, in the case of a certain number or frequency of misfires, can cause an emergency shutdown of the engine.

It is also possible to also supply the signals from the device for detecting misfires to the averager. In order to avoid falsified averages, this can simply ignore combustion cycles with misfires in the averaging.

It has been shown in particular in the investigation of gas engines that the radicals formed during the ignition emit light in a certain frequency range, especially in the ultraviolet range (approx. 200 nm to 350 nm). By means of an optical bandpass filter, which is preferably connected upstream of the photodetector, one can now specifically evaluate a specific spectral range, a so-called spectral window, and use the maximum light emission occurring in this spectral window to regulate engine parameters. In the case of a gas engine, it has been found that the intensity of the radiation in the UV region is strongly dependent on the combustion gas / air ratio, a higher intensity occurring with smaller lambda values. This can be used to achieve lambda control based on the light intensity of the UV emission. At the same time, it is of course also possible to regulate other engine parameters, for example the ignition timing based on the light emission of each combustion cycle.

From a constructional point of view, it is particularly advantageous if a bandpass filter, preferably a colored glass filter, is arranged in or on the optical pickup, it being possible, for example, by using specially doped types of glass, that the light from the combustion chamber, which leads to the outside, itself has bandpass filtering properties, and thus can form a bandpass filter per combustion chamber if desired.

Another advantageous embodiment of the invention is that in a multi-cylinder internal combustion engine for cylinder-selective control of the engine parameters, an optical pickup is arranged on the combustion chamber of each cylinder, each with its own photodetector and its own evaluation device belongs to a control unit which controls the engine parameters of the respective cylinder as a function of the electrical signals corresponding to the light emission of the respective cylinder and adjustable setpoints. The cylinder-selective control of engine parameters, for example the fuel-air ratio for each cylinder individually, allows more precise control and operation of the engine. In principle, it is of course also conceivable and possible to control one or more engine parameters for several combustion chambers simultaneously, depending on the light emission of at least one combustion chamber.

Further advantages and details of the invention are explained in more detail in the following description of the figures.

Fig. 1

einen schematischen Querschnitt durch den Zylinderkopfbereich eines Zylinders mit eingesetztem optischem Aufnehmer,

Fig. 2

in einem Blockdiagramm die Auswerteinrichtung für ein Ausführungsbeispiel der Erfindung und

Fig. 3

schematisch einen mehrzylindrigen Verbrennungsmotor mit einer zylinderselektiven Verbrennungsgas-Luft-Gemisch-Regelung in Abhängigkeit von der Lichtemission aus den einzelnen Brennräumen.

Fig. 4

eine Selbstkalibrierungsvorrichtung in einem Blockdiagramm

Show it:

Fig. 1

2 shows a schematic cross section through the cylinder head region of a cylinder with an optical pickup inserted,

Fig. 2

in a block diagram the evaluation device for an embodiment of the invention and

Fig. 3

schematically a multi-cylinder internal combustion engine with a cylinder-selective combustion gas-air mixture control depending on the light emission from the individual combustion chambers.

Fig. 4

a self-calibration device in a block diagram

The optical transducer (probe), designated overall by 1, is inserted in the cylinder head 7 of a cylinder of an internal combustion engine and held by means of a union nut 3. The optical pickup 1 comprises a light-conducting glass rod 2, which extends into the combustion chamber 9 above the piston 8. In addition, the optical pickup comprises an optical waveguide plug adapter 4, which makes it possible to detachably connect an optical waveguide to the outer end of the glass rod 2, in particular in the form of a flexible optical fiber 6, via an optical waveguide plug 5. All that is required is to plug the optical fiber connector 5 in the direction of arrow 10 into the optical fiber connector adapter 4. It is thus possible for the light which is produced in the combustion chamber 9 during combustion to be fed first to the evaluation device via the glass rod 2 and then via the flexible optical fiber 6. The flexible optical fiber allows the electronic evaluation device to be installed remotely and can be easily replaced in the event of damage.

2 is an exemplary embodiment of such an evaluation device 11. The light detected by an optical pickup 1 from a combustion chamber is fed to the electronic evaluation device 11 via an optical fiber 6 (for example, which is particularly transparent to the UV range). The optical fiber 6 can also be detachably connected to the evaluation device. At the input of the evaluation device, a photodetector 12 (for example a UV photodiode with a spectral sensitivity range from 185 to 1150 nm) converts the light into electrical signals, which are then amplified in an amplifier 13 and filtered in a high-pass or band-pass filter 14. The electrical signals corresponding to the light emission are then passed by a device 15 for determining the intensity maximum of the light emission of each combustion cycle. The output signal present on line 16 thus reflects the intensity maximum of the light emission every combustion cycle again, for example a high-pass filter or a band-pass filter can be integrated in the optical pickup in order to observe only a spectral window. The filter can be formed by the glass rod 2, which consists of special glass. However, it is also possible to use a separate filter element. Measurements have shown, among other things, that the radicals formed during the ignition emit light in the ultraviolet range (approx. 200 nm to 350 nm). The intensity of this radiation is very much dependent on the lambda (high intensity with a small lambda). A relatively precise lambda control can thus be implemented on the basis of the light intensity of the UV emission. Knocking can also be detected by means of UV emission.

