DE102020200222B4 - Method for controlling an internal combustion engine and internal combustion engine - Google Patents

Abstract

Method for controlling a multi-cylinder internal combustion engine (1), the internal combustion engine (1) having at least two cylinders (3; 5; 7), exhaust gas temperatures of the at least two cylinders (3; 5; 7) being recorded in a first step (S1). , wherein in a second step (S2) a temperature reference value is determined from the detected exhaust gas temperatures, wherein in a third step (S3) a first exhaust gas temperature of a first cylinder (3) of the at least two cylinders (3; 5; 7) is compared with the temperature reference value in a fourth step (S4) a correction signal is transmitted to a cylinder controller of the first cylinder (8), a knock signal assigned to the first cylinder (3) being used to determine the correction signal when a temperature comparison value exceeds or falls below a threshold value, an ignition timing of the first cylinder (3) being advanced by means of the cylinder control when the knock signal is within an acceptable range of values, or is retarded when the knock signal is within an unacceptable range of values.

Description

The invention relates to a method for controlling an internal combustion engine and an internal combustion engine that is set up to carry out such a method.

Methods and internal combustion engines of the type discussed here are known. In these known methods and internal combustion engines, the combustion in the respective cylinders typically takes place with a time delay. Due to component tolerances, gas-dynamic effects, differences in the ignition conditions and differences in the opening and closing times of the intake and exhaust valves and the dynamics of the internal combustion engine, the various cylinders are operated at different levels of performance and thus to different degrees, especially with regard to pressure, burdened. Such an uneven load on the various cylinders leads to a reduction in the efficiency of the internal combustion engine as a whole, since the respective cylinders are not all operated at their respective optimum power point. In addition, the power transmission from the cylinders to a crankshaft is uneven over time due to the ignition being offset in time, which also reduces the overall efficiency of the internal combustion engine. In addition, the different levels of pressure exerted on the cylinders cause above-average wear on individual cylinders, making maintenance expensive and increasing the risk of malfunctions in the internal combustion engine.

Since the performance level of the cylinders is directly related to the pressure load, i.e. to the pressures occurring in the cylinders, the known methods and internal combustion engines attempt to equalize the cylinders in terms of their performance by means of cylinder pressure-controlled systems. However, these cylinder pressure-controlled systems are complex and expensive to develop. The service lives of such internal combustion engines are also short.

From the DD 249 941 A1 It is also known that a cylinder load distribution and thus the performance of the cylinders can be equalized depending on the exhaust gas temperatures of the cylinders by determining a mean value from the individual exhaust gas temperatures of all cylinders and determining the deviation of the individual exhaust gas temperatures from the mean value. This deviation is then used to adjust an injection quantity of a fuel.

Furthermore, from the EP 2 310 654 B1 known that in diesel engines to set a desired exhaust gas temperature and to adjust the forces generated by the cylinders, an injection period can be adjusted, in which in EP 2 310 655 B1 it is further stated that the injection duration is selected on the basis of a measurement of the torsional vibration of a crankshaft of the internal combustion engine.

In DE 10 2004 060 893 A1 is described for an Otto gas engine, which general effects a change in ignition timing has on the exhaust gas temperature of the Otto gas engine, with the ignition timing being shifted forward in particular to lower the exhaust gas temperature and a later ignition timing being selected to increase the exhaust gas temperature.

The object of the invention is to create a method for controlling an internal combustion engine and an internal combustion engine set up for carrying out the method, the disadvantages mentioned being avoided.

The object is solved by creating the subject matter of the independent claims. Advantageous configurations result from the dependent claims.

