EP1216352A1

EP1216352A1 - Method for controlling an internal combustion engine

Info

Publication number: EP1216352A1
Application number: EP00945597A
Authority: EP
Inventors: Johann Graf; Michael Henn; Gerhard Schopp
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1999-09-30
Filing date: 2000-06-07
Publication date: 2002-06-26
Anticipated expiration: 2020-06-07
Also published as: US20020121268A1; WO2001023733A1; DE50010987D1; EP1216352B1; US6619262B2; DE19947037C1

Abstract

An internal combustion engine having multiple cylinders to which are associated at least one fuel injection valve and at least one regulating member to regulate the air mass which is supplied to the cylinders, whereby at least one sensor for the detection of a parameter characteristic of the air-fuel ratio in the individual cylinders and at least one sensor for the detection of a parameter characteristic of the torque generated in the individual cylinders or for the detection of a parameter characteristic of the differences in torque generated in the individual cylinders, are provided. The inventive method is according to the following steps: air-fuel ratio for the individual cylinders is determined; the control of at least one fuel injection valve of the individual cylinders is adjusted according to the detected air-fuel ratio and according to the desired parameter of said air-fuel ratio. The parameter which characterises the torque or the differences in torque is determined for the individual cylinders and the control of at least one regulating member which regulates the air mass in the individual cylinders is adjusted according to the torque-characteristic value detected or according to the difference in torque-characteristic parameter and indeed, according to an adjustment in torque generated by the individual cylinders.

Description

description

Method for controlling an internal combustion engine

The invention relates to a method for controlling an internal combustion engine, in particular an internal combustion engine with quantity control, that is to say an internal combustion engine operating on the Otto principle.

In a known method for controlling an internal combustion engine (DE 38 39 611 AI), the air ratio is determined individually for each cylinder using a lambda probe. Depending on the air ratio determined for the respective cylinder, a correction signal for correcting the actuation of a fuel injection valve is determined, namely in the sense of an approximation of all air ratios m in the respective cylinders of the internal combustion engine to the value λ = 1. As an alternative to this, it is known from DE 38 39 611 AI to determine a correction signal for the control of an actuator of a throttle element of the internal combustion engine depending on the respective cylinder-specific air ratio. The disadvantage of both alternatives of the known method is, however, that although the air / fuel ratio in the individual cylinders is approximated to one another, the torques generated in the individual cylinders can vary, which is determined by a driver of a vehicle Internal combustion engine is arranged, is perceived as a non-uniformly running internal combustion engine or as a jerk.

In another known method (WO 90/07051), the torque contributions of the individual cylinders of the internal combustion engine are equalized by monitoring the power output by the respective cylinders and a cylinder-specific correction of the fuel mass depending on the respective power in the cylinder. Although this method brings about an equalization of the torque contributions of the individual cylinders, this method can lead to deviations The air ratio in individual cylinders leads to a predetermined setpoint for the air ratio, which can lead to damage to a three-way catalytic converter arranged in an exhaust tract of the internal combustion engine.

The object of the invention is to provide a method which ensures low-emission and at the same time comfortable control of an internal combustion engine.

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

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

FIG. 1 shows an internal combustion engine with a control device,

FIG. 2 shows a flow chart for cylinder equalization, FIG. 3 shows a flow chart of a main control function in the control device 6,

Figure 4 shows a further flow diagram for cylinder equalization.

Elements of the same construction and function are provided with the same reference symbols in all figures.

An internal combustion engine (FIG. 1) comprises an intake tract, to which a throttle valve 10 and at least one injection valve 15 are assigned, and an engine block 2, which has a cylinder 20 and a crankshaft 23. A piston 21 and a connecting rod 22 are assigned to the cylinder 20. The connecting rod 22 is connected to the piston 21 and the crankshaft 23. The injection valve 15 is provided either for injecting fuel into a plurality of cylinders of the internal combustion engine or only for injecting fuel into one cylinder of the internal combustion engine in each case. In the latter case an injection valve 15 is assigned to each cylinder 20 of the internal combustion engine. The injection valve 15 can alternatively also be provided in a cylinder head 3 and be arranged such that the fuel is metered directly into the combustion chamber of the cylinder 20. Alternatively, the injection valve 15 can also be arranged towards a mixing chamber of a mixture injector, which blows the air / fuel mixture from the mixing chamber directly into the cylinder 20.

