JP2012036892A - Control method and device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To equalize contribution to torque, of a plurality of intake injection valves of a plurality of engine cylinders having the intake injection valves and at least one direct injection valve.SOLUTION: Fuel is injected in the cylinder 10 through at least one of the intake injection valves 150 so that resulting fuel/air mixture is lean, then the fuel is injected through at least one of the direct injection valve 110 so that, by the injection through the direct injection valve, contribution to torque of the internal combustion engine is not performed at all and resulting fuel/air mixture is theoretical-fuel/air mixture.

Description

  The present invention relates to an internal combustion engine control method and apparatus.

  From German Offenlegungsschrift 10 2008002511, for example, an internal combustion engine is known in which the injection valve is arranged not only in the intake pipe but also in the combustion chamber. In particular, the combustion method by jets requires a high metering accuracy of the injection valve in order to make optimal use of all the advantages (for example especially for starting up or for warming up or for catalyst (Multiple injection with very small individual injections for heating). The required dispensing accuracy should be ensured by special methods, especially within the minimum amount.

  In internal combustion engines that allow stratified combustion engine operation (geschichteten Motorbetrieb), often the so-called cylinder equalization function is used to equalize the torque ratio of the individual cylinders to the total torque based on the determined rotational irregularity term. The In stratified charge combustion operation, torque is proportional to the injected fuel mass, and this method compensates for the injection valve tolerance with high accuracy.

  In the homogeneous combustion operation (Homogenbetrieb), it is preferable to use the individual cylinder λ control in order to equalize the air-fuel ratio (Luft− / Kraftstoffverhaltnis) for each cylinder. However, this method has narrow limits. Especially when the number of cylinders is large and when a turbocharger is used, the availability of individual cylinder λ control is very limited. For example, the asymmetric firing sequence typically in an eight cylinder engine also presents special difficulties for this method.

DE 198 28 279 already discloses a torque share equalization method for each cylinder of a multi-cylinder internal combustion engine. In this equalization method, for example, a crankshaft is used for cylinder equalization. Alternatively, rotational irregularity signals that appear within various segment times of the camshaft are used. Based on the rotation irregularity signal, the torque share of the individual cylinders is equalized by controlling the injection amount. The cylinder equalization function operates only in stratified charge combustion operation. In contrast, in homogeneous combustion operation or homogeneous lean combustion operation (Homogen-Magerbetrieb), the injection time correction coefficient determined from the pre-control characteristic curve group (Vorsteuerkennfeldern) is used in stratified combustion operation, but cylinder equalization is used. The function is switched off.
From DE 102007020964 it is known how individual cylinders are equalized with respect to their torque shares in order to achieve as good a rotation regularity as possible in an internal combustion engine with direct injection. . Here, the fuel is injected into the combustion chamber of the cylinder by one injection that determines the share of the torque of the internal combustion engine, and the fuel is injected so that the torque becomes neutral in the post-injection during the working stroke of the cylinder. If so, the amount of post-injection is determined so that the exhaust gas corresponds approximately to the theoretical air / fuel mixture.

German Patent Application Publication No. 102008002511 German Patent Application Publication No. 19828279 German Patent Application No. 102007020964

  The object of the present invention is to improve the rotation regularity and reduce emissions, particularly in all cylinders, in an internal combustion engine in which the injection valves are arranged not only in the combustion chamber but also in the intake pipe. The fuel amount of the intake pipe injection valve is calibrated so that all cylinders are equalized so that the fuel amount is injected.

  This problem is solved by the method according to independent claim 1.

  In the method according to the invention, fuel is injected via an intake pipe injection valve so that the synthetic fuel / air mixture is lean. Through at least one direct injection valve, fuel is injected in such a way that no contribution to the torque of the internal combustion engine is made. However, the amount of fuel injected through the direct injection valve is metered so that the synthetic fuel / air mixture is a theoretical fuel / air mixture. This method has the advantage that the torque generated by the internal combustion engine is directly a function of the amount of fuel injected via the intake pipe injection valve. Thereby, the rotational regularity of the internal combustion engine is also directly a function of the injection quantity of the intake pipe injection valve. Therefore, the injection amount of the intake pipe injection valve can be calibrated by the cylinder equalization control based on the rotation regularity in the method according to the present invention. At the same time, the theoretical fuel / air mixture achieves that the exhaust gas emissions, in particular NOx, do not rise above normal operation.