The object is achieved in particular by creating a method for controlling a multi-cylinder internal combustion engine, the internal combustion engine having at least two cylinders, exhaust gas temperatures of the at least two cylinders being detected in a first step, with a temperature reference value being calculated from the detected exhaust gas temperatures in a second step, in particular an average temperature value, is determined, with a first exhaust gas temperature of a first cylinder of the at least two cylinders being compared with the temperature reference value in a third step, and with a correction signal being sent to a cylinder controller of the first cylinder in a fourth step - in particular as a function of the comparison Cylinder is transmitted. As a result, irregularities in the ignition of the at least two cylinders can be detected and, if necessary, an appropriate measure can be initiated by means of the correction signal in order to set a desired, in particular uniform, load distribution of the cylinders. In addition, this method can be implemented cost-effectively, since the exhaust gas sensor devices required to carry out the method and their installation are already known and no additional development work is required. In particular, the exhaust gas temperatures can be detected using sensors that are already installed in a finished internal combustion engine. In such finished internal combustion engines, especially in gas engines, so no corresponding conversion measures are required and in the production of new internal combustion engines in which a Recording the exhaust gas temperature is already provided for other reasons, can be dispensed with additional sensors. It is provided that when a temperature comparison value exceeds or falls below a threshold value, a knock signal assigned to the first cylinder is used to determine the correction signal. This prevents the correction carried out as part of this method from causing a knock limit to be exceeded. Provision is also made for the cylinder controller to advance an ignition point of the first cylinder if the knock signal is in an acceptable range of values, or to retard it if the knock signal is in an unacceptable range of values. Thus, the ignition timing is allowed to advance if the knock signal is acceptable. This avoids damage and wear on the internal combustion engine. Furthermore, the efficiency of the internal combustion engine can be increased by advancing the ignition point.

Knocking combustion typically occurs when the first exhaust gas temperature is below the temperature reference value. In this case, the knock signal is in the unacceptable value range and an advance of the ignition timing should be avoided. In particular, checking the knock signal also prevents the ignition timing from being advanced if the threshold value was exceeded by the temperature comparison value and the knock signal is nevertheless in the unacceptable value range. This avoids wear and tear in any case.

The knock signal required for this is preferably detected. Alternatively, the knock signal has already been detected using a separate method and is provided for the present method.

The accepted range of values is in particular a range in which no knocking combustion occurs. The unacceptable range of values, on the other hand, is in particular a range in which knocking combustion occurs.

An exhaust gas temperature is understood here to mean a temperature of an exhaust gas that is expelled, in particular burned, from a combustion chamber of the cylinder. This temperature of the exhaust gas can still change after it has left the combustion chamber, in particular due to cooling of the exhaust gas. It is important that the temperature of the exhaust gas is recorded and a combustion chamber temperature or an exhaust gas temperature at a fixed location in the exhaust line can be inferred from this, and/or that all exhaust gas temperatures of all of the at least two cylinders are at a fixed location, in particular with regard to the respective cylinder same position, so that all exhaust gas temperatures can be compared with one another under the same comparison conditions.

A temperature reference value is understood here to mean, in particular, an arithmetic mean, a median or another statistical parameter which at least partially describes the temperature distribution of the at least two cylinders. In order to determine the temperature reference value, the exhaust gas temperatures used for the determination are preferably weighted, individual exhaust gas temperatures in particular being multiplied by a weighting factor.

A correction signal is understood here to mean, in particular, a signal which causes an ignition timing adjustment, a change in an injection quantity and/or a change in a combustible gas composition to be injected. This brings about a change in an individual cylinder output, with the individual cylinder output preferably being changed in the direction of an average cylinder output of the at least two cylinders.

The exhaust gas temperatures are preferably each associated with an individual cylinder of the at least two cylinders such that the first exhaust gas temperature is the temperature of the exhaust gas exhausted from the first cylinder and a second exhaust gas temperature is the temperature of the exhaust gas exhausted from a second cylinder of the at least two cylinders. Thus, in the first step in detecting the exhaust gas temperatures, an exhaust gas temperature distribution of the at least two cylinders is detected.

In particular, it is possible for the internal combustion engine to have, in addition to the at least two cylinders, other cylinders whose exhaust gas temperatures are not recorded. It is therefore not necessary for all cylinders of the internal combustion engine to be used when carrying out the method. Rather, the method can also only be carried out for some of all cylinders, namely the at least two cylinders. However, the method is preferably carried out for all cylinders of the internal combustion engine.

