EP0191167A2 - Method and apparatus for the regulation of the combustions in the combustion chambers of a combustion engine - Google Patents

Abstract

In the method/device, the delayed combustions in the combustion chambers of the engine are detected and the combustions are regulated as a function thereof. In the illustrative embodiment described, the light intensity in the combustion chambers is used for the detection of the delayed combustions and this signal is conditioned in appropriate fashion in order, finally, to influence the quantity of fuel fed to the engine. A particularly advantageous further development illustrated is a so-called categorisation, with the aid of which the actual control is only supplied with a stepped input signal. Overall it is possible, with the aid of the method/device, on the one hand to increase the smoothness of running of an internal combustion engine but, on the other hand, simultaneously to operate the said engine at its running limit. <IMAGE>

Description

State of the art

The invention is a method and a device for controlling the combustion in the combustion chambers of an internal combustion engine according to the preamble of the main claims.

From German patent application P 31 11 135 it is known to use optical sensors to detect the light signals in the combustion chamber of an internal combustion engine during a combustion process. Using special precautions, it is possible to infer characteristic points of the combustion process from the course of the light intensity of the light resulting from the combustion. The characteristic points can then be assigned to the corresponding crankshaft angles by means of further sensors, for example a reference mark sensor. By specifying the target crankshaft angle and comparing it with the light signal-dependent actual crankshaft angles, a re gel circuit for controlling, for example, the ignition timing or other variables influencing the combustion. With the aid of the described device, it is generally possible to regulate an internal combustion engine to almost optimum values with a view to smooth running as much as possible.

The disadvantage of the described device, however, is that the control system also intervenes when the smooth running can basically no longer be improved. This is a consequence of the fact that the control described does not differentiate between light signals that indicate good burns and light signals that indicate carried-over burns. With regard to the light signals, no distinction is made between burns that cause uneven running or those that do not result in uneven running.

Advantages of the invention

The method according to the invention and the device according to the invention for controlling the burns in the combustion chambers of an internal combustion engine with the features of the two main claims has the advantage over the prior art described that only those burns are taken into account which have a negative influence on the smooth running of the internal combustion engine .

This is achieved in that, in a first step, burns carried over from the combustion chambers are detected, for example with the aid of the intensities of the light signals, and in a second step, only with the aid of the burns carried over, the burns in the combustion chambers of the Internal combustion engine can be influenced with a view to reducing the carried-over combustion.

It is particularly advantageous to control the internal combustion engine with the aid of the maximum values of the light intensities. It is also particularly advantageous not to control the actual regulation with a linear signal, but to divide this linear signal into individual classes in order to then carry out the regulation with the classified, step-shaped signal.

Further advantageous developments and improvements of the method or the device specified in the main claims are possible through the measures listed in the subclaims.

drawing

Embodiments of the invention are shown in the drawing and explained in more detail in the following description. 1 shows a diagram of the indicated mean pressures in the combustion chambers of the internal combustion engine, FIG. 2 shows a diagram of the radiation maxima of the light intensities in the combustion chambers of the internal combustion engine, FIG. 3 shows a relationship between the induced mean pressures and the radiation maxima, FIG. 4 shows an exemplary embodiment of a control system, and FIG 5 shows an exemplary embodiment of a classification.

Description of the embodiments

The exemplary embodiments described below involve the control of the burns in the Combustion chambers of an internal combustion engine. The exemplary embodiments are explained in connection with gasoline internal combustion engines, but this does not mean that the inventive idea on which the exemplary embodiments are based could not also be applied to other internal combustion engine types. Likewise, the exemplary embodiments described below are not restricted to special circuit-related implementations, but can be implemented in any embodiment known to the person skilled in the art. It is therefore possible to implement the inventive idea on which the exemplary embodiments are based in the form of analog circuits, digital circuits, with the aid of appropriately programmed computing devices, in the form of combinations of these options, etc., in a corresponding object according to the invention.

