DE102011004824B3 - Method for operating internal combustion engine of motor car, involves performing specific diagnosis relative to pollutant emissions of motor car within predetermined operating range of engine upon fulfillment of predetermined condition - Google Patents

Abstract

The method involves arranging an exhaust gas probe (41) with jump probe characteristics in an exhaust system (40). A crankshaft angle sensor (22) is provided for providing measured signal representing crank angle of crankshaft. The specific diagnosis is performed with respect to pollutant emissions of motor car within predetermined operating range of the engine upon fulfillment of predetermined condition, during respective plateau phase of the actuating signal of lambda control. An independent claim is included for device for operating internal combustion engine of motor car.

Description

The invention relates to a method and a device for operating an internal combustion engine having a plurality of cylinders, which are associated with respective injectors for metering fuel, and an exhaust probe with a jump probe characteristic which is arranged in an exhaust tract and whose measurement signal is characteristic for the air / fuel ratio in the respective cylinder and a crankshaft angle sensor whose measurement signal is representative of a crankshaft angle of a crankshaft.

Within the framework of strict legal regulations regarding the pollutant emissions emitted by motor vehicles, an important measure is to minimize emissions of pollutants which occur during the combustion of the air / fuel mixture in the respective cylinder of the internal combustion engine. A further measure is also to be used in internal combustion engines exhaust aftertreatment systems, which convert the pollutant emissions that are generated during the combustion process of the air / fuel mixture in the respective cylinder into harmless substances. For this purpose, catalytic converters are used, which convert carbon monoxide, hydrocarbon and nitrogen oxides into harmless substances.

Both the targeted influencing of the generation of the pollutant emissions during combustion and the conversion of the pollutant components with a high efficiency by the exhaust gas catalyst require a very precisely adjusted air / fuel ratio in the respective cylinder.

Especially in connection with an increasingly close-coupled arrangement of the catalytic converters and also with regard to specific statutory provisions in individual countries, a cylinder-specific precise adjustment of the air / fuel ratio is increasingly important because the individual exhaust packages only relatively poor due to the short mixing distance mix.

Increasingly stringent legislation on the emission of limited pollutants makes it necessary to allow a low air / fuel ratio between the individual cylinders. A large unequal distribution and a waiver of compensation lead to significant emissions deterioration or even noticeable driveability problems.

In addition, there are legal requirements to gradually detect the cylinder-selective unequal distribution in the air / fuel ratio, which leads to the exceeding of specified emission limit values, based on the vehicle fleet of the respective manufacturers in an increasing proportion of the respective vehicles.

For the purpose of a cylinder-specific precise adjustment of the respective air / fuel ratio in the respective combustion chambers of the respective cylinder, it is from the DE 10 2005 009 101 B3 It is known to detect a measurement signal of an exhaust gas probe relative to a reference position of the piston of the respective cylinder and to assign it to the respective cylinder at a predetermined sampling crankshaft angle. By means of a respective controller, a controller value for influencing the air / fuel ratio in the respective cylinder is determined as a function of the measurement signal detected for the respective cylinder. Upon satisfaction of predetermined first conditions including a first temperature range of a temperature representative of a temperature of the respective injector and including a quasi-steady state operation, a first adaptation value is determined in response to the controller value.

Upon satisfaction of predetermined second conditions including a predetermined second temperature range of the temperature representative of the temperature of the respective injector and including a quasi-steady state operation, a second adaptation value is determined in dependence on the controller value.

A correction value for influencing the air / fuel ratio in the respective cylinder is determined as a function of the first and / or second adaptation value as a function of the temperature which is representative of the temperature of the respective injection valve.

From the DE 10 2004 004 291 B3 It is known to use a cylinder-specific lambda control, by means of which the individual deviations of the respective cylinder-specific air / fuel ratios are to be minimized to a mean air / fuel ratio. A measurement signal of an exhaust gas probe arranged in an exhaust tract, which is characteristic for the air / fuel ratio in the respective cylinder, is detected at a predetermined crankshaft angle relative to a reference position of the piston of the respective cylinder and assigned to the respective cylinder. By means of the cylinder-individual lambda controller, a manipulated variable for influencing the air / fuel ratio in the respective cylinder is generated as a function of the measurement signal generated for the respective cylinder. The predetermined crankshaft angle is adjusted depending on an instability criterion of the controller.

