EP0191167B1 - Method and apparatus for the regulation of the combustions in the combustion chambers of a combustion engine - Google Patents

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. A control circuit can then be established by specifying the target crankshaft angle and comparing it with the light signal-dependent actual crankshaft angles to control, 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.

Furthermore, from DE-A-32 10 810 a method for influencing the charge composition in a spark-ignited internal combustion engine is known, in which crankshaft angles are detected when the maximum light intensity is determined in the combustion chamber and a scatter control is based on this. According to FIG. 2, it is therefore a question of regulating the scatter of angular values at which certain events occur in the combustion chamber to a specific value.

It has now been shown that even with this solution, optimal combustion chamber control is not yet possible.

Advantages of the invention

The method according to the invention for controlling an internal combustion engine with the features of the main claim has the advantage over the prior art described that only the 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 of particular advantage not to control the actual control with a linear signal, but to divide this linear signal into individual classes in order to then carry out the control 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 indexed mean pressure PI is understood to mean an average pressure level in a combustion chamber of the internal combustion engine, which is obtained during the period of a combustion cycle, for example by means of 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 when 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 as far as 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 normalized indicated mean pressure PI / PIQ and the normalized 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, basically two different methods for controlling the combustion in the combustion chambers of an internal combustion engine are possible. On the one hand, it is possible to identify 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 as a function of these delayed combustion cycles in such a way that the carried-over combustions do not possibly occur occur more. 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 relevant cylinder. 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 deformation 14 has the task of recognizing and hiding the carried-over burns. This is achieved in that only the positive values at the output of the conversion 14 are passed on as the output signal ASM by the signal ASMN. 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. This signal UK is then applied to control 17. Finally, a pilot control is identified by reference number 18, this pilot control 18 of general operating parameters and / or operating parameters of the internal combustion engine and / or other signals 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 average radiation maximum SMQ is formed therefrom with the aid of the averaging 12 , in which the signal ASMN = SMQ - SM controls the transformation 14 with the aid of the link 13, so that this transformation 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 into a certain number of classes according to their size 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 ASM² 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 ASM² 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 ASM², it is now further assumed that this small value ASM² 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 result that the pilot control value of the pilot control 18 is reduced further 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 still is approached 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. This increases the value of the signal ASMN, so that at some point the value of the signal ASM² 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.

On the other hand, if 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 can be thinned out by means of the control shown in FIG the pilot control value supplied by the pilot 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 long-term, 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. However, it is also possible to continue; to detect the entrained burns by integrating them via the radiation emission of a combustion cycle or to infer the aforementioned delayed burns via the maximum of the ion current in the combustion chamber of the internal combustion engine.

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 (7)

1. Method for the closed-loop control or open-loop control of the combustions in the combustion chambers of an internal combustion engine via operating variables such as fuel metering, exhaust-gas recirculation, ignition-angle setting and fresh-air supply, based on the amplitudes of the characteristic variables light intensity or pressure in the combustion chamber being recorded as actual values, characterised in that an average formation (12) of at least two amplitudes of one of the characteristic variables is performed for the purpose of setpoint formation and the differences between setpoint and actual values are determined and those differences which indicate delayed combustions are detected with the aid of a sign detection (14) and only these differences are used as input values of an open-loop or closed-loop countercontrol.
2. Method according to Claim 1, characterised in that the differences between setpoint and actual values are classified according to their magnitude and the open-loop or closed-loop counter control proceeds in accordance with a classification (16) in discrete steps.
3. Method according to at least one of Claims 1 and 2, characterised in that, with the aid of an involution, preferably a squaring, the light maxima are used to infer the indicated mean effective pressures as the average pressure levels in the combustion chambers of the internal combustion engine during the combustion cycles.
4. Method according to at least one of Claims 1, 2 and 3, characterised in that the internal combustion engine is furthermore influenced by a precontrol which, for its part, is dependent on at least one operating variable of the internal combustion engine.
5. Method according to at least one of Claims 1, 2, 3 and 4, characterised by additional use for measuring the roughness of running of the internal combustion engine.
6. Device for the closed-loop control or open-loop control of the combustions in the combustion chambers of an internal combustion engine via operating variables such as fuel metering, exhaust-gas recirculation, ignition-angle setting and fresh-air supply, based on the amplitudes of the characteristic variables light intensity or pressure in the combustion chamber being recorded as actual values, characterised in that the average of at least two amplitudes of one of the characteristic variables is determined for the purpose of setpoint formation, in means for average formation (12), the differences between setpoint and actual values are determined in means for difference formation, those differences which indicate delayed combustions are determined in means for sign detection (14) and only these differences serve as input values of the means for open-loop or closed-loop counter control.
7. Device according to Claim 6, characterised in that means for the additional measurement of the roughness of running of the internal combustion engine are provided.

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