FIG. 1 shows a diagram of the indicated mean pressures in the combustion chambers of the internal combustion engine. On the abscissa of the diagram, the crankshaft angle after top dead center is plotted in degrees, on the ordinate, on the other hand, the indicated mean pressure PI related to a mean indicated mean pressure PIQ. The indicated mean pressure PI is understood to mean an average pressure level in a combustion chamber of the internal combustion engine, which during the period of a combustion cycle e.g. is gained through integration. A mean indexed mean pressure PIQ, on the other hand, is the mean value over time of several indicated mean pressures PI, that is to say the indicated mean pressure of several combustion cycles. The diagram of FIG. 1 now shows the normalized, indicated mean pressure PI / PIQ of a combustion cycle with each cross shown.

Overall, a whole number of these indicated mean pressures are plotted in this diagram. If a single combustion cycle, i.e. a single cross in the diagram, has a value with respect to its normalized indicated mean pressure PI / PIQ that is greater than 1.0, then this combustion cycle is one that normally does not have any negative consequences for the engine runs smoothly. With combustion cycles, on the other hand, whose standardized indexed mean pressure PI / PIQ has a value less than 1.0, disturbances in running smoothness can be expected. Such combustion cycles are also known under the term entrained combustion, which term can also be explained on the basis of the diagram in FIG. 1, since normalized indicated mean pressures PI / PIQ, which are less than 1.0, generally occur later than those with respect to the crankshaft angle whose values are greater than 1.0. The occurrence of these delayed burns can be observed in particular when the operating mixture of the internal combustion engine is emaciated and / or diluted with exhaust gases. In this case, these delayed burns also occur when the engine's running limit is approached in this way even if the ignition timing is optimally set. The consequence of such a delayed course of combustion is a reduced torque contribution of this combustion to the overall operation of the internal combustion engine, which then has a negative effect on the smooth running of the internal combustion engine. For this reason, such prolonged burns should be avoided if possible.

The diagram in FIG. 2 shows the radiation maxima in the combustion chambers of the internal combustion engine. Here again shows the abscissa of the diagram shows the crankshaft angle after top dead center in angular degrees, while the ordinate plots the radiation maximum SM related to an average radiation maximum SMQ. The radiation maximum SM is understood to mean a value that expresses the maximum light intensity of a combustion during a specific combustion cycle. An average radiation maximum SMQ is then the mean value of a plurality of successive radiation maxima, that is to say an average radiation maximum over several combustion cycles. Analogously to FIG. 1, each cross represented in the diagram in FIG. 2 represents a value of a normalized radiation maximum SM / SMQ of a specific combustion cycle.

If one considers the individual combustion cycles in a specific combustion chamber, each combustion cycle can be assigned a value of a standardized indexed mean pressure PI / PIQ and a value of a standardized radiation maximum SM / SMQ. For this reason, each cross of the diagram in FIG. 1 also has a corresponding cross in the diagram in FIG. 2. It has been found for the delayed burns that affect the smoothness of the operation that, with such a delayed combustion process, the radiation emission of the combustion that occurs is lower than the mean radiation emission, i.e. in the case of carried-over combustion, the value for the normalized radiation maximum SM / SMQ is less than 1.0. This reduced light intensity is the result of the reduced temperature and pressure level during combustion cycles which are delayed in this way. Because of the non-linear relationship between the temperature in the combustion chamber, the pressure in the combustion chamber and the resulting pressure The resulting radiation maximum or indexed pressure basically has no linear relationship between the normalized indicated mean pressure in FIG. 1 and the normalized radiation maximum in FIG. 2. In the case of the postponed burns, on the other hand, measurements and experiments, in particular, have shown that there is a delay in such burns there is a quadratic relationship between the standardized indexed mean pressure PI / PIQ and the standardized radiation maximum SM / SMQ, namely (1-SM / SMQ) ^{2 =} 1-PI / PIQ.