From the DE 10 2006 026 390 A1 is an electronic control device for controlling the internal combustion engine in a motor vehicle with a Laufunruheermittlungseinheit and with a Einspritzmengenkorrektureinheit known, wherein a defined group of cylinders is associated with a lambda probe. The injection quantity correction unit is configured such that the injection quantity of a cylinder of the defined group to be examined is adjustable in the lean direction by a difference adjustment value assigned to a run-out difference value and the injection quantity of at least one of the remaining cylinders associated with the same lambda probe is correspondingly adjustable in the direction of grease, thus Overall, a predetermined lambda value of this group, preferably a lambda value of at least almost 1, is achieved. The injection amount correction unit is further configured such that a cylinder-individual Differenzverstellwert for each cylinder of the defined group is adjustable in this way and that cylinder-individual correction values can be determined by the cylinder-individual Differenzverstellwerte be set in relation to each other.

In the DE 103 04 242 B3 a method for determining a parameter of combustion in a second cylinder of a multi-cylinder internal combustion engine is described, wherein a first cylinder to a first channel of the exhaust system and the second cylinder is connected to a second channel of the exhaust system. In the first channel, a lambda probe is arranged and a rough running of the internal combustion engine between the first and the second cylinder is monitored. The parameter of the combustion in the second cylinder is estimated by the signal of the lambda probe when no significant rough running between the burns in the first and second cylinders has been detected. By this method, it is possible to reduce the number of lambda probes.

The object underlying the invention is to provide a method and a device for operating an internal combustion engine, which enables a particularly reliable operation of the internal combustion engine.

The object is solved by the features of the independent claims. Advantageous embodiments of the invention are characterized in the subclaims.

The invention is characterized by a method and a corresponding device for operating an internal combustion engine having a plurality of cylinders, which are associated with respective injectors for metering fuel, and an exhaust probe with jump probe characteristic, which is arranged in an exhaust tract and whose measurement signal is characteristic of the air / Fuel ratio in the respective cylinder, a crankshaft angle sensor whose measurement signal is representative of a crankshaft angle of a crankshaft. Within a predetermined operating range of the internal combustion engine, a cylinder-specific diagnosis with respect to pollutant emissions is carried out upon fulfillment of at least one predetermined condition.

The predetermined condition may be met, for example, at a predetermined quasi-stationary operating state and / or after a predetermined period of time or route.

During the execution of the cylinder-specific diagnosis, the diagnosis is actively carried out only during a respective plateau phase of a control signal of a lambda control. The control signal of the lambda control in the case of an exhaust probe with a jump probe characteristic initially has a linear rising profile, followed by the plateau phase followed, which is then completed by a jump. At the jump, a linear reduction of the control signal then turns until it is followed again by a plateau phase, which in turn is followed by an opposite jump of the control signal. This process is then repeated. The linear rise of the control signal and also the linear descent of the control signal is caused by an I component of the lambda controller. The jump is also called a so-called P-jump and is caused by a P-part of the lambda controller. The respective plateau phase is in each case started in time correlated to a detection of a stoichiometric air / fuel ratio by the exhaust gas probe with jump characteristic.

The control signal of the lambda control influences a fuel mass to be metered and thus a triggering of the respective injection valve.

By actively performing the diagnosis only during a respective plateau phase of the control signal of the lambda control, a contribution can easily be made to setting a uniform air / fuel ratio for all the cylinders associated with the exhaust gas probe, namely with regard to the influence of the control signal of the lambda control , In this way, a contribution is thus made that, caused by the actuating signal during a respective section with active diagnosis, no cylinder-selective injection change takes place and thus a possible disruption caused thereby is substantially excluded and thus the quality of the diagnosis is influenced very positively.

According to an advantageous embodiment, a duration of the respective plateau phase of the control signal of the lambda control is extended during the diagnosis such that it is longer than a working cycle or a predetermined multiple of working cycles. In this way, it can be easily ensured that, influenced by the actuating signal, all the cylinders for the working cycle or the predetermined multiple of working cycles are subjected to the same air / fuel ratio to be set. Thus, such nondeterministic influences can be avoided particularly efficiently and thus the quality of the diagnosis can be influenced very positively.

According to an advantageous embodiment, the duration of the plateau phase of the control signal of the lambda control is set as a function of a maximum oxygen storage capacity of an exhaust gas catalytic converter during the diagnosis. In this way, it is easy to make a contribution to keeping the pollutant emissions as low as possible during the diagnosis.

According to a further embodiment, the diagnosis comprises a running-trouble-based, cylinder-specific diagnosis with regard to pollutant emissions.

According to a further embodiment, the diagnosis comprises a cylinder-specific lambda control.

By performing the Laufunruhebasierten individual cylinder diagnosis with respect to pollutant emissions can be detected early on exceeding pollutant emissions, especially over a permissible range. If the diagnosis comprises carrying out the cylinder-specific lambda control, for example, a component-based diagnosis can also take place. For example, it is possible to detect a faulty injection valve which has, for example, a coked nozzle needle or also deposits on the injection valve, which lead to a deterioration of the injection.