When comparing the first exhaust gas temperature with the temperature reference value, it is preferably determined whether the exhaust gas temperature deviates from the temperature reference value. The size of the deviation is particularly preferably determined.

Preferably, in particular in the third step, the second exhaust gas temperature of the second cylinder and/or all exhaust gas temperatures are also measured of all cylinders of the at least two cylinders is compared with the temperature reference value. Furthermore, further correction signals are preferably transmitted to a cylinder controller of the second cylinder and/or the at least two cylinders, particularly in the fourth step—in particular as a function of the respective comparison. As a result, the method can be used to control a plurality of cylinders, in particular at the same time, as a result of which equalization in terms of performance can be achieved more quickly and the efficiency of the internal combustion engine is therefore particularly high.

According to one development of the invention, it is provided that when comparing the first exhaust gas temperature with the temperature reference value, the temperature comparison value, in particular a temperature difference between the first exhaust gas temperature and the temperature reference value, is determined and/or it is checked whether the temperature comparison value exceeds the threshold value. As a result, the deviation of the first exhaust gas temperature from the temperature reference value is determined precisely and in particular quantitatively, so that a particularly precise correction is possible and iterations during the correction are avoided.

A threshold value is understood here as meaning a particularly positive temperature threshold value which is predetermined or—in particular during the method—is determined using the temperature reference value and/or the exhaust gas temperature and/or other operating parameters of the internal combustion engine. The threshold value defines an upper limit of a temperature range starting from the temperature reference value. As a result, the threshold value indicates a maximum permissible temperature above the temperature reference value and thereby defines a permissible range for the first, in particular for all, exhaust gas temperatures.

The temperature difference is preferably formed in such a way that it is greater than zero, i.e. positive, when the first exhaust gas temperature is greater than the temperature reference value, with the temperature difference being less than zero, i.e. negative, when the exhaust gas temperature is less than the temperature reference value.

Corresponding temperature comparison values for the second exhaust gas temperature and/or all of the at least two exhaust gas temperatures are preferably determined, it being particularly preferably checked in each case whether the threshold value is exceeded and/or how large the deviation from the threshold value is.

According to a development of the invention, it is provided that the threshold value is 5 Kelvin. This value is a good indicator of an efficiency-reducing combustion process in the internal combustion engine, so that inefficiency is reliably detected when the temperature comparison value exceeds the threshold value. On the other hand, this value avoids excessive regulation of the internal combustion engine, since temperature comparison values that are less than 5 Kelvin do not result in a correction signal. As a result, the at least two cylinders are loaded very evenly and combustion processes that reduce efficiency are avoided.

According to a further development of the invention, it is provided that the temperature comparison value exceeds a threshold value, ie a quantitative measure for exceeding the threshold value, which is used to determine the correction signal. This enables precise correction of the combustion. In particular, overshoots are avoided during the correction, as a result of which the cylinder could be brought into an operating range that is inefficient in relation to the optimal operating point. In particular, this also prevents knocking of the internal combustion engine.

In this case, the correction signal is preferably adjusted proportionally to the exceeding of the threshold value. Alternatively, the correction signal is adjusted disproportionately to the exceeding of the threshold value, so that the correction, ie countermeasures against rapidly changing cylinder outputs, takes place particularly effectively.

Alternatively or additionally, the correction signal is set as a function of the temperature comparison value, with the correction signal preferably being set proportionally or overproportionally to the temperature comparison value.

According to a development of the invention, it is provided that the correction signal causes an ignition timing adjustment, in particular to advance or retard the ignition timing of the first cylinder. This allows the power of the cylinder to be well controlled so that the internal combustion engine can be operated efficiently and wear is avoided.

The correction signal is thus set in such a way that—after transmission to the cylinder controller—an ignition timing is advanced or retarded. Alternatively, the correction signal is set in such a way that an ignition timing adjustment is not carried out, in particular is prevented.

Preferably, when the first exhaust gas temperature is greater than the temperature reference value, the ignition timing is advanced all the way especially if the temperature comparison value exceeds the threshold value. As a result, a cylinder subject to an above-average thermal load is brought closer to the other cylinders of the at least two cylinders in terms of its performance level. Overall, this leads to an increase in efficiency and reduced wear and tear on the internal combustion engine.