The same applies to the wavelengths around 600 nm (solid-state emitters), whereby these wavelengths are much easier to transmit and detect. Knock detection is, however, more difficult at these wavelengths, since the solids remain after knocking and the higher-frequency knock information is therefore partially lost. As a compromise, it is beneficial to effectively observe a wavelength window of approximately 185 to 600 nm. Since the UV photodiode is already insensitive below 185 nm, an optical high-pass filter is sufficient, which is only permeable for wavelengths below 600 nm.

In principle, the signal present on line 16 could be fed to the control unit 17, which then controls an engine parameter (for example the fuel / air ratio) via an output amplifier 18 and an engine parameter adjustment device (for example a mixture adjustment device 19). To avoid fluctuations in the individual combustion cycles smoothing, it is more favorable if the output signals on line 16 are averaged over a number of, for example, 10 to 100 cycles, for example 30 cycles, that is to say the average of the intensity maxima is determined over a predeterminable number of combustion cycles. This takes place in the mean value generator 18, the output 19 of which is connected to the actual value input 20 of the control unit 17.

The probe drift (e.g. due to contamination of the combustion chamber probe) can be compensated for by a self-calibration device which, for example, acts on an additional input 36 of the amplifier 14 for drift correction. With this device, the contamination can be determined during engine operation and a respective correction signal can be generated (FIG. 4).

A light pulse is fed into the optical waveguide by the self-calibration device 37 under angle mark control. This light pulse continues via the optical waveguide 6 and the combustion chamber window 6 into the combustion chamber, from where it is reflected. The reflected pulse then returns to the self-calibration device 37. The intensity of the reflected pulse is a measure of the contamination of the combustion chamber window. With this size can then For example, the evaluation device can be tracked (input 36). The self-calibration process is started by the self-calibration trigger device 38 whenever no combustion is taking place (e.g. change TDC or during compression). This is the same combustion chamber window and the same optical waveguide as in the evaluation unit described above. The evaluation device and the self-calibration device are decoupled via optics.

In addition, a device 21 for detecting misfires is provided in FIG. 2, which receives signals related to the light emission on the one hand via line 16 and signals dependent on the crankshaft angle or the piston bearing of the engine on the other hand via a sensor 22. Sensors for detecting the crankshaft angle or the piston bearings of the engine are well known to the person skilled in the art and do not need to be described here in more detail. They generally emit a certain trigger signal at a certain motor position. The device 21 for detecting misfires now checks whether light emission occurs in a certain time window, which is determined by the trigger signal from the sensor 22. This should normally be the case if the ignition is successful. If this is not the case, it outputs a corresponding signal at its output 23, which indicates a misfire. This signal can be supplied to a logic block "inhibit" in the averager 18, which causes those combustion cycles in which combustion misfires occur to be disregarded when averaging. This means that there is no falsification of the mean value for individual misfires.

Misfires can also be communicated via line 34 to the emergency shutdown device 35, which, however, switches off the engine at a certain frequency of misfires.

The part of the evaluation device essentially comprising parts 1, 6, 12, 13, 14, 15 (and possibly 18) represents an "optical lambda probe" which, depending on the absolute value of the fuel-air ratio, has a corresponding analog signal at the output 19 supplies. Such a lambda probe can also be marketed and used independently of the following control unit. However, it is of course also possible to implement the electrical components of the lambda probe and the control unit 17 together.

The control unit 17 comprises a setpoint generator 25, via which the desired setpoint of the motor parameter can be set. A control difference xd results from the comparison of the set value w with the actual value x (intensity maximum averaged over several cycles in a spectral window). This is fed to stage 26, which then emits an actuating signal for regulating an engine parameter at its output. The control loop is thus closed.

In stage 14, as indicated by broken lines 28, control differences xd of several optical pickups 1 can be connected. This level then takes, for example, the largest value of all connected control differences for the calculation of the manipulated variable y. For example, in a multi-cylinder internal combustion engine that is only equipped with a single gas lift mixer, the combustion gas / air ratio can be regulated as a function of the light emission in all cylinders.

However, cylinder-selective control is also conceivable and inexpensive, as is shown, for example, in FIG. 3. A five-cylinder internal combustion engine 29 is shown there as an example. The optical pickups 1 extend into the combustion chamber of each cylinder and are each connected to the electronic evaluation device 11 'via flexible optical fibers 6. This electronic evaluation device 11 'essentially comprises five evaluation devices 11, as shown in FIG. 2. Each of these evaluation devices 11 receives, via a line 30, a signal determined by a sensor 31, which indicates the crankshaft angle. A cylinder-selective control of engine parameters takes place via the evaluation devices 11, in the embodiment of the combustion gas-air ratio of each individual cylinder shown in FIG. 3. For this purpose, a control line 32 leads from each evaluation device 11 to the individual adjusting devices 33 for the combustion gas / air ratio. With this device it is therefore possible to regulate certain engine parameters in a cylinder-selective manner as a function of the light emission of each combustion cycle.