A valve train is also arranged in the cylinder head 3, with at least one inlet valve 30 and one outlet valve 31. The valve train comprises at least one camshaft, not shown, with a transmission device which transmits the cam stroke to the inlet valve 30 or the outlet valve 31. Devices for adjusting the valve lift times and / or the valve lift curve are preferably also provided. Such a device for adjusting the valve stroke curve of a gas exchange valve is known from DE 42 44 550 AI. This device is preferably used for throttle-free load control of gasoline engines. The device has two opposing camshafts, which act on the gas exchange valve via a rocker arm. One of the camshafts determines the open function and the other camshaft the closing function of the gas exchange valve. The valve stroke profile of the gas exchange valve, i.e. the stroke and the opening duration, can be changed over a wide range by a relative rotation of the two camshafts relative to one another by means of a four-wheel coupling gear, a corresponding actuator being provided for adjusting the relative rotation.

Alternatively, an electromechanical actuator can also be provided which controls the course of the valve lift of the intake or exhaust valve 30, 31. Such an electromechanical actuator is known for example from DE 297 12 502 U1.

The actuator comprises a spring-mass oscillator with an armature. The actuator also includes two electromagnets. The arrival ker acts on the gas exchange valves, that is, the inlet valve 30 or the outlet valve 31. If an electromechanical actuator is provided for controlling the gas exchange valves, there is no camshaft.

A spark plug 34 is also introduced into the cylinder head 3. The internal combustion engine is shown in FIG. 1 with a cylinder 20. However, it includes other cylinders Z2, Z3, Z4. The cylinders Z2 to Z4 are preferably identical to the cylinder 20. Furthermore, they are each assigned at least one outlet valve 31 and one inlet valve 30.

An exhaust tract 4 with a catalyst 40 and an oxygen probe 41 is assigned to the internal combustion engine. A

Control device 6 is provided, to which sensors are assigned, which record different measured variables and each determine the measured value of the measured variable. The control device 6 determines one or more control signals depending on at least one measured variable, each of which controls an actuator. The

Sensors are a pedal position sensor 71, which detects a pedal position of the accelerator pedal 7, a throttle valve position sensor 11, which detects an opening degree of the throttle valve 10, an air mass meter 12, which detects an air mass flow MAF, and / or an intake manifold pressure sensor 13, which detects an intake manifold pressure in the intake tract 1 , a first temperature sensor 14, which detects an intake air temperature, a speed sensor 24, which detects a rotational speed N of the crankshaft 23, a second temperature sensor 25, which detects a coolant temperature TCO, a combustion chamber pressure sensor 26 which detects the pressure P_BR in the interior of the cylinder 20, that is to say in the combustion chamber, and the oxygen probe 41, which detects the residual oxygen content of the exhaust gas in the exhaust tract 4 and which assigns the measured value of the air ratio λ to it. The air ratio λ is the ratio of the air mass supplied to the cylinder 20 to the theoretical air requirement for stoichiometric ratios for the amount of fuel injected. The air supply Ratio is therefore a variable that characterizes the air / fuel ratio.

Furthermore, a torque sensor 28 is preferably provided, which detects the torque that is generated in the individual cylinders 20, Z2-Z4 on the crankshaft 23. Depending on the embodiment of the invention, any subset of the sensors mentioned or additional sensors can be present.

The actuators each include an actuator and an actuator. The actuator is an electromotive drive, an electromagnetic drive or another drive known to those skilled in the art. The actuators are designed as a throttle valve 10, as an injection valve 15, as a spark plug 34 or as a device for adjusting the valve lift of the intake or exhaust valves 30, 31 or as electromechanical actuators for controlling the valve lift of the intake and exhaust valves 30, 31. The actuators are referred to below with the respectively associated actuator.

If one or more devices for adjusting the valve stroke of the intake or exhaust valves 30, 31 or electromechanical actuators are provided for adjusting the air mass in the cylinders 20, Z2-Z4, then the throttle valve 10 may be dispensed with. The control device 6 is preferably designed as an electronic engine control. However, it can also comprise several control devices which are connected to one another in an electrically conductive manner, for. B. via a bus system.

FIG. 2 shows a flowchart of a method for controlling the internal combustion engine, which effects an equalization of the cylinders 20, Z2 to Z4. The program is stored in the control device 6 and is processed there. The program can be executed either at predetermined time intervals during the operation of the internal combustion engine or in predetermined operating states of the internal combustion engine become. Such an operating state can be, for example, a steady-state partial load operation or an idling operation, or it can be characterized in that the coolant temperature TCO exceeds a predetermined threshold value.

