Method for controlling an internal combustion engine, internal combustion engine and motor vehicle with an internal combustion engine

Abstract

Method for controlling an internal combustion engine (12), in particular a gasoline engine of a motor vehicle (10), comprising the following steps: a) setting the combustion air ratio (λ) of the air / fuel mixture supplied to the internal combustion engine (12) to a first value (w1) for a first time interval (34), the first value (w1) resulting in a rich air / fuel mixture, b) subsequently masking out at least one cylinder (22) of the internal combustion engine (12), and c) increasing the combustion air ratio (λ) to a second value (w2) for a second time interval (36) while the at least one cylinder (22) is masked out, wherein the second time interval (36) immediately follows the first time interval (34).

Description

[0001] The invention relates to a method for controlling an internal combustion engine, an internal combustion engine and a motor vehicle with an internal combustion engine.

[0002] To increase the sportiness of motor vehicles with internal combustion engines, especially gasoline engines, the goal is to achieve increasingly shorter gear shifts between two gears. This minimizes the time the vehicle is idle during gear changes.

[0003] To reduce the duration of gear shifts in automatic transmissions, a technique known as individual cylinder suppression is used. This technique suppresses fuel injection into individual cylinders shortly before and during gear shifting. As a result, no combustion takes place in the suppressed cylinder, temporarily reducing the engine's speed and torque. This reduction in speed and torque leads to a reduction in gear shift time.

[0004] However, with single-cylinder suppression, the piston of the suppressed cylinder moves further, forcing more fresh air and thus more oxygen through the exhaust system. This increases the oxygen input to the catalytic converter while a cylinder is suppressed. However, the excess oxygen alters the conversion of pollutants at the catalytic converter, which is a three-way catalytic converter.

[0005] US 2015 / 0 184 599 A1 discloses a method for reducing torque in an internal combustion engine of a vehicle by masking out at least one cylinder during a gear shift.

[0006] DE 10 2005 005 537 A1 describes a fuel cut-off control unit for an internal combustion engine and a control device for carrying out a fuel increase correction after a fuel cut-off.

[0007] DE 10 2013 218 191 A1 describes a hybrid vehicle with a control system that controls the time required for engine shutdown.

[0008] DE 10 2016 103 909 A1 discloses a method and a system for monitoring an imbalance of the air-fuel ratio during an overrun fuel cut.

[0009] DE 11 2011 105 110 B4 describes a device for detecting an imbalance anomaly in an air-fuel ratio between cylinders in a multi-cylinder internal combustion engine.

[0010] It is therefore an object of the invention to provide a method for controlling an internal combustion engine, an internal combustion engine and a motor vehicle with an internal combustion engine, in which the changed conversion of pollutants during the individual cylinder suppression is counteracted.

[0011] The object is achieved by a method for controlling an internal combustion engine, in particular a gasoline engine of a motor vehicle, with the following steps: a) adjusting the combustion air ratio of the air / fuel mixture supplied to the combustion engine to a first value for a first time interval, the first value resulting in a rich air / fuel mixture, b) subsequently masking out at least one cylinder of the internal combustion engine, and c) increasing the combustion air ratio to a second value for a second time interval during which at least one cylinder is masked out, wherein the second time interval immediately follows the first time interval.

[0012] By changing the combustion air ratio before a cylinder is deactivated, it is possible to prepare and thus precondition the catalyst for the excess oxygen during cylinder deactivation. This can reduce or completely compensate for the altered pollutant conversion during the duration of the individual cylinder deactivation. Because the initial value results in a rich air / fuel mixture, it is ensured that the full oxygen storage capacity of the catalyst is restored during the initial time interval. The catalyst is preferably a three-way catalyst, especially one with an oxygen storage device.

[0013] The method can also be seen as a method for controlling an assembly consisting of an internal combustion engine, a catalytic converter and a transmission, in particular an automatic transmission.

[0014] For example, the second value is greater than the first, so less oxygen is available during the first time interval. This consumes the oxygen stored in the catalyst, and the catalyst thus reaches its full oxygen storage capacity. Therefore, it can absorb the excess oxygen during the duration of the single-cylinder suppression.

[0015] The start of individual cylinder suppression can occur immediately after the first time interval. Individual cylinder suppression can also occur precisely during the second time interval.

[0016] Preferably, an upcoming gear change is performed while at least one cylinder is deactivated, thereby enabling a rapid gear change. The second time interval can correspond to the duration of the gear change of the transmission used, which is in particular an automatic transmission.

[0017] To avoid unnecessary changes in the combustion air ratio, the upcoming gear change can be detected and then step a) executed. This is possible because the automatic transmission has a certain latency between requesting a gear change and executing the gear change. The first time interval can correspond to this latency. This eliminates the need for complex gear changes to be anticipated before they are requested.