The ignition timing is also preferably retarded when the first exhaust gas temperature is lower than the temperature reference value. In this state - before the ignition timing is retarded - the first cylinder is subjected to a below-average thermal load and an above-average mechanical load, so that the first cylinder is at a relatively high, individual performance level compared to the other cylinders. By lowering the individual output of the first cylinder, the overall efficiency of the internal combustion engine is increased and wear is avoided.

According to one development of the invention, it is provided that when the temperature comparison value falls below the threshold value, at least no advance adjustment of the ignition point of the first cylinder is carried out. This avoids a correction that is disadvantageous with regard to the efficiency of the internal combustion engine being carried out, so that the overall efficiency is high.

Preferably, a blocking signal is transmitted to the cylinder controller as a correction signal, which at least prevents the ignition point from being advanced.

According to one development of the invention, it is provided that the method is carried out above a predetermined power limit of the internal combustion engine and is not carried out below the predetermined power limit. This ensures that the internal combustion engine starts reliably, ie as long as the predetermined performance limit has not yet been reached. In addition, the efficiency of the internal combustion engine is increased and wear is reduced above the power limit, in particular in stationary operation after the starting process, particularly at a rated load or partial load.

The object is also achieved in particular by creating an internal combustion engine with at least two cylinders, the internal combustion engine having at least two temperature sensors and a control unit operatively connected to them, the temperature sensors and the control unit being arranged and set up to measure exhaust gas temperatures of the at least two cylinders, in particular a first exhaust gas temperature of a first cylinder and a second exhaust gas temperature of a second cylinder, the internal combustion engine being set up to carry out a method according to one of the preceding specific embodiments. As a result, wear and tear on the internal combustion engine during operation is avoided and efficiency is increased. In addition, the cost of the internal combustion engine, particularly the development cost and assembly cost of the internal combustion engine, is low.

The internal combustion engine is preferably designed as a reciprocating piston engine.

The descriptions of the method and the internal combustion engine are to be understood as complementary to one another. In particular, features of the internal combustion engine that have been described explicitly or implicitly in connection with the method are preferably features of the internal combustion engine, either individually or in combination with one another. The internal combustion engine is preferably designed to carry out at least one of the method steps described in connection with the method. Method steps that have been described explicitly or implicitly in connection with the internal combustion engine are preferably individually or in combination with one another steps of a preferred embodiment of the method. In particular, at least one step that results from at least one feature of the internal combustion engine is preferably provided as part of the method.

• 1 ein erstes Verfahren gemäß einer ersten Ausführungsform zur Regelung einer mehrzylindrigen Brennkraftmaschine,
• 2 ein zweites Verfahren gemäß einer zweiten Ausführungsform zur Regelung einer mehrzylindrigen Brennkraftmaschine, und
• 3 eine schematische Darstellung der mehrzylindrigen Brennkraftmaschine, welche zur Durchführung des Verfahrens gemäß der ersten und/oder zweiten Ausführungsform eingerichtet ist.

The invention is explained in more detail below with reference to the drawing. It shows:

• 1 a first method according to a first embodiment for controlling a multi-cylinder internal combustion engine,
• 2 a second method according to a second embodiment for controlling a multi-cylinder internal combustion engine, and
• 3 a schematic representation of the multi-cylinder internal combustion engine, which is set up to carry out the method according to the first and/or second embodiment.

1 shows a first method for controlling a multi-cylinder internal combustion engine according to a first embodiment, the internal combustion engine having at least two cylinders, namely a first cylinder and a second cylinder. In a first step S1, exhaust gas temperatures of the at least two cylinders are recorded. At least a first exhaust gas temperature of the first cylinder and a second exhaust gas temperature of the second cylinder are therefore recorded. From the exhaust gas temperatures recorded in this way, in particular the first exhaust gas temperature and the second Exhaust gas temperature, is then - determined a temperature reference value - in a second step S2. In a third step S3, the first exhaust gas temperature is compared with the temperature reference value. In addition, in a fourth step S4, a correction signal is transmitted to a cylinder controller of the first cylinder. This method prevents the internal combustion engine from being operated with low efficiency. In addition, the costs are low compared to known methods, since exhaust gas sensors are typically already installed and can be used for this method.

