JP2006161812A - Operation method for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve an operation method for an internal combustion engine for determining or measuring gas pressure (gas pressure per cylinder) acting in a combustion chamber of a cylinder to set a mixture existent in the combustion chamber as accurately as possible. <P>SOLUTION: In this operation method for the internal combustion engine, gas pressure p (gas pressure per cylinder) acting in the combustion chamber of the cylinder is determined or measured. It is proposed to determine 48 gas mass m<SB>L</SB>per cylinder based on gas pressure p per cylinder. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention firstly relates to an operating method of an internal combustion engine in which gas pressures (gas pressures for each cylinder) acting in a combustion chamber of a cylinder are determined or measured. The invention also relates to a computer program, an electrical storage medium, an operating / control device for an internal combustion engine and an internal combustion engine.

  A method of the type mentioned at the outset is known from DE 102 40 492. Here, a quantity equalization control and a rotation regularity control using a pressure sensor signal for measuring the gas pressure acting in particular in the combustion chambers of the individual cylinders are disclosed. The background of this measure is that rotational irregularities can occur when there is an error in the amount of fuel delivered.

  By means of quantity equalization control or rotation regularity control, for example, the injection quantity error that occurs during operation of the diesel engine, i.e. the injection quantity error that forms a torque difference and thus irregular engine speed, can be eliminated by the control. The uncomfortable ride comfort in the low rotational speed range known in internal combustion engines can be essentially improved. A pressure sensor for measuring the gas pressure per cylinder is known from DE 19749814.

  In modern internal combustion engines, higher and higher requirements are set for the exhaust gas characteristic values. In addition, newer combustion methods have been devised, such as homogeneous diesel combustion. Controls and / or operations that operate on a cylinder-by-cylinder basis should be used in order to be able to meet their associated requirements.

  It is an object of the present invention to improve a process of the type described at the beginning so that the mixture present in the combustion chamber can be set as accurately as possible.

  This problem is solved in a method of the type described at the outset by determining the gas mass for each cylinder based on the gas pressure for each cylinder. In computer programs, electrical storage media, operating / control devices and internal combustion engines of the type described at the outset, the setting problem is correspondingly solved.

  The method according to the invention makes it possible to provide the individually present gas mass, also called “cylinder filling”, as a variable that can be used for the control and / or operation of the internal combustion engine. However, if the actual gas mass for each cylinder is known, the mixture for each cylinder can be set with high accuracy. This makes it possible to improve the emission characteristics of the internal combustion engine and finally to form a special combustion method by which, for example, the fuel consumption of the internal combustion engine can be reduced.

Advantageous modifications of the invention are described in the dependent claims.
First, in an internal combustion engine having a plurality of cylinders, it is proposed that a first comparison variable is determined from a gas mass for each cylinder and compared with a second comparison variable determined independently of the gas mass for each cylinder. Is done. Such a comparison variable is, for example, an air mass flow rate, and the air mass flow rate is formed by the rotational speed of the internal combustion engine from the gas mass for each cylinder. The comparison performed by the present invention can increase the accuracy in determining the gas mass for each cylinder, or increase the accuracy of the second comparison variable.

  Furthermore, in a variant, it is proposed that the second comparison variable is determined from the air mass sensor signal. Such an air mass sensor makes it possible to provide a very accurate second comparison variable that is present in all normal internal combustion engines and is redundant with respect to the first comparison variable. In this case, the accuracy of the air mass sensor can be further improved by dynamically correcting the signal of the air mass sensor. This belongs to the fact that the accumulator effect of the supply air cooling device and the intake pipe present in some cases is taken into account. It can be seen that the air mass sensor signal can only be used when the existing exhaust gas recirculation is closed in order to form the second comparison variable.

  As a function of the comparison, the model by which the operation or influence variable of the internal combustion engine is determined may be corrected, or the operation or influence variable may be corrected directly. Such an operation or influence variable may be, for example, the modeled gas temperature inside the combustion chamber of the cylinder. This increases the accuracy in the operation or control of the internal combustion engine.