  In order to achieve the equalization of the injection quantity of the intake pipe injection valve in a particularly simple manner, the method comprises at least one lean injection step, one post-injection step, one torque measurement step, and one equalization step Is advantageously included. In the lean injection step, fuel is injected via at least one of the intake manifold injectors such that the synthetic fuel / air mixture is lean. In the post-injection step, the fuel is injected through at least one of the direct injection valves so that the torque of the internal combustion engine generated by combustion does not change. In this case, the amount of fuel in the post-injection step is determined such that the synthetic fuel / air mixture is a theoretical fuel / air mixture. In the torque measurement step, the torque share of at least two cylinders is determined. In the equalization step, at least one injection quantity of the intake pipe injection valve is corrected as a function of the torque share of the plurality of cylinders.

  In the post-injection step, if fuel is injected into at least one cylinder for each exhaust train, this has the special advantage that the fuel / air mixture in each exhaust train is a theoretical fuel / air mixture. is doing. This is particularly advantageous when an exhaust gas catalyst is attached to each exhaust train. Thus, the theoretical fuel / air mixture in each exhaust train prevents NOx emissions from rising.

  When each cylinder has at least one direct injection valve in an internal combustion engine, the method according to the invention is particularly simple when fuel is injected into each cylinder in the post-injection step.

  If the fuel post-injection is injected into one cylinder only every first number of revolutions of the crankshaft, especially every two revolutions, this is the sensitivity of the method. Has the special advantage of being particularly low compared to the metering error (Zumessfehlern) of the direct injection valve. Another advantage is that the amount of fuel to be injected is particularly high, which is also available, for example, when the direct injection valve is formed as a cost-effective solenoid valve.

  Here, if the settable first number is selected as a function of the catalyst state and / or the catalyst temperature and / or the characteristic of the characteristic curve of the direct injector, this ensures that the method always operates. It can be guaranteed.

  Similarly, the post-injection can be shifted to another cylinder after a configurable second number of ignition processes. That is, the post-injection step is executed at least twice. In this case, the first injection is performed directly into the first cylinder, the second injection is performed directly into the second cylinder, There is a second number of ignition process rotations that can be set between the second time. This further improves the exhaust gas mixing.

  In the lean injection step, if the synthetic fuel / air mixture has a λ value in the range of 1.1 to 1.2, this is particularly advantageous to ensure that the method is carried out. Lower λ values reduce the amount of fuel to be injected in the post-injection step, which is not advantageous as it increases the sensitivity of the method to direct injection valve metering errors. Conversely, a very high λ value adversely affects the ignition performance of the fuel / air mixture.

  It is advantageous to perform the post-injection at a crankshaft angle> 40 ° so that the injection in the post-injection step is carried out so that the torque is neutral, i.e. without significant torque share. The method of equalizing the injection amount of the intake pipe injection valve used in the cylinder equalization step is a reference for determining what torque share is allowed. The torque share generated by post-injection must be small so that the cylinder equalization method is not affected in its functionality.

  In order to reduce unwanted emissions, in particular particles, it is particularly advantageous when the injection in the post-injection step is carried out within the range of 120 ° to 140 ° crankshaft angle.

  The drawing shows a particularly advantageous embodiment of the method according to the invention.

FIG. 1 shows a schematic view of a cylinder of an internal combustion engine according to the superordinate concept of claim 1. FIG. 2 shows a configuration diagram of a multi-cylinder internal combustion engine. FIG. 3 shows a flow chart of the method according to the invention.

  FIG. 1 shows a cylinder 10 of an internal combustion engine having a combustion chamber 20 and a piston 30, and the piston 30 is connected to a crankshaft 50 by a connecting rod 40.