A temperature comparison value is preferably determined in a fifth step S5, in particular during the comparison in the third step S3 of the first exhaust gas temperature with the temperature reference value.

In the embodiment of the first method shown here, the temperature reference value is an arithmetic mean of the at least two exhaust gas temperatures. In an alternative embodiment not shown here, on the other hand, a median or another statistical parameter of an exhaust gas temperature distribution is determined as the temperature reference value.

The temperature comparison value preferably indicates a deviation between one of the exhaust gas temperatures, in particular the first exhaust gas temperature, and the temperature reference value. This deviation is specified here as the difference between the temperature reference value and the exhaust gas temperature, with the temperature comparison value being positive if the exhaust gas temperature is greater than the temperature reference value.

After the comparison in the third step S3 of the first exhaust gas temperature with the temperature reference value, i.e. in particular after the determination of the temperature comparison value in the fifth step S5, in the embodiment shown here it is checked in a sixth step S6 whether the temperature comparison value exceeds a threshold value, which preferably 5 Kelvin is set exceeds.

The correction signal, which is transmitted to the cylinder controller in the fourth step S4, brings about an ignition timing adjustment of an ignition timing of the first cylinder. Depending on the result of the check in the sixth step S6, the ignition point of the first cylinder is advanced or retarded. If the temperature comparison value is greater than the threshold value, the correction signal is selected such that—after transmission of the correction signal to the cylinder controller in the fourth step S4—the ignition timing is advanced in a seventh step S7.

If, on the other hand, the speed comparison value is less than the threshold value, the ignition point is at least not advanced. In this case, an ignition timing adjustment is preferably prevented in an eighth step S8 and is therefore not carried out. The correction signal is selected in such a way that the cylinder control does not cause any adjustment. Alternatively, the ignition point is retarded by means of the correction signal in a ninth step S9. The retardation is carried out in particular when the temperature comparison value is negative.

A further, negative threshold value is particularly preferably determined, which defines a maximum, negative deviation of the first exhaust gas temperature from the temperature comparison value. If the temperature comparison value is negative and also deviates from the temperature reference value by more than the negative threshold value, the retardation is preferably carried out. As a result, cylinders with a comparatively low exhaust gas temperature can be turned up so that they approach an average performance level of the at least two cylinders. This further increases the overall efficiency of the at least two cylinders. In addition, the regulation towards optimal efficiency can be carried out more quickly, since cylinder performance can not only be regulated down but also regulated up.

2 Figure 12 shows a second method according to a second embodiment of the invention. Like the first method according to the first embodiment, this second method includes the first step S1, the second step S2, the third step S3, the fourth step S4, the fifth step S5 and the sixth step S6. In contrast to the first method, in the second method a knock signal test is additionally carried out in a tenth step S10. The correction signal is then determined as a function of the knock signal and the check in the sixth step S6.

The knock signal test in the tenth step S10 can be carried out before or after the test for exceeding the target value in the sixth step S6. In 2 the knock signal check takes place after checking the temperature comparison value of the sixth step S6. If the check establishes that the temperature comparison value is above the threshold value, the state of the first cylinder relative to the other cylinders is defined as a high power state Z1. If, on the other hand, it is determined that the temperature comparison value is not above the threshold value, the state of the first cylinder is set as a low power state Z2.

If the knock signal test reveals that the internal combustion engine is knocking and/or is too strong, the correction signal is selected according to the second embodiment of the method such that the ignition timing is retarded in the ninth step S9. However, if the knock signal check shows that there is no knocking or only negligible knocking, the ignition point is advanced or not adjusted depending on the checking in the sixth step S6. The ignition timing is advanced according to the seventh step S7 if the temperature comparison value exceeds the threshold value, with no ignition timing adjustment being carried out if the temperature comparison value does not exceed the threshold value.