  Such a correction embodiment can be achieved, for example, when a difference between a first comparison variable and a second comparison variable is fed into the PI controller, which is a model for determining an operating or influence variable. It may be to correct (monitor structure) or to directly correct driving or influence variables. Such correction can be easily performed by software.

  Furthermore, when the intake air temperature is measured by the sensor, the gas mass temperature (cylinder temperature) for each cylinder is determined from the measured temperature at least when the intake valve of the cylinder is closed. It is particularly preferred when the temperature per cylinder is used together with the pressure per cylinder to calculate the gas mass. Such a sensor for measuring the intake air temperature already exists in many internal combustion engines, so this does not incur additional costs. With this model, from this temperature it is possible to determine the temperature of the air mass present in the combustion chamber of the cylinder with respect to the time just before the start of compression. Here, the gas mass for each cylinder can be easily calculated by an equation for an ideal gas that is generally known.

  In this case, the accuracy in determining the gas mass for each cylinder is enhanced by taking into account the heat exchange between the gas and the wall of the internal combustion engine in determining the temperature for each cylinder. For example, heat exchange in the intake pipe, between the intake pipe wall and the inflow gas, and between the intake valve and the inflow gas also belongs to this. In order to evaluate these heat transfer, the cylinder head temperature or the cooling water temperature of the internal combustion engine which is also normally known may be used.

  The accuracy in determining the gas mass for each cylinder is further enhanced by taking into account the residual gas present in the combustion chamber of the cylinder in determining the temperature for each cylinder. Such residual gas may be present in the cylinder in the internal exhaust gas recirculation and form a very specific temperature of the gas mass present in the combustion chamber of the cylinder by corresponding mixing with the incoming fresh air. Because there is.

  Furthermore, it is particularly advantageous when the gas mass per cylinder is determined several times during the compression stroke of the cylinder and an average value is formed therefrom. This likewise increases the accuracy in determining the gas mass for each cylinder. However, it should be noted that in this case, the effect of heat exchange between the gas confined in the combustion chamber and the combustion chamber wall increases with increasing compression. This can be taken into account by an appropriate model.

  In this case, the determination of the gas mass is calculated in the following boundary conditions: (a) the combustion chamber is closed after the closing of the injector or injectors, and the intake valve and / or The non-tightness of exhaust valves and / or piston seals was ignored, (b) no fuel injection, and (c) no combustion in the combustion chamber. Sometimes especially easy. These boundary conditions limit the range for the analytical calculation of the gas mass present in the cylinder to the compression stroke between the closing time of one or more intake valves and the start of combustion.

  For example, if the consideration of heat exchange between the gas trapped in the combustion chamber and the combustion chamber wall should be omitted to save computation time, the gas mass per cylinder is approximately equal to the intake valve closing time. It is advantageous when determined only between a crank angle of 50 ° before top dead center. Within this operating range, the pressure is still small, so omission of heat exchange does not significantly affect the results.

  A particularly advantageous variant of the method according to the invention is that the λ value per cylinder is calculated from the gas mass per cylinder, and this calculated λ value is averaged for each cylinder measured by the λ sensor and / or for the entire cylinder. The λ value is compared with the measured λ value. Obviously, in this case, not only the λ value but also other equivalent variables may be used. By such a comparison, the model (monitor structure) for determining the driving or influence variable may be corrected, or the driving or influence variable may be corrected directly. Finally, this can likewise improve the accuracy in the operation or control of the internal combustion engine.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  In FIG. 1, the internal combustion engine has a reference numeral 10 as a whole. Internal combustion engine 10 as a whole includes four cylinders 12a-12d each having a combustion chamber 14a-14d. Combustion air reaches the combustion chambers 14 a-14 d via the intake valves 16 a-16 d, and an intake bend (curved pipe) (not labeled) is connected to the intake valves 16 a-16 d, and the intake bend collects in the intake pipe 18. is doing. A throttle valve 20 is disposed in the intake pipe 18, and the throttle valve 20 can set the flow rate of air reaching the combustion chambers 14a-14d.