FIG. 3 shows the relationship just mentioned between the indicated mean pressure and the radiation maximum in a combustion chamber of an internal combustion engine. It can be seen from the diagram that the relationship between the indicated mean pressure and the radiation maximum, namely (1-SM / SMQ) ² - 1 - PI / PIQ, corresponds very well with the measurements carried out.

With regard to FIGS. 1 to 3 described so far, two different methods for controlling the combustion in the combustion chambers of a brewery engine are basically possible. On the one hand, it is possible to detect the carried-over combustions with the aid of the measurement of the pressure curve in a combustion chamber of the internal combustion engine, in order then to influence the subsequent burns in the corresponding combustion chamber of the internal combustion engine in such a way that the carried-over combustions depend on these delayed combustion cycles if possible no longer occur. On the other hand, it is also possible, instead of the pressure curve, to carry out a control corresponding to the first possibility using the curve of the light intensity in the combustion chamber of the internal combustion engine.

Figure 4 shows a possible embodiment of a control. The reference number 10 denotes an internal combustion engine from which an output signal is connected to a maximum value detection 11. In connection with the present regulation, the output signal is the course of the light intensity in a combustion chamber of the internal combustion engine. At the output of the maximum value detection 11, there is therefore the signal SM, which has already been explained in more detail, that is to say the value of the radiation maximum during a combustion cycle of the cylinder in question. This output signal of the maximum value detection 11 is now supplied on the one hand with an averaging 12 and a link 13. The mean value formation 12 forms the signal SMQ from the signal SM, that is to say the mean radiation maximum over several combustion cycles. This signal SMQ is fed to the link 13 as a second input signal. The link 13 forms the difference from the two signals SM and SMQ and forwards this output signal, which is designated ASMN, to a conversion 14. The shaping 14 has the task of recognizing and hiding the carried-over burns. This is achieved in that the signal ASMN only passes on the positive values at the output of the shaping 14 as the output signal ASM. This output signal ASM is then applied to a squaring 15, so that the classification 16 following the squaring 15 is supplied with the signal ASM ² . The output signal of classification 16 is marked with UK. Regulation 17 is then applied to this signal UK. Finally, a pilot control is identified by the reference number 18, this pilot control 1a of general operating parameters and / or operating parameters of the internal combustion engine and / or other sig can be controlled. The output signal of the control 17 and the output signal of the pilot control 18 are linked to one another with the aid of a link 19, the output signal of this link 19 then influencing the internal combustion engine 10 mentioned at the beginning.

Overall, the exemplary embodiment in FIG. 4 shows a device for regulating the burns in the combustion chambers of an internal combustion engine, in which the value of the radiation maximum SM is generated with the aid of the maximum value detection 11 and in which the value of the mean radiation maximum SMQ is formed therefrom with the aid of the averaging 12 in which the signal ASMN = SMQ - SM controls the conversion 14 with the aid of the link 13, so that this conversion 14 can filter out the delayed combustion cycles by suppressing the negative values of the signal ASMN, in which the squaring 15 a transition is made from the radiation maxima to the indicated mean pressures, in order to finally influence the internal combustion engine via the classification 16 and the controller 17.

The classification or classification 16 serves the purpose of dividing the values of the signal ASM ² according to their size into a certain number of classes and of generating a value UK belonging to the respective class. An exemplary embodiment of a possible classification is shown in the diagram in FIG. There, the signal ASM ² between the values 0 and 1 is plotted on the abscissa of the diagram, while the ordinate of the diagram represents the signal UK. It is important in the classification shown that a negative value of the UK signal is generated in the smallest class of the ASM ² signal.

As an example, let the signal ASMN be relatively small, that is to say the deviation of the signal SM from the signal SMQ is relatively small, which is synonymous with a small number of entrained burns. Since a small value ASMN also results in only a small value ASM 2, it is now further assumed that this small value ASM 2 falls in the smallest class of the diagram in FIG. 5, that is to say has a negative value for the signal UK.

