WO2014090544A1

WO2014090544A1 - Method for operating an internal combustion engine

Info

Publication number: WO2014090544A1
Application number: PCT/EP2013/074444
Authority: WO
Inventors: Nils Lindenkamp; Henrik HOFFMEYER; Dirk Hagelstein
Original assignee: Volkswagen Aktiengesellschaft
Priority date: 2012-12-13
Filing date: 2013-11-22
Publication date: 2014-06-19
Also published as: DE102012024318A1

Abstract

A method for operating an internal combustion engine is disclosed. The internal combustion engine has at least one combustion chamber, an intake pipe, a compressor for generating a charge with a charge density in the intake pipe and a device for modifying a volumetric efficiency of the charge from the intake pipe into the at least one combustion chamber. In the method, a part of the charge is transferred from the intake pipe into the at least one combustion chamber with a volumetric efficiency which is adjusted as a function of the charge density. The volumetric efficiency is determined and adjusted on the basis of the air pressure prevailing in an environment of the internal combustion engine.

Description

Description Method for operating an internal combustion engine

The invention relates to a method for operating an internal combustion engine having the features according to the preamble of claim 1.

Currently widely used for internal combustion engines, in particular gasoline engines are limited in their thermodynamic efficiency due to the necessary throttling of the quantitative load control and the reduced compression ratio to avoid engine knock. A common approach for Entschrosselung in partial load operation and / or to reduce the compression end temperature, the so-called Miller method and / or Atkinson method - in this illustration simplifies all referred to as Miller method -. The air consumption and the effective compression are reduced by the intake into the combustion chamber is already closed at an early point of time in relation to top dead center ("early intake closes", FES) or by closing the intake into the combustion chamber at a late time with respect to top dead center ("late intake closes ", SES). One operated by a Miller process

Internal combustion engine may be designed or constructed so that in comparison to a conventionally operated internal combustion engine, an increased geometric

Compression ratio is present.

In order to be able to compensate for the filling loss occurring in a Miller process without loss of torque, the intake manifold pressure and thus the compression capacity must be significantly increased. In order to be able to represent the increased compression capacity, preference is given to using