[0018] In one embodiment of the invention, the first value is less than 0.97 and is in particular approximately 0.9.

[0019] For example, during normal operation of the internal combustion engine, the combustion air / fuel ratio is set to a standard value that, in particular, results in a stoichiometric air / fuel mixture and / or is between 0.97 and 1.03, particularly preferably approximately 1. This ensures that during normal operation of the internal combustion engine, the catalyst is operated in such a way that the conversion of pollutants is optimized. No switching operations occur during normal operation.

[0020] To reduce pollutant emissions, the second value is between 0.97 and 1.03, in particular around 1, is equal to the normal value and / or results in a stoichiometric air / fuel mixture.

[0021] In one embodiment of the invention, at least two cylinders are masked out, in particular at least partially simultaneously. This allows for even faster switching times. One cylinder can be masked out first, and then, while the first cylinder is masked out, the second cylinder can be masked out to enable gradual masking.

[0022] In one embodiment of the invention, after the second time interval, the combustion air ratio is reduced to a third value for a third time interval. In this way, the oxygen storage capacity of the catalyst can be restored after the oxygen excess during the second time interval. The catalyst's oxygen storage is thus at least partially emptied. This ensures optimal operation of the catalyst after the individual cylinder suppression. This process is also referred to as purging the catalyst.

[0023] The third value can be less than 0.97 and / or less than the first value to ensure optimal catalyst cleanout. The third value can also be equal to the first value.

[0024] In one embodiment of the invention, the internal combustion engine has multiple cylinder banks, wherein, in the first time interval, the combustion air ratio for the cylinder bank containing the at least one cylinder that is masked out in the second time interval is set to the first value. This ensures that, if multiple catalysts are present, the correct catalyst is preconditioned.

[0025] The object is further achieved by an internal combustion engine with a plurality of cylinders and an engine control system, wherein the engine control system is configured to carry out the method according to the invention.

[0026] It is also conceivable that an assembly consisting of the combustion engine, transmission and, if applicable, the catalytic converter is controlled by the engine control unit.

[0027] Furthermore, the object is achieved by a motor vehicle having an internal combustion engine and a transmission, in particular an automatic transmission. The motor vehicle may optionally have a catalytic converter, in particular a three-way catalytic converter with an oxygen storage device.

[0028] Further features and advantages of the invention will become apparent from the following description and the accompanying drawings, to which reference is made. In the drawings: - Fig. 1 schematically shows a motor vehicle according to the invention with an internal combustion engine according to the invention, and - Fig. 2 a diagram which relates the combustion air ratio, the duration of the individual cylinder suppression and a gear change during the implementation of the method according to the invention.

[0029] Fig. 1 schematically shows a motor vehicle 10 with an internal combustion engine 12, two exhaust lines 14, two catalytic converters 16, which are, for example, three-way catalytic converters with oxygen storage, a transmission 18 and an engine control unit 20.

[0030] The internal combustion engine 12 is in particular a gasoline engine and has a plurality of cylinders 22 arranged in two cylinder banks 24.

[0031] Each of the exhaust lines 14 is assigned to one of the cylinder banks 24 and discharges the exhaust gas generated by the cylinders 22 of the corresponding cylinder bank 24.

[0032] One of the catalysts 16 is provided in each of the exhaust lines 14, so that each of the cylinder banks 24 is assigned a catalyst 16.

[0033] The transmission 18, which may be an automatic transmission, is connected to the internal combustion engine 12 via the output shaft 26 of the internal combustion engine 12 for transmitting the torque generated by the internal combustion engine 12.

[0034] On the output side, the transmission 18 is connected to the wheels (not shown) of the motor vehicle 10.

[0035] The engine control 20 is connected in terms of information technology, for example via suitable cabling such as a bus system, both to the combustion engine 12 and to the transmission 18 and the catalytic converters 16.

[0036] The engine control unit 20 controls, for example, the combustion air ratio λ of the air / fuel mixture supplied to the combustion engine 12, sends and receives shift requests from the transmission 18 and receives measured values ​​from a lambda probe of the catalytic converters 16.

[0037] The engine control unit 20 can also control the fuel supply and the ignition of the individual cylinders 22 in such a way that individual cylinders 22 are masked out, i.e., no fuel is supplied to the corresponding cylinder 22 for a certain number of revolutions and the ignition is switched off.

[0038] The process of a fast switching process with single cylinder suppression and optimized pollutant emissions is in Fig. 2, in which three curves are shown, each representing the temporal progression of a process.