The program is started in a step S1. In a step S2, the air ratio λ is determined individually for the cylinder, which is represented by the λ indicated by i. The air ratio λ that can be assigned to each cylinder 20, Z2 to Z4 is calculated at least once, which is then a measure of the respective air / fuel ratio in the respective cylinder 20, Z2 to Z4. Alternatively, the cylinder-specific determination of the air ratio λ _ for each cylinder can be carried out averaged over several work cycles.

In a step S3, a first correction value Kl _x for each of the cylinders 20, Z2 to Z4 is determined as a function of the air ratio λ _x assigned to the respective cylinder and a target value λ _{sp of} the air ratio. The target value λ _sp can be equal to one, for example, in order to ensure a stoichiometric air / fuel mixture in the cylinders 20, Z2 to Z4. The first correction value Kl _x is used in the program shown in FIG. 3 for the general control of the internal combustion engine and is described in more detail below.

In a step S4, the program can remain in a waiting state for a predetermined period of time or alternatively can go directly to step S5.

In step S5, the torque TQ ^ for each cylinder 20, Z2 to Z4. determined, which is generated by him. For this purpose, either the measurement signal of the torque sensor 28 or the measurement signal of the combustion chamber pressure sensor 26 is evaluated or, for example, the measurement signal of the speed sensor 24. Average values of the respective cylinders can also be torque TQ _X can be determined over several work cycles of the internal combustion engine.

In a step S6, a second correction value K2_ is calculated individually for each cylinder 20, Z2 to Z4 depending on the torque TQi assigned to each cylinder Z2 to Z4, 20 and an average value TQ_MV of the torques calculated by averaging all torques TQ _X. The second correction value K2 ^ _. is used in the general program for controlling the internal combustion engine described in FIG. The program is then ended in a step S7.

In a step S10 (FIG. 3), a main program for controlling the internal combustion engine is started. In a step S11, a setpoint TQI_SP of the torque to be generated by the internal combustion engine is calculated as a function of the rotational speed N, the accelerator pedal value PV and further operating variables of the internal combustion engine, such as the coolant temperature TCO, and further torque contributions, such as from an electronic transmission control or traction control system ,

In a step S12, a fuel injection period T _K sτι for the one or more injection valves 15 is calculated individually for each cylinder. For this purpose, the fuel injection time period T _K sτ_ is calculated for each cylinder 20, Z2 to Z4 as a function of the setpoint value of the torque, the respectively assigned first correction value Kl_ and, if appropriate, further variables. Due to the dependence of the fuel injection time period T _K sτ_ on the correction value Klj assigned to each of the cylinders 20, Z2 to Z4. it is ensured that the air / fuel ratio in all cylinders is within narrow limits of the specified target value of the air / fuel ratio. As a result, different flow rates of the fuel in the injection valves 15 caused by manufacturing tolerances can be compensated for. In a step Ξ13, a valve lift period T _VH _ is calculated for each individual cylinder 20, Z2 to Z4 as a function of the setpoint TQI_SP of the torque, the second correction value K2 _X assigned to the respective cylinder 20, Z2 to Z4 and possibly further variables. Dependent on the assigned to the respective cylinder Ventilhubzeitdauer T _ _VH are then, depending on the embodiment of the internal combustion engine, the Dros ^¬ selklappe 10 or electromechanical actuators or the input device or the means for adjusting the Vent lhub- times driven.

Alternatively, in step S13, a maximum valve lift or a valve lift profile can also be determined as a control variable for controlling the devices for adjusting the valve lift profile.

The dependency of the valve lift period T _VHI on the second correction value K2i assigned to the respective cylinder ensures that the torques generated in the respective cylinders are the same.

Steps S12 and S13 thus advantageously ensure that both the air / fuel ratio m in each cylinder 20, Z2 to Z4 of the internal combustion engine corresponds to the predetermined target value and that the torque generated in the respective cylinders is the same. On the one hand, this ensures efficient and gentle operation of the catalytic converter 14 with a corresponding emission reduction, and on the other hand ensures a high level of driving comfort for a vehicle in which the internal combustion engine is arranged. In a step S14, the program is ended. The program according to FIG. 3 is preferably called up at predetermined time intervals or as a function of the rotational speed N.