  From the combustion chambers 14a-14d, the combustion exhaust gas is exhausted into the exhaust bend (not numbered) and finally into the exhaust pipe 24 through the exhaust valves 22a-22d. In the exhaust pipe 24, an exhaust gas aftertreatment device 26, which is a particle filter or an oxidation catalyst, for example, is arranged. The fuel reaches the combustion chambers 14a-14d via the injection nozzles 28a-28d, respectively, and the injection nozzles 28a-28d inject the fuel directly into the respective combustion chambers 14a-14d. The injection nozzles 28 a-28 d are connected to the fuel system 30.

  The operation of the internal combustion engine 10 is operated or controlled by the operation / control device 32. In particular, the throttle valve 20 and the injection nozzles 28a-28d are operated. For this purpose, the operating / control device 32 receives signals from various sensors. The air mass sensor 34 (HFM sensor) for measuring the mass flow rate of the air mass flowing in the intake pipe 18 and the temperature sensor 36 for measuring the temperature of the intake air flowing in the intake pipe 18 belong to these sensors. The other temperature sensor 38 measures the cylinder head temperature of the internal combustion engine 10, and the rotational speed sensor 40 measures the rotational speed of the crankshaft of the internal combustion engine 10 not shown in FIG. Each combustion chamber 14a-14d is further provided with a unique pressure sensor 42a-42d that measures the gas pressure acting in the respective combustion chamber 14a-14d. A λ sensor 44 located in the exhaust pipe 24 determines the λ value, ie the composition of the fuel / air mixture.

  In an embodiment not shown, the throttle valve is not used for output control, and instead a different amount of fuel is injected. This applies in particular to embodiments of internal combustion engines as diesel engines. In a diesel engine, the exhaust gas recirculation rate is indirectly controlled via the fresh air mass. In order to control the exhaust gas recirculation, firstly an exhaust gas recirculation valve is used. For example, in a specific operating mode for regeneration of the NOx catalyst, the exhaust gas recirculation rate can also be increased by being throttled by a throttle valve. Furthermore, the internal combustion engine may include a turbocharger. In this case, a λ sensor would be placed downstream of the turbocharger turbine.

FIG. 2 schematically shows a first operating method of the internal combustion engine 10 of FIG. First, at block 46, the temperature T _ES — i (i = _ad ) of the gas mass present in the combustion chambers 14a-14d is determined for each point in time when the respective intake valves 16a-16d are closed. . For this purpose, the intake temperature t _ans provided from the temperature sensor 36 and the temperature t _mot of the cylinder head of the internal combustion engine 10 are supplied into the block 46 via the temperature sensor 38. In block 46, the temperature T _{ES — i} is calculated by an appropriate model. The model considers heat exchange between the intake air and one intake pipe 18 and the other intake valve 16a-16d, and in some cases also considers the temperature of the residual gas present in the combustion chambers 14a-14d. . In some cases, signals from other sensors may also be taken into account in modeling the temperature T _ES — i (i = _ad ).

Next, the temperature T _{ES — i} is provided in block 48. Block 48 also receives the actual pressure value _p a -p _d from the pressure sensor 42a-42d. Under the assumption that the combustion chambers 14a-14d form a closed system, no fuel is injected and no combustion takes place, at block 48, based on the ideal gas law, the temperature T _{ES — i} and the gas per cylinder From the pressure p _i (i = _ad ), the gas mass m _{L_i} (i = _ad ) confined in each combustion chamber 14a-14d can be calculated.