[0039] The lower curve 28 indicates whether the transmission 18 is performing a gear shift, the middle curve 30 indicates the number of cylinders 22 that are suppressed by individual cylinder suppression at a specific time, and the upper curve 32 indicates the value of the combustion air ratio λ, also called lambda value, over time.

[0040] The timing of a gearshift by the transmission 18 is shown, with four vertical dashed lines distinguishing different time intervals. The earliest and latest time intervals, visible on the left and right edges, represent normal operation N of the internal combustion engine 12 and the motor vehicle 10, respectively.

[0041] During normal operation N, no gear shifts of the transmission 18 take place. The internal combustion engine 12 or the motor vehicle 10 is thus between, before, or after a gear shift.

[0042] During normal operation N, the combustion air ratio λ of the air / fuel mixture supplied to the combustion engine 12 is set by the engine control unit 20 to a normal value n, which is approximately 1 (λ = 1). The air / fuel mixture is therefore stoichiometric. This range can vary, for example, between 0.97 and 1.03.

[0043] At time t1, an impending gear change is detected by the engine control unit 20.

[0044] This can be done either by the driver of the motor vehicle 10 requesting a gear change, for example by means of shift paddles, or the engine control 20 determines that a gear change is appropriate based on the operating data of the internal combustion engine 12, the vehicle speed and / or other parameters.

[0045] At this time t1, normal operation N is exited and a first time interval 34 begins.

[0046] At time t1, the transmission 18 also receives the shift request either from the engine control 20 or otherwise and initiates the shift process, as can be seen in the lower curve 28.

[0047] However, the transmission 18 has a certain latency time that the transmission 18 needs before it can perform the actual gear change.

[0048] This latency period extends until a second time t2, at which the first time interval 34 ends and a second time interval 36 begins.

[0049] The first time interval 34 thus corresponds to the latency time of the transmission 18, which is, for example, approximately 200 ms.

[0050] The second time interval 36 can directly follow the first time interval 34.

[0051] From time t2, the pending gear change is carried out by transmission 18.

[0052] At time t3, the pending gear change is completed and the gear shifting process is finished, as can be seen in the lower curve 28.

[0053] The second time interval 36 thus corresponds to the duration of the gear change.

[0054] During gear shifting, the engine control unit 20 performs individual cylinder deactivation for two cylinders 22, meaning that two cylinders 22 are deactivated. This occurs in stages, meaning that first one cylinder 22 is deactivated, followed by a second cylinder 22.

[0055] The two cylinders 22 remain masked out until time t3, i.e. for the entire second time interval 36 or almost the entire second time interval 36, as can be seen in the middle curve 30.

[0056] At time t3, the engine control unit 20 supplies fuel to the two cylinders 22 that were switched off and switches the ignition back on.

[0057] From time t3 onwards, all cylinders 22 of the combustion engine 12 are reactivated and participate in torque generation.

[0058] The two cylinders 22 that are hidden either both belong to the same cylinder bank 24 or one cylinder 22 is hidden in each cylinder bank 24.

[0059] During the second time interval 36, due to the individual cylinder deactivation, there is an oxygen excess at one or both catalysts 16, depending on whether the deactivated cylinders 22 are distributed over one or both cylinder banks 24.

[0060] For the sake of simplicity, reference is made below only to one of the catalysts 16, whereby this means both catalysts 16 in the case where the two hidden cylinders 22 are located on different cylinder banks 24.

[0061] In order for the corresponding catalyst 16 to be able to absorb the excess oxygen during the second time interval 36, it is prepared or preconditioned for this purpose in the first time interval 34.

[0062] This is done by the engine control 20 changing the combustion air ratio λ from time t1.

[0063] During the first time interval 34, the engine control unit 20 controls the internal combustion engine 12 such that the combustion air ratio λ is reduced from the normal value n to a first value w1. This results in a rich air / fuel mixture. The combustion air ratio λ is maintained at the first value w1 for the duration of the first time interval 34.

[0064] The first value w1 is less than 0.97 and is around 0.9 in the example shown, so that the air / fuel mixture is now enriched, i.e. less oxygen is available.

[0065] Due to the richer mixture, there is a lack of oxygen in the catalytic converter 16 during the first time interval 34. This is compensated for by the catalytic converter 16 releasing oxygen stored in the catalytic converter 16, so that the conversion of pollutants continues within the optimal range.

[0066] At the same time, the oxygen storage of the catalyst 16 is emptied so that it can store oxygen again, i.e. its oxygen storage capacity increases.

[0067] The combustion air ratio is changed by the engine control unit 20 only for the cylinders 22 of the cylinder bank 24 to which at least one cylinder 22 belongs that is masked out during the gear change in the second time interval 36.