However, this negative signal UK then has the consequence that the pilot control value of the pilot control 18 is further reduced in the direction of a smaller fuel quantity on the basis of the output signal of the control 17, that is to say the fuel / air mixture is further leaned relative to the pilot control value, that is to say is approached even closer to the running limit of the internal combustion engine. This can now have the consequence that the closer the internal combustion engine is to the running limit, the more carried-over burns occur. As a result, the value of the signal ASMN increases, so that at some point the value of the signal ASM ² no longer falls into the lowest class of the diagram in FIG. 5 and the value of the signal UK thus becomes positive. However, this then has the consequence that the fuel / air mixture of the internal combustion engine is enriched again more due to the output signal of the control 17, that is to say more fuel is supplied to the internal combustion engine, so that the internal combustion engine again moves somewhat away from its running limit. With the relationship shown in FIG. 5 between the signal ASM ² and the signal UK, it is therefore possible to lean the mixture supplied to the internal combustion engine below the pilot control value.

If, on the other hand, one considers the case, which is shown in broken lines in the diagram in FIG. 5, that the signal UK cannot become negative, the mixture supplied to the internal combustion engine can only be emaciated as much as is thinned out by the control shown in the figure pre-control value supplied by the pre-control 18 is defined. In this case, the regulation of FIG. 4 could be regarded rather as a monitoring which only enriches the mixture in the case of carried-over burns in order to suppress these carried-away burns again.

The advantage of the classification shown in FIG. 5 lies in the fact that it can be used to specifically weight the deviation from a desired smoothness. E.g. If there are only small numbers of burns that have been carried over, this also results in only minor reactions. On the other hand, with large numbers of carried-over burns, the regulation described also reacts correspondingly strongly in accordance with the classification. Smaller fluctuations of these numbers of delayed burns, however, as well as short-term "peaks" of these numbers, however, do not immediately result in correspondingly strong reactions due to the classifications, but only longer lasting, major changes in these numbers also cause a change in the output signal of the classification.

Due to the fact that only the carried-over combustions are used to regulate the internal combustion engine, it is possible to build up an extremely fast regulation. With the help of the classification, however, there is also the possibility of the entire Stabilize regulation. As a result, an influence on the internal combustion engine is specified with the aid of the device shown in FIG. 4, with the aid of which the internal combustion engine can be operated as close as possible to its running limit, but at the same time has the greatest possible smoothness.

The pilot control 19 can be a control as well as a regulation. These can then be dependent, e.g. the speed of the internal combustion engine, the load applied to the internal combustion engine, the temperature of the internal combustion engine, the air flow rate in the intake pipe of the internal combustion engine, etc.

It is also possible to take the classification 16 into account in the squaring 15 in the control shown in FIG. 4 or, if this is possible from a control-technical point of view, to omit the classification 16 entirely.

In the previously described method for controlling the combustion in the combustion chambers of an internal combustion engine, the amount of fuel supplied to the internal combustion engine was influenced, for example. However, it is also possible instead to change the exhaust gas recirculation quantity supplied to the internal combustion engine with the aid of a corresponding actuator. It is also possible to influence the output signals generated by the pilot control 18 as a function of the exhaust gas composition, so that an exact monitoring of the running limit can then be carried out in the event of a thinning of the mixture supplied to the internal combustion engine. In this case, however, the value of the UK signal must not assume negative values. One more way influencing the internal combustion engine consists in changing or regulating the ignition timing of the internal combustion engine, but in this case only regulating the ignition timing towards a later ignition is permitted.