FIG. 4 shows a further method for equating the cylinders. Steps S1 to S4 are identical to the speaking steps in FIG. 2. In a step S17 following step S4, the speed N _x assigned to the respective cylinder is determined individually for each cylinder 20, Z2 to Z4. For example, the speed is determined during the expansion stroke of the respective cylinder or in a subsequent stroke or segment. A segment is determined by the time interval between the top dead centers of two cylinders that follow one another in the firing order.

In step S18, an uneven running value LUi is determined for each cylinder 20, Z2 to Z4 as a function of the rotational speed N _x determined for the respective cylinder 17. A dependency on the third power of the respective speed N _{x has} proven to be particularly advantageous. The

Uneven running is a measure of differences between the torques generated by the cylinders. Alternatively, the rough running values LU _{X can} also be determined as a function of a change in the rotational speed N _{x associated with} the respective cylinder.

In a step S19, the second correction value K2_ is individual for each cylinder depending on the respective rough running value LU. determined. This is done in the sense of an adjustment of the torques generated by the individual cylinders. In the case of an existing torque sensor 28, a deviation of the individual torque from the torque averaged over all cylinders can also be calculated individually for each cylinder and then the second correction value K2 _α can be calculated depending on this deviation.

A corresponding procedure is also advantageous if a combustion chamber pressure sensor 26 is present. The program is then ended in a step S20.

It is particularly advantageous if the actuator for adjusting the air mass to be supplied to the cylinders 20, Z2 to Z4 Intake valves 30 are. This ensures that the respective air mass in the cylinders can be set with a very high temporal resolution and an extremely short dead time.

Claims

claims

1. A method for controlling an internal combustion engine with several ^¬ ren cylinders (20, Z2, Z3, Z4), which at least one fuel consum- associated femspritzventil (15) and at least one actuator for adjusting the cylinders supplied air mass, at least one sensor for Detecting a variable characterizing the air / fuel ratio in the individual cylinders (20, Z2, Z3, Z4) and at least one sensor for detecting a torque that is generated in the individual cylinders (20, Z2, Z3, Z4) , characterizing sizes are provided, with the following steps:

- The size that characterizes the air / fuel ratio is determined individually, - The actuation of the at least one fuel injection valve (15) is corrected individually for the cylinder, depending on the size that is individually determined for the cylinder, which characterizes the air / fuel ratio, and one Setpoint value of the size that characterizes the air / fuel ratio,

the size characterizing the torque is determined for each cylinder,

- The activation of the at least one actuator for adjusting the air mass is corrected individually for the cylinder depending on the detected value of the quantity characterizing the torque and in the sense of an approximation of the torques generated by the individual cylinders (20, Z2, Z3, Z4).

2. The method according to claim 1, characterized in that the size characterizing the torque is the torque

3. The method according to claim 1, characterized in that the size characterizing the torque is the combustion chamber pressure (P BR).

4. A method for controlling an internal combustion engine with a plurality of cylinders, to which at least one fuel injection valve (15) and at least one actuator for adjusting the air mass to be supplied to the cylinders (20, Z2, Z3, Z4) are assigned, at least one sensor for detecting a

Air / fuel behavior in the individual cylinders characterizing variable and at least one sensor for detecting a variable, which is characteristic of differences between the torques generated in the cylinders (20, Z2, Z3, Z4), are provided, with the following steps:

the size characterizing the air / fuel ratio is determined individually for the cylinder,

- The actuation of the at least one fuel injection valve (15) is corrected individually for the cylinder depending on the size detected individually for the cylinder, which

/ Characterized fuel ratio, and a target value of the size that characterizes the air / fuel ratio,

the size, which is characteristic of differences between the torques generated in the cylinders (20, Z2, Z3, Z4), is determined for each cylinder,

- The activation of the at least one actuator for adjusting the air mass is corrected individually for the cylinder depending on the size, which is characteristic of differences between the torques generated in the cylinders (20, Z2, Z3, Z4), namely in the sense of an adjustment of the Torques generated by the individual cylinders (20, Z2, Z3, Z4).

5. The method according to claim 4, characterized in that the size, which is characteristic of differences between the torques generated in the cylinders (20, Z2, Z3, Z4) is derived from the speed (N) of the crankshaft (23).

6. The method according to claim 4, characterized in that the size, which is characteristic of differences between the torques generated in the cylinders (20, Z2, Z3, Z4) is derived from a measurement signal of a combustion chamber pressure sensor (26).

7. The method according to any one of the preceding claims, characterized in that the actuator for adjusting the air mass to be supplied to the cylinders (20, Z2, Z3, Z4) is a gas exchange valve.