[0068] If the exhaust gas lines 14 of both cylinder banks 24 are combined in front of the catalytic converter 16, i.e., only one catalytic converter 16 is provided for both cylinder banks 24, it is irrelevant which or whether both cylinder banks 24 receive a modified combustion air ratio λ.

[0069] At time t2, the oxygen storages of the catalyst 16 are preferably emptied and the catalyst 16 has reached its full oxygen storage capacity.

[0070] The engine control unit 20 then changes the combustion air ratio λ again at time t2, this time to a second value w2, which lies between 0.97 and 1.03. This results in a stoichiometric air / fuel mixture. In the illustrated embodiment, the second value w2 is equal to the standard value n.

[0071] Although the combustion air ratio λ is back in a normal range, air, and therefore also oxygen, is transported into the exhaust system 14 through the two hidden cylinders 22, so that there is an oxygen surplus at the catalyst 16.

[0072] The catalyst 16 can absorb the excess oxygen because it has its full oxygen storage capacity. This was finally restored in the first time interval 34.

[0073] As a result, pollutant conversion is also operated in the optimal range in the second time interval 36, so that pollutant emissions are not increased despite individual cylinder suppression.

[0074] At time t3, the oxygen storages of the catalyst 16 are filled again.

[0075] In order to empty the oxygen storage of the catalyst 16 again after a switching operation, the catalyst 16 can be cleared, i.e. its oxygen storage can be emptied, in a third time interval 38, which begins, for example, at time t3 and ends at a later time t4.

[0076] For this purpose, the engine control 20 sets the combustion air ratio λ to a third value w3.

[0077] The third value w3 is less than 0.97 and, in the illustrated example, is also less than the first value w1. However, it can also be equal to the first value w1.

[0078] This again creates an oxygen deficiency at the corresponding catalyst 16, causing the catalyst 16 to release oxygen from its oxygen storages. This empties the oxygen storages without pollutant conversion occurring outside the optimal range.

[0079] At time t4, the engine control 20 resets the combustion air ratio λ to the normal value n, so that the internal combustion engine 12 is back in normal operation N from time t4.

[0080] The change in the combustion air ratio λ at time t4 can be calculated as in Fig. 2 can also be done via a ramp, so that there is no abrupt jump in the combustion air ratio λ.

[0081] It is of course possible that the other changes in the combustion air ratio do not occur abruptly, but gradually via a ramp.

Claims

[1] Method for controlling an internal combustion engine (12), in particular a gasoline engine of a motor vehicle (10), comprising the following steps: a) setting the combustion air ratio (λ) of the air / fuel mixture supplied to the internal combustion engine (12) to a first value (w1) for a first time interval (34), the first value (w1) resulting in a rich air / fuel mixture, b) subsequently masking out at least one cylinder (22) of the internal combustion engine (12), and c) increasing the combustion air ratio (λ) to a second value (w2) for a second time interval (36) while the at least one cylinder (22) is masked out, wherein the second time interval (36) immediately follows the first time interval (34). [2] Method according to claim 1, characterized by that an upcoming gear change is carried out while at least one cylinder (22) is masked out. [3] Method according to claim 2, characterized by that the upcoming gear change is detected and then step a) is carried out. [4] Method according to one of the preceding claims, characterized by that the first value (w1) is less than 0.97, in particular approximately 0.

9. [5] Method according to one of the preceding claims, characterized by that the combustion air ratio (λ) during normal operation (N) of the internal combustion engine (12) is set to a normal value (n) which in particular leads to a stoichiometric air / fuel mixture and / or is between 0.97 and 1.03, particularly preferably approximately 1. [6] Method according to one of the preceding claims, characterized by that the second value (w2) is between 0.97 and 1.03, in particular around 1, is equal to the normal value and / or results in a stoichiometric air / fuel mixture. [7] Method according to one of the preceding claims, characterized bythat at least two cylinders (22) are masked out, in particular at least partially simultaneously. [8] Method according to one of the preceding claims, characterized by that after the second time interval (36) the combustion air ratio (λ) is reduced to a third value (w3) for a third time interval (38). [9] Method according to one of the preceding claims, characterized by that the internal combustion engine (12) has a plurality of cylinder banks (24), wherein in the first time interval (34) the combustion air ratio (λ) for the cylinder bank (24) is set to the first value ( W1 ) in which the at least one cylinder (22) is located which is masked out in the second time interval (36). [10] Internal combustion engine with a plurality of cylinders (22) and an engine control (20), wherein the engine control (20) is configured to carry out the method according to one of the preceding claims. [11] Motor vehicle with an internal combustion engine (12) according to claim 10 and a transmission (18), in particular an automatic transmission.

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