As part of the running trouble-based, cylinder-specific diagnosis, for example, an active adjustment of the air / fuel ratio in the respective cylinders takes place. Thus, for example, the air / fuel ratio of the cylinder to be analyzed is gradually being increasingly adjusted toward lean, with the respective other cylinders corresponding compensation being carried out by correspondingly opposite adjustment of the air / fuel ratio. Such a change of the respective air / fuel ratio is preferably carried out until a rough running value has reached or exceeded a predetermined threshold value.

The diagnosis can then take place, for example, via the adjusted adjustment signal for the respective cylinder, which for example can also be representative of an offset injection quantity, and comparing this with a reference value, for example the average value of the respective cylinders when carrying out the diagnosis for the individual cylinder corresponds. With a correspondingly high deviation, such as over 25%, it is then possible to conclude that an emission-relevant error has occurred and appropriate measures can be initiated.

Embodiments of the invention are explained in more detail below with reference to the schematic drawings. Show it:

1 an internal combustion engine with a control device,

2 a flowchart of a program for operating the internal combustion engine and

3A . 3B Charts in which a given forced-air / fuel ratio to be set is plotted over time.

Elements of the same construction and / or function are identified across the figures with the same reference numerals.

An internal combustion engine ( 1 ) comprises an intake tract 1 , an engine block 2 , a cylinder head 3 and an exhaust tract 4 , The intake tract 1 preferably includes a throttle 11 and a collector 12 and suction pipe 13 leading to a cylinder Z1 via an inlet passage in the engine block 2 is guided. The engine block 2 further comprises a crankshaft 21 , which has a connecting rod 25 with a piston 24 of the cylinder Z1 is coupled.

The cylinder head 3 includes a valvetrain with a gas inlet valve 30 , a gas outlet valve 31 and valve actuators 32 . 33 , The cylinder head 3 further comprises an injection valve 34 and a spark plug 35 , Alternatively, the injection valve 34 also in the intake tract 1 be arranged.

The exhaust tract 4 includes an exhaust gas catalyst 40 , which is preferably designed as a three-way catalyst.

A control device 6 is provided, the sensors are assigned, which detect different measured variables and the measured values of Determine measured quantity. Operating variables include not only the measured variables but also derived from these variables.

The control device 6 controls depending on at least one of the operating variables, the actuators, which are assigned to the internal combustion engine, and which each corresponding actuators are assigned, by generating control signals for the actuators.

The control device 6 may also be referred to as a device for operating the internal combustion engine.

The sensors are a pedal position transmitter 71 , which indicates the position of an accelerator pedal 7 captured, an air mass meter 14 , which is an air mass flow upstream of the throttle 11 detected, a temperature sensor 15 , which detects an intake air temperature, a pressure sensor 16 , which detects the intake manifold pressure, a crankshaft angle sensor 22 which detects a crankshaft angle to which a rotational speed N is then assigned, a torque sensor 23 , which is a torque of the crankshaft 21 detected, a camshaft angle sensor 36a which detects a camshaft angle and an exhaust gas probe 41 which detects a residual oxygen content of the exhaust gas and whose measurement signal is characteristic of the air / fuel ratio in the cylinder Z1 in the combustion of the air / fuel mixture. The exhaust gas probe 41 is preferably designed as a binary lambda probe and thus has a measurement signal with jump characteristic. The jump of the measurement signal takes place in a narrow range around the stoichiometric air / fuel ratio.

Depending on the embodiment, any subset of said sensors may be present or additional sensors may also be present.

The actuators are, for example, the throttle 11 , the gas inlet and outlet valves 30 . 31 , the injection valve 34 or the spark plug 35 ,

In addition to the cylinder Z1 also more cylinders Z2 to Z4 are provided, which then also corresponding actuators are assigned. Preferably, each exhaust bank on cylinders, which can also be referred to as a cylinder bank, in each case an exhaust gas line of the exhaust gas tract 4 assigned and the respective exhaust line each an exhaust gas probe 41 assigned accordingly.

The control device 6 preferably comprises a computing unit and a memory for storing data and programs. To operate the internal combustion engine is in the control device 6 stored a program for operating the internal combustion engine, which can be processed during operation in the arithmetic unit and which is designed to perform a cylinder-specific diagnosis of pollutant emissions upon fulfillment of at least one predetermined condition. The program is, for example, in a step S1 ( 2 ), for example, timely to a start of the internal combustion engine.

In a step S3, it is checked whether a predetermined condition is met. The predetermined condition can be met, for example, if a quasi-stationary operating state is present and / or a predetermined time has elapsed since the last time the condition was fulfilled and / or a predefined route has been traveled since the last time the condition was fulfilled.