Claims (20)

1. Apparatus for controlling engine parameters, in particular the ignition timing or the fuel-air ratio of an internal combustion engine, in particular of a four stroke engine driven by gaseous fuels, with at least one optical sensor (1) for observing the light emission caused by combustion in a combustion chamber of an internal combustion engine, and with at least one photo-sensor (12) for converting the light emission into electrical signals, which are processed in an evaluation apparatus (11), characterised in that the evaluation apparatus (11) includes an apparatus (15) for determining the absolute value of the maximum of the light emission of each combustion cycle from the corresponding electrical signal and delivering an output signal reflecting the absolute value of the maximum, and that the evaluation apparatus (11) further includes a control unit which controls at least one engine parameter dependent upon the output signal reflecting the absolute value of the maximum.
2. Apparatus according to claim 1, characterised in that the apparatus (15) for sensing the maximum is connected on the output side to an averaging device (18) which supplies a signal corresponding to the average value of the maxima of intensity of a predeterminable number of combustion cycles, wherein the output (19) of the averaging device (18) is connected to the actual value input (20) of the control unit (17).
3. Apparatus according to claim 1 or 2, characterised in that the evaluation apparatus is provided with an apparatus (21) for sensing combustion misfires, which receives on the one hand signals connected with the light emission and on the other hand signals from a sensor (22) dependent upon the crankshaft angle and the position of the pistons in the engine, and which, when there is an electrical signal below a threshold at a point in time or in a time window dependent upon the crankshaft angle or the position of the pistons, during which ignition normally takes place, delivers an output signal at its output (23).
4. Apparatus according to claim 2 and 3, characterised in that the output (23) of the apparatus (21) for sensing combustion misfires is connected to the averaging device (18), and the averaging device (18) is configured so that it does not take into account combustion cycles with combustion misfires in the averaging process.
5. Apparatus according to claim 3 or 4, characterised in that the output (23) of the apparatus (21) for sensing combustion misfires is connected to an emergency shut-off system (35) which acts to stop the internal combustion engine after a specified number or a specified frequency of misfires.
6. Apparatus according to one of claims 1 to 5, characterised in that an optical filter (2), preferably a high-pass filter, is connected on the input side to the photo-sensor (1).
7. Apparatus according to claim 6, characterised in that the filtering characteristic of the filter and the sensitivity range of the photo-sensor are selected so that there is an observation window with a suitable wave-length, also in the UV region.
8. Apparatus according to claim 6 or 7, characterised in that the wave length range sensed is between 150 and 650 nm.
9. Apparatus according to one of claims 1 to 8, characterised in that between the optical sensor (1) on the engine (29) and the evaluation apparatus (11), at least one flexible optical fibre (6) is arranged.
10. Apparatus according to one of claims 6 to 9, characterised in that in or on the optical sensor (1) an optical filter, preferably a coloured glass filter (2) is arranged.
11. Apparatus according to claim 10, characterised in that the material conducting the light from the combustion chamber, preferably glass, itself has band pass filtering properties and preferably forms the only optical band pass filter per combustion chamber.
12. Apparatus according to one of claims 1 to 11, characterised in that in the case of a multi-cylinder internal combustion engine (29), on the combustion chamber (9) of each cylinder an optical sensor (1) is arranged for cylinder-selective control of the engine parameters, to each of which a separate photo-sensor and evaluation apparatus (11) belongs, with a control unit, which controls the engine parameters of respective cylinder depending on the electrical signals corresponding to the light emission of the respective cylinder, and adjustable set-values.
13. Apparatus according to claim 12, characterised in that a common apparatus (31) for sensing the crankshaft angle or position of the pistons is provided for all the evaluation apparatus (11).
14. Apparatus according to one of claims 1 to 13, characterised in that a mixture adjusting device (19, 33) is provided, by means of which the composition of the fuel-air mixture supplied to the internal combustion engine is controllable, dependent upon the light emission in the combustion chamber.
15. Apparatus according to one of claims 1 to 14, characterised in that, for calibration of the optical sensor in an internal combustion engine, a light source which transmits light to the sensor, and further a sensing apparatus for sensing the portion of light returning from the sensor are provided.
16. Apparatus according to claim 15, characterised in that the light is transmitted to the sensor when it receives no measured light, for example arising from combustion in the combustion chamber.
17. Apparatus according to claim 15 or 16, characterised in that the light source (37) is arranged outside the combustion chamber (9).
18. Apparatus according to claim 17, characterised in that the light source (37) is connected to the optical sensor (1) by means of an optical fibre (6).
19. Device according to one of claims 15 to 18, characterised in that the sensing apparatus sensing the reflected light of the light source supplies a correction signal to the processing apparatus (11) dependent upon the reflected light intensity sensed.
20. Apparatus according to one of claims 1 to 19, characterised in that the optical sensor (1) extends into the main combustion chamber (9) of the internal combustion engine lying directly above the piston (8).

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