  As is known, in the downward movement of the piston 30, air to be burned is sucked into the combustion chamber 20 via the intake pipe 80. The combusted air is discharged from the combustion chamber 20 through the exhaust pipe 90 as the piston 30 moves upward. The amount of air sucked in via the intake pipe 80 is adjusted via the filling change device, ie in this embodiment via the throttle valve 100 whose position is determined by the control device 70.

  Fuel is injected into the air sucked from the intake pipe 80 through the direct injection valve 110 arranged in the combustion chamber 20 and through the intake pipe injection valve 150 arranged in the intake pipe 80. And a fuel / air mixture is generated in the combustion chamber 20. The amount of fuel injected by the direct injection valve 110 and the amount of fuel injected by the intake pipe injection valve 150 are usually determined by the control device 70 via the time length and / or strength of the operation signal. . Spark plug 120 ignites the fuel / air mixture.

  A λ sensor 130 is present in the exhaust pipe 90, which determines the combustion air ratio λ and transmits it to the controller 70. The NOx storage catalyst 140 in the path of the exhaust pipe 90 ensures that the NOx component in the exhaust gas is clearly reduced.

  The intake valve 160 at the connection port of the intake pipe 80 with the combustion chamber 20 is operated by the cam shaft 190 via the cam 180. Similarly, the exhaust valve 170 at the connection port of the exhaust pipe 90 with the combustion chamber 20 is operated by the cam shaft 190 via the cam 182. The cam shaft 190 is coupled to the crank shaft 50. Normally, the camshaft 190 performs one rotation for every two rotations of the crankshaft 50. The combustion cycle is then divided into an intake stroke, a compression stroke, a working stroke and an exhaust stroke, as is known. In this case, the top dead center of the piston 30 is shifted from the compression stroke to the working stroke, or from the exhaust stroke. The transition to the intake stroke is defined, and the bottom dead center of the piston 30 defines the transition from the intake stroke to the compression stroke, or the transition from the working stroke to the exhaust stroke. The crankshaft angle usually represents the relative angular position of the piston with respect to top dead center.

  In the injection of fuel through the intake pipe injection valve 150, the fuel is mixed with the air present therein in the intake pipe 80 to form a fuel / air mixture, and the fuel / air mixture is It is sucked into the combustion chamber 20 in the opened intake stroke. Through the direct injection valve 110, fuel is injected into the combustion chamber 20 at any crankshaft angle. The fuel is first injected through the intake pipe injection valve 150 and then into the fuel / air mixture sucked into the combustion chamber 20 by the downward movement of the piston 30 by another injection through the direct injection valve 110. When the fuel is injected again, the torque transmitted to the crankshaft 50 by the downward movement of the piston 30 in the ignition by the spark plug 120 is a function of the crankshaft angle at which the fuel is injected. If the crankshaft angle is greater than 40 °, the torque generated will not be higher or slightly higher than the torque that would be obtained if no further fuel was injected through the direct injection valve 110. .

  FIG. 2 shows a configuration diagram of the internal combustion engine, and in this embodiment, a configuration diagram of the internal combustion engine having eight cylinders. A first cylinder 10a, a second cylinder 10b, a third cylinder 10c, a fourth cylinder 10d, a fifth cylinder 10e, a sixth cylinder 10f, a seventh cylinder 10g and an eighth cylinder 10h are shown. ing. Each of the eight cylinders 10a, 10b, 10c, 10d, 10e, 10f, 10g, 10h has one direct injection valve 110a, 110b, 110c, 110d, 110e, 110f, 110g, 110h and one intake pipe respectively. Injection valves 150a, 150b, 150c, 150d, 150e, 150f, 150g, and 150h are attached.

  All the cylinders share the intake pipe 80 and the exhaust pipe 90. In this case, not only the intake pipe 80 but also the exhaust pipe 90 is branched into a supply pipe to the cylinder or a discharge pipe from the cylinder. FIG. 2 does not show a branch for each cylinder of the exhaust pipe 90. The exhaust pipes of cylinders 10a, 10b, 10c, 10d, not shown, are combined to form a first exhaust row A. The exhaust pipes of cylinders 10e, 10f, 10g, 10h, not shown, are combined to form a second exhaust row B. The exhaust gas from the first exhaust row A is guided to pass through the first λ sensor 130a, and then the exhaust gas is guided to pass through the second λ sensor 130b. Along with the B exhaust gas, the exhaust gas is discharged through a common exhaust pipe 90.