In this case, this calculation is performed not only when the intake valves 16a-16d of the corresponding combustion chambers 14a-14d are closed, but also fuel is injected into the combustion chambers 14a-14d from the corresponding injection nozzles 28a-28d. Iterates continuously during the compression stroke of each cylinder 12a-12d up to the point in time. The values m _{L — i} for the trapped gas mass obtained in the multiple calculations are averaged for each combustion chamber 14a-14d.

In this case, the temperature used for the calculation to increase accuracy is also adapted, in which the confinement starts with the temperature T _{ES — i} and increases with the compression of the confined gas mass and the increase in pressure. Considering the heat exchange between the gas being gas and the walls of the respective combustion chambers 14a-14d, the actual temperature of each trapped and compressed gas is calculated.

In addition, in a non-illustrated embodiment, a relatively simple model is used, in which increased heat exchange between the trapped gas and the walls forming the boundaries of the combustion chambers 14a-14d. Is not considered. Nevertheless, in order to obtain good results, the calculation of the trapped gas mass m _{L_i} is about 50 ° before the top dead center of the piston of the corresponding cylinder 12a-12d from the closing time of the corresponding intake valve 16a-16d. Limited to the operating range of each cylinder 12a-12d over the crank angle.

The calculated air mass m _L — i (i = _ad ) is supplied on the one hand in block 50 and on the other hand in block 52. In block 50, the respective difference to the target air mass m _{L_soll} is calculated, and this difference is then used in block 54 for the corresponding correction. In the block 52, the fuel mass m _{K_i} (i = _ad ) injected from the corresponding injection nozzles 28a-28d into the respective combustion chambers 14a-14d is also supplied. The λ value λ _i (i = _ad) for each cylinder can be determined from the fuel mass m _{K_i} and the air mass m _{L_i} in consideration of the known theoretical coefficient. This λ value λ _i for each cylinder can then be compared in comparison block 56 with the λ value λ ₄₄ measured by λ sensor 44.

  FIG. 3 shows another method of operating the internal combustion engine of FIG. In this case, such elements and ranges having the same functions as those already described with respect to FIGS. 1 and 2 have the same reference numerals. These are not described in detail again.

In the method shown in FIG. 3, the gas mass m _{L_i} for each cylinder is averaged in block 58, and the average mass value is obtained from the crankshaft rotation speed n provided from the rotation speed sensor 40 according to the average value. dt is calculated. As will be apparent from the following description, the air mass flow rate dm / dt is the first comparison variable. At the same time, in block 60, the air mass flow rate (dm / dt) ₃₄ is similarly calculated from the signal of the HFM sensor 34 by a physical model such as the intake pipe 18 and the intake bend. This air mass flow rate (dm / dt) ₃₄ is a second comparison variable. In this case, a dynamic correction of the signal of the HFM sensor 34 is also performed at block 60, for example to take into account the accumulator effect of the intake pipe 18. Here, at block 62, a difference between both comparison variables dm / dt and (dm / dt) ₃₄ is formed and this difference is fed into the PI controller 64. This PI controller 64 _corrects the calculation model in block 46 in which the temperature T _{ES — i} is calculated in the sense of the monitor structure.

1 is a schematic system diagram of an internal combustion engine. It is a flowchart of the operating method of the internal combustion engine of FIG. 2 is a flowchart of another operation method of the internal combustion engine of FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12, 12a-12d Cylinder 14, 14a-14d Combustion chamber 16, 16a-16d Intake valve 18 Intake pipe 20 Throttle valve 22a-22d Exhaust valve 24 Exhaust pipe 26 Exhaust gas aftertreatment device 28a-28d Injection nozzle 30 Combustion System 32 Operation / control device 34 Air mass sensor (HFM sensor)
36, 38 Temperature sensor 40 Rotational speed sensor 42a-42d Pressure sensor 44 Lambda sensor 46, 48, 50, 52, 54, 56, 58, 60, 62 Block 64 PI controller dm / dt, (dm / dt) ₃₄ Air Mass flow (comparative variable)
m _{K_i} (i = _ad ) Injection fuel mass m _L , m _{L_i} (i = _ad ) Gas mass (air mass)
m _{L_soll} target air mass p, p _i (i = _ad ) Gas pressure T _ES , T _ES — _i (i = _ad ) Gas mass temperature (operation or influence variable)
t _ans intake air temperature t _mot cylinder head temperature λ, λ ₄₄ , λ _i (i = ad) λ value