If the condition of step S3 is not fulfilled, step S3 is carried out again, if appropriate after a predetermined waiting period.

If, on the other hand, the condition of step S3 has been met, switching to the lambda control with modified stopping times takes place in a step S5. That is, the plateau phase of the control signal of the lambda control is adapted for the diagnosis. It is thus preferably extended and indeed in such a way that it is longer than a working game or a predetermined multiple of working games. The diagnosis is then carried out in this case only active during the work cycle or the predetermined multiple of working games.

In a step S7, it is then checked whether a defined predetermined stopping time, which can also be referred to as the duration T9, T11 of the plateau phase, is present in the rich or lean range. If this is not the case, the processing, if necessary after a predetermined waiting period, is continued again in step S7.

If, on the other hand, the condition of step S7 is met, the diagnosis is generally activated. Active, the diagnosis is then carried out only during the respective plateau phase of the control signal of the lambda control and in particular also carried out depending on the predetermined duration T9, T11 the plateau phase for a work cycle or the predetermined multiple of working cycles.

In a step S11, it is checked whether the diagnosis is completed. If this is the case, the lambda control is switched over to nominal stopping times in a step S13, that is to say to the times T1, T3, T5, T7 of the plateau phase which are predetermined outside the diagnosis.

If, on the other hand, the condition of step S11 is not satisfied, it is checked in a step S15 whether the defined stopping time has ended. If this is not the case, the processing is continued again in step S11, if appropriate after a predetermined waiting time has elapsed.

If, on the other hand, the condition of step S15 is satisfied, the diagnosis is stopped in a step S17, that is to say the diagnosis is temporarily not continued actively. Subsequent to step S17, the processing in step S7 is continued.

In the 3A and 3B the curve SSV of the control signal of the lambda control is plotted over the time t. In the 3A the course SSV of the control signal is plotted for an operation outside the diagnosis and in the 3B the course SSV of the actuating signal is shown for the operation during the diagnosis.

T1 to T11 denote the respective durations of the plateau phases. With N is in the 2A and 2 B denotes a respective neutral value of the control signal of the lambda control. Thus, when the control signal has the neutral value N, the control signal does not influence the air / fuel ratio to be set in the respective cylinder Z1 to Z4. Accordingly, when the control signal assumes a value not equal to the neutral value N, influencing with respect to enrichment or correspondingly leaning of the mixture in the respective cylinders Z1 to Z4 takes place.

Claims (6)

Method for operating an internal combustion engine having a plurality of cylinders (Z1 to Z4), to which respective injection valves ( 34 ) are assigned for metering fuel, and an exhaust gas probe ( 41 ) with a jump probe characteristic in an exhaust tract ( 40 is arranged and whose measurement signal is characteristic of the air / fuel ratio in the respective cylinder (Z1 to Z4), a crankshaft angle sensor ( 22 ) whose measurement signal is representative of a crankshaft angle of a crankshaft ( 21 ), in which - within a given operating range of the internal combustion engine upon satisfaction of at least one predetermined condition, a cylinder-specific diagnosis is carried out with respect to pollutant emissions, wherein during the execution of the cylinder-specific diagnosis, the diagnosis is actively carried out only during a respective plateau phase of a control signal of a lambda control. The method of claim 1, wherein a duration (T9, T11) of the respective plateau phase of the control signal of the lambda control during the diagnosis is extended so that it is longer than a working cycle or a predetermined multiple of working games. Method according to one of the preceding claims, in which the duration (T9, T11) of the plateau phase of the control signal of the lambda control is set during the diagnosis as a function of a maximum oxygen storage capacity of an exhaust gas catalytic converter. Method according to one of the preceding claims, wherein the diagnosis comprises a run-trouble-based cylinder-specific diagnosis with respect to pollutant emissions. Method according to one of the preceding claims, in which the diagnosis comprises a cylinder-specific lambda control. Device for operating an internal combustion engine having a plurality of cylinders (Z1 to Z4), to which respective injection valves ( 34 ) are assigned for metering fuel, and an exhaust gas probe ( 41 ) with a jump probe characteristic in an exhaust tract ( 40 is arranged and whose measurement signal is characteristic of the air / fuel ratio in the respective cylinder (Z1 to Z4), and a crankshaft angle sensor ( 22 ) whose measurement signal is representative of a crankshaft angle of a crankshaft ( 21 ), wherein the device is designed such that - within a predetermined operating range of the internal combustion engine upon satisfaction of at least one predetermined condition a cylinder-specific diagnosis is carried out with respect pollutant emissions, wherein during the execution of the cylinder-specific diagnosis, the diagnosis active only during a respective plateau phase of a control signal a lambda control is performed.

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