  The exhaust gas in the exhaust pipe 90 is guided to pass through the NOx storage catalyst 140 (geleitet wird). In order to ensure the functionalization of the NOx storage catalyst, it is necessary that the fuel / air mixture is a theoretical fuel / air mixture. In this case, it is not so important whether the theoretical fuel / air mixture is formed in advance in the combustion chamber 20 or only in the exhaust pipe 90. Such a stoichiometrisches Kraftstoff- / Luft-Verhaltnis is, for example, a lean fuel / air mixture formed in the first cylinder 10a and a rich fuel / air mixture in the second cylinder 10b. Can be generated in the exhaust pipe 90. In this case, however, it is important to pay particular attention to the firing sequence of the cylinders so that a sufficiently good exhaust gas mixture is ensured. If the exhaust gas that is passed through the NOx storage catalyst 140 is alternately rich and lean, this can lead to an exothermic reaction, which can result in a very strong heat load on the NOx storage catalyst 140.

  FIG. 3 shows a flow chart of the method according to the invention. In the embodiment shown as an example, the intake pipe injectors 150a, 150b, 150c, 150d of the first exhaust row A should be equalized. Step 100 represents the start of the method. Step 1010 follows, and in step 1010 it is checked whether the equalization of the intake pipe injection valves 150a, 150b, 150c, 150d of the first exhaust row A has already been performed. If equalization has already been performed, step 1020 follows, and step 1020 ends the method. If equalization has not yet been performed, step 1030 follows.

  In step 1030, a first cylinder is identified for each exhaust train whose intake pipe injection valve is to be calibrated, and in this first cylinder, fuel is then directly injected by the injection valve 110 in a post-injection step 1050. Be injected. For exhaust row A, this is the first cylinder 10a. A lean injection step 1040 follows.

  In the lean injection step 1040, the fuel is introduced into the cylinders 10a, 10b, 10c, 10d via the intake pipe injection valves 150a, 150b, 150c, 150d, and the fuel-air ratio is particularly between 1.1 and 1.2. It is injected so that it is lean at the λ value of. A post injection step 1050 follows.

  In the post-injection step 1050, fuel is injected between the 120 ° and 140 ° crankshaft angles via the first direct injection valve 110a of the first cylinder 10a. In this case, the injection amount is selected so that the theoretical fuel / air mixture is formed in the exhaust pipe 90, that is, the value measured by the first λ sensor 130a takes the value 1.

  The lean injection step 1040 is repeated every two rotations of the crankshaft 50, that is, when the crankshaft 50 makes two rotations, fuel is injected once through each of the four intake pipe injection valves 150a, 150b, 150c, and 150d. Is done. The post injection step 1050 is repeated after the determined first number of rotations of the crankshaft 50. In this embodiment, this number is equal to 2, that is, when the crankshaft 50 makes two revolutions, fuel is injected once through the first direct injection valve 110a.

  The post-injection step 1050 is followed by a torque measurement step 1060. In a torque measurement step 1060, the rotational movement of the crankshaft 50 is measured by an angle sensor not shown in FIG. From the measured rotational motion, the torque share of each of the cylinders 10a, 10b, 10c, 10d is determined. In particular, a very large amount of fuel is injected through any intake pipe injection valve 150a, 150b, 150c, 150d, and a very small amount of fuel is injected through any intake pipe injection valve 150a, 150b, 150c, 150d. Is determined. An equalization step 1070 follows.

  In the equalization step 1070, the operation of the intake pipe injection valve 150, in which it was determined in the torque measurement step 1060 that a very large amount of fuel was injected, is corrected so that the injection amount is reduced. Conversely, the operation of the intake pipe injection valve 150, in which it was determined in the torque measurement step 1060 that a very small amount of fuel was injected, is changed so that the injection amount is increased. Step 1080 follows.