As has already been explained, it is only important to recognize the carried-over combustion in a combustion chamber of an internal combustion engine. There are several options for how this is recognized. It has already been mentioned that this detection can be carried out with the aid of the indicated mean pressures, as well as by means of the radiation maxima. Furthermore, however, it is also possible to detect the carried-over combustions by integrating them via the radiation emission of a combustion cycle or to draw conclusions about the aforementioned delayed combustions from the maximum of the ion current in the combustion chamber of the internal combustion engine.

The timing of the occurrence of a delayed combustion, i.e. the exact crankshaft angle, is not absolutely decisive for the present regulation. However, it is possible to also use the crankshaft angle signal to identify the carried-over combustion. A signal relating to the combustion position of the combustion in a combustion chamber of the internal combustion engine can then be used instead of a crankshaft angle signal, this signal relating to the combustion position, for example, from the pressure curve in the combustion chamber of the internal combustion engine or from the position of the pressure maximum or from the curve of the light intensity in the combustion chamber the internal combustion engine or from the light maximum or can be obtained from the moment a flame front arrives at an ion current probe.

Finally, it is also possible to classify 16 e.g. with the help of a second squaring with negative zero point or with the help of a proportional element with dead zone and negative output within the dead zone.

Another way of designing the invention is e.g. to use the object of Figure 4 for measuring the uneven running of an internal combustion engine. For display, e.g. the signal UK come, that is, the respective content of the classifier 16 and thus a measure of the smooth running or rough running of the internal combustion engine.

With all these possibilities of changing the regulation indicated in FIG. 4, elements that have not been changed may then have to be adapted to the corresponding change. It is also possible to implement all of the changes described individually or in combination.

Claims (12)

1. A method for controlling the burns in the combustion chambers of an internal combustion engine, characterized in that in a first step entrained combustion, i.e. Combustions that occur too late in the combustion chambers of the internal combustion engine are recognized and that in a second step, depending on the carried-over combustion, the carry-over of which exceeds a certain, predeterminable value, the burns in the combustion chambers of the internal-combustion engine are influenced with a view to reducing the carry-over. 2. The method according to claim 1, characterized in that the carried over burns are detected with the aid of the pressure curve in the combustion chambers of the internal combustion engine. 3. The method according to claim 2, characterized in that the carried over burns are detected with the aid of the indicated medium pressure. 4. The method according to claim 1, characterized in that the carried over burns are detected with the aid of the course of the light intensity in the combustion chambers of the internal combustion engine. 5. The method according to claim 4, characterized in that the carried over burns are detected with the aid of the maximum of the light intensity in the combustion chambers of the internal combustion engine. 6. The method according to claim 1, characterized in that the entrained burns are detected by means of the forward movement of the flame front in the combustion chambers of the internal combustion engine. 7. The method according to claim 6, characterized in that the entrained burns are detected with the help of the arrival of the flame front at a certain point in the combustion chamber. 8. The method according to claim 1, characterized in that the burns in the combustion chambers of the internal combustion engine by means of the fuel metering and / or the exhaust gas recirculation _- and / or the ignition angle setting and / or the fresh air supply are influenced. 9. The method according to at least one of claims 1 to 8, characterized in that the input signal of the actual control with the help of a classification or classification can only take certain, predetermined values. 10. A device for carrying out the method for controlling the burns in the combustion chambers of an internal combustion engine, characterized in that the radiation maximum is detected during a combustion cycle in a combustion chamber of an internal combustion engine with the aid of a maximum value detection, that it is recognized with the aid of at least one averaging whether it is in the combustion cycle is a delayed combustion, that with the help of a potentiation, preferably a squaring, from the radiation maximum to the indicated mean pressure of the combustion, that with the help of a classification the signal driving the subsequent regulation assumes certain, predeterminable values, and that with the aid of the output signal the control affects the internal combustion engine. 11. The device according to claim 10, characterized in that the internal combustion engine is further influenced by a pilot control, which in turn is dependent on at least one operating parameter of the internal combustion engine. 12. The device according to claim 10, characterized in that the entire device is used for measuring the uneven running of the internal combustion engine.

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