Claims (16)

In the operating method of the internal combustion engine (10), wherein the gas pressure (p) (gas pressure for each cylinder) acting in the combustion chamber (14) of the cylinder (12) is determined or measured,
A method for operating an internal combustion engine, characterized in that a gas mass (m _L ) for each cylinder is determined based on a gas pressure (p) for each cylinder (48). In an internal combustion engine (10) having a plurality of cylinders (12), the first comparison variable (dm / dt) is determined from the gas mass per cylinder _{(m L),} and a gas mass per cylinder and _{(m L)} 2. The method of claim 1, wherein is compared (62) with an independently determined second comparison variable ((dm / dt) ₃₄ ). Method according to claim 2, characterized in that the second comparison variable ((dm / dt) ₃₄ ) is determined (60) from the signal of the air mass sensor (34).   Method according to claim 3, characterized in that the signal of the air mass sensor (34) is dynamically corrected (60). As a function of comparison, the model (46) by which the operation or influence variable (T _ES ) of the internal combustion engine (10) is determined is corrected, or the operation or influence variable (T _ES ) is corrected directly. A method according to any of claims 2 to 4, characterized in that The difference (62) between the first comparison variable (dm / dt) and the second comparison variable ((dm / dt) ₃₄ ) is fed into the PI controller (64) and the PI controller (64). the method of claim 5, characterized in that to correct or to correct the model to determine operation or effect variables (T _{ES) (46)} (monitor structure), or operation or effect variables (T _ES) directly . The intake air temperature (t _ans ) is measured by the sensor (36);
At least when the intake valve (16) of the cylinder (12) is closed, the temperature (T _ES ) (temperature for each cylinder) of the gas mass (m _L ) for each cylinder is determined from the measured temperature (t _ans ). (46)
In order to calculate the gas mass per cylinder (m _L ), the temperature per cylinder (T _ES ) is used (48) together with the pressure per cylinder (p);
A method according to any one of claims 1 to 6, characterized in that 8. Method according to claim 7, characterized in that heat exchange between the gas and the wall of the internal combustion engine (10) is taken into account (46) in the determination of the temperature per cylinder ( _TES ). 9. The method as claimed in claim 7, wherein the residual gas present in the combustion chamber (14) of the cylinder (12) is taken into account (46) in the determination of the temperature per cylinder (T _ES ). . 10. The method according to claim 1, wherein the gas mass (m _L ) per cylinder is determined a plurality of times during the compression stroke of the cylinder (12) and an average value is formed therefrom. Method according to claim 10, characterized in that the gas mass (m _L ) per cylinder is determined approximately only between the intake valve closing time and a crank angle of 50 ° before top dead center. A λ value (λ) for each cylinder is calculated from the gas mass (m _L ) for each cylinder, and this calculated λ value (λ) is calculated for each cylinder measured by the λ sensor (44) and / or for the entire cylinder. 12. A method as claimed in any one of the preceding claims, characterized in that it is compared with the averaged [lambda] value.   13. A computer program programmed for use in the method of any of claims 1-12.   13. An electrical storage medium for an operating / control device (32) of an internal combustion engine (10), characterized in that a computer program for use in the method according to any one of claims 1 to 12 is stored therein.   13. An operating / control device (32) for an internal combustion engine (10), characterized in that it is programmed for use in the method of any of the preceding claims.   Internal combustion engine (10), in particular for a motor vehicle, having an operating / control device (32) programmed for use in the method according to any of the preceding claims.

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