  In step 1080, optionally, after the second number of combustion processes, the first identified cylinder 10 in step 1030 is changed, in which fuel was injected in post-injection step 1050. In this embodiment, after each sixth combustion process, the cylinder is switched to the next cylinder in the same exhaust sequence A ignition sequence. Here, only the combustion process of the same exhaust train A is counted as the combustion process. That is, in this embodiment, specifically, the first cylinder 10a is switched to the second cylinder 10b. That is, in the post-injection step 1050, when the fuel is injected the next time, this is performed in the second cylinder 10b via the second direct injection valve 110b. Step 1090 follows.

  In step 1090, the change in the operation signal of the intake pipe injection valve 150 given in step 1070 may be stored in the control device 70 as a correction value of the operation signal of the intake pipe injection valve 150. Step 1100 follows.

  In step 1100, the correction value of the operation signal of the first intake pipe injection valve 150a calculated in step 1090 is included as an adaptive value of the cylinder equalizing function. It is stored in the control device 70 that the intake pipe injection valves 150a, 150b, 150c, and 150d are equalized. Step 1110 follows.

  Step 1110 ends the method.

  The method shown as an example in this embodiment is naturally applicable to the equalization of the intake pipe injection valves 150e, 150f, 150g, and 150h of the second exhaust row B as well. Similarly, the method according to the invention is equally applicable to an internal combustion engine having any number of exhaust trains, in particular one exhaust train. For example, the method can be applied to an internal combustion engine having two, three, four or six cylinders.

  In the post-injection step 1050, fuel may be injected directly into the more than one cylinder 10 via the injection valve 110. In particular, fuel can be injected into each cylinder 10a, 10b, 10c, 10d via a respective direct injection valve 110a, 110b, 110c, 110d. In this case, step 1030 can be omitted.

  Similarly, it is not always necessary that one direct injection valve 110 be attached to each cylinder 10. For example, it is sufficient that only one cylinder 10 has a direct injection valve 110 for each exhaust train. In this case, in the post-injection step 1050, since the fuel is always injected into this one direct injection valve 110 of each exhaust train, steps 1030 and 1080 can be omitted. Of course, the method can be carried out in any other number of direct injection valves 110 per exhaust train as well.

  Further, it is possible that each cylinder 10 is not provided with an intake pipe injection valve 150. For example, in this embodiment, only the first cylinder 10a and the fourth cylinder 10d can have the intake pipe injection valves 150a and 150d. In this case, only the torque assigned to the cylinders 10a and 10d is determined in the torque measurement step 1060, and only the injection amounts of the intake pipe injection valves 150a and 150d are corrected in the equalization step 1070.

  The rotation of the settable first number of crankshafts 50, after which the post-injection step 1050 is repeated, may be selected in particular by two different methods. In this case, the first settable number is selected as a function of the characteristics of the characteristic curve of the direct injection valve 110, in particular, the state of the NOx storage catalyst 140, the temperature of the NOx storage catalyst 140 and the minimum amount of metering.

  Torque measurement step 1060 and equalization step 1070 substantially correspond to the nature of the cylinder equalization method known from the prior art. The torque measurement in step 1060 can be performed in particular via the measurement of the segment time in the rotation of the crankshaft 50. The equalization in step 1070 is calculated by calculating the torque share of the cylinder to be equalized from the segment time difference measured in step 1060 or from the difference in the injection amount of the intake pipe injection valve 150 to be equalized. Therefore, the difference may be converted into a correction coefficient for the operation of the intake pipe injection valve 150 in the equalizing step 1070, and thereby the torque of the cylinder 10 to be equalized may be performed by pre-control (vorgesteuert erfolgen).・ Share is compensated. However, the equalization in step 1070 may be performed by a cybernetic control algorithm (eg, a PI controller), in which case execution steps 1040, 1050, 1060 and 1070 are then performed by the cylinder 10 to be equalized. It must be repeated until fully equalized.