3 shows an internal combustion engine 1 with at least two cylinders, namely a first cylinder 3 and a second cylinder 5. It is possible for the internal combustion engine 1 to have additional cylinders 7 in addition to the first cylinder 3 and the second cylinder 5, which are only indicated in the drawing and are not explicitly shown. Each of the cylinders 3 , 5 , 7 can be supplied with a fuel via a fuel feed line 9 .

In addition, internal combustion engine 1 has at least two temperature sensors, namely a first temperature sensor 11 and a second temperature sensor 13. Each of these temperature sensors is assigned to a cylinder 3, 5, 7. In the exemplary embodiment illustrated here, the temperature sensors 11 , 13 are each arranged on an exhaust line 15 of the internal combustion engine 1 . By means of a control unit 17 operatively connected to the temperature sensors, they are also set up to—according to one of the previously described embodiments of the method—detect exhaust gas temperatures and/or advance and/or retard the ignition times of the first cylinder 3 and/or the second cylinder 5 adjust.

The control unit 17 is also set up to control the cylinders 3, 5, 7 depending on the detected exhaust gas temperatures. For this purpose, the correction signal is determined according to one of the methods described above and transmitted to a cylinder control unit of the control device. In order to record the exhaust gas temperatures and to control the first cylinder 3 and/or the second cylinder, the internal combustion engine 1 has control lines 19, which the control unit 17 connects to the first cylinder 3 and/or the second cylinder 5 and the first temperature sensor 11 and/or the second temperature sensor 13.

Thus, all cylinders 3, 5, 7 of the internal combustion engine 1 can be matched to one another in terms of performance, as a result of which the efficiency of the internal combustion engine 1 is very high. In addition, as a result, the wear on the cylinders 3, 5, 7 and the costs are very low.

Claims (8)

Method for controlling a multi-cylinder internal combustion engine (1), the internal combustion engine (1) having at least two cylinders (3; 5; 7), exhaust gas temperatures of the at least two cylinders (3; 5; 7) being recorded in a first step (S1). , wherein in a second step (S2) a temperature reference value is determined from the detected exhaust gas temperatures, wherein in a third step (S3) a first exhaust gas temperature of a first cylinder (3) of the at least two cylinders (3; 5; 7) is compared with the temperature reference value in a fourth step (S4) a correction signal is transmitted to a cylinder controller of the first cylinder (8), wherein if a temperature comparison value exceeds or falls below a threshold value, a knock signal assigned to the first cylinder (3) is used to determine the correction signal, an ignition timing of the first cylinder (3) being advanced by means of the cylinder control when the knock signal is within an acceptable range of values, or is retarded when the knock signal is within an unacceptable range of values. procedure after claim 1 , characterized in that when comparing the first exhaust gas temperature with the temperature reference value, the temperature comparison value is determined and/or it is checked whether the temperature comparison value exceeds the threshold value. Method according to one of the preceding claims, characterized in that the threshold value is 5 Kelvin. Method according to one of the preceding claims, characterized in that a threshold value exceeding of the temperature comparison value is determined, which is used to determine the correction signal. Method according to one of the preceding claims, characterized in that the correction signal causes an ignition timing adjustment of the ignition timing of the first cylinder (3). Method according to one of the preceding claims, characterized in that at If the temperature comparison value falls below the threshold value, at least no advance adjustment of the ignition point of the first cylinder (3) is carried out. Method according to one of the preceding claims, characterized in that the method is carried out above a predetermined power limit of the internal combustion engine (1) and is not carried out below the predetermined power limit. Internal combustion engine (1) with at least two cylinders (3; 5; 7), the internal combustion engine (1) having at least two temperature sensors (11; 13) and a control unit (17) operatively connected to them, the temperature sensors (1 1; 13) and the control unit (17) is arranged and set up to detect exhaust gas temperatures of the at least two cylinders (3; 5; 7), the internal combustion engine (1) being set up to carry out a method according to one of the preceding claims.

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