10, 10a, 10b, 10c, 10d, 10e, 10f, 10g, 10h Cylinder 20 Combustion chamber 30 Piston 40 Connecting rod 50 Crankshaft 70 Controller 80 Intake pipe 90 Exhaust pipe 100 Throttle valve 110, 110a, 110b, 110c, 110d 110e, 110f, 110g, 110h Direct injection valve 120 Spark plug 130, 130a, 130b λ sensor 140 NOx storage catalyst 150, 150a, 150b, 150c, 150d, 150e, 150f, 150g, 150h Intake pipe injection valve 160 Intake valve 170 Exhaust valve 180, 182 Cam 190 Cam shaft 1000 Method start step 1010 Intake pipe injection valve equalization completion inspection step 1020, 1110 Method end step 1030 First cylinder identification step 1040 Inject injection step 1050 Post injection step 1060 Torque measurement step 1070 Equalization step 1080 Cylinder switching step 1090 Storage step of correction value of operation signal of intake pipe injection valve 1100 The correction value is included as an adaptive value of the cylinder equalization function Step

Claims (12)

In a Gleichstellung method of torque share (Drehmomentenbeitrage) of a plurality of intake pipe injection valves (150) of a plurality of cylinders (10) of an internal combustion engine having at least one direct injection valve (110),
Fuel is injected into the cylinder (10) via at least one of the intake pipe injectors (150) such that the synthetic fuel / air mixture is lean, and the fuel is injected directly into the injector (110). Via at least one, this makes no contribution to the torque of the internal combustion engine and the synthetic fuel / air mixture (resultierende Kraftstoff- / Luft-Gemisch) is injected as a stochiometrisch fuel / air mixture A method of equalizing torque share of a plurality of intake pipe injection valves of a plurality of cylinders. A lean injection step (1040) in which fuel is injected into the cylinder (10) via at least one of the intake manifold injectors (150) such that the synthetic fuel / air mixture is lean;
After the fuel is injected via at least one of the direct injection valves (110), so that no contribution is made to the torque of the internal combustion engine and the synthetic fuel / air mixture is a theoretical fuel / air mixture. Injection step (1050);
A torque measurement step (1060) in which the torque share of at least two cylinders is determined;
An equalization step (1070) in which at least one injection quantity of the intake pipe injection valve (150) is corrected as a function of the torque share of the at least two cylinders (10);
The equalization method according to claim 1, comprising: 3. The equalizing method according to claim 2, wherein in the post-injection step (1050), fuel is injected into at least one cylinder (10) for each exhaust train (A). 4. The cylinder (10) according to claim 3, characterized in that each cylinder (10) has at least one direct injection valve and in the post-injection step (1050) fuel is injected into each cylinder (10). Equalization method. In the post-injection step (1050), for each exhaust train (A), fuel is only delivered into one cylinder (10) for every first settable rotation of the crankshaft, in particular every two rotations. The equalizing method according to claim 2, wherein the equalizing method is performed. 6. The settable first number is selected as a function of at least one of a catalyst state and a catalyst temperature and a characteristic curve of a direct injection valve (110) (Charakteristik einer Kennlinie). The equalization method described in. A post-injection step (1050) is performed at least one first time and at least one second time, in which case at least one second number of ignition process rotations configurable between the first and second times 5. The fuel injection system according to claim 2, wherein the first injection is performed directly into the first cylinder (10 a) and the second injection is performed directly into the second cylinder (10 b). The equalization method described in any one. 8. The equalizing method according to claim 2, wherein, in the lean injection step (1040), the synthetic fuel / air mixture has a λ value in the range of 1.1 to 1.2. In the post-injection step (1050), fuel is injected via a direct injection valve (110) at a crankshaft angle in the range of 120 ° to 140 ° after top dead center of the attached cylinder (10). 9. The equalization method according to claim 2, wherein the equalization method is performed. A computer program, characterized in that it is programmed for use in the equalization method according to any of claims 1-9. 10. An electrical storage medium for an operating / control device (70) of an internal combustion engine, on which is stored a computer program for use in the equalization method of any of claims 1-9. 10. An operating / control device (70) for an internal combustion engine, characterized in that it is programmed for use in the equalization method according to any of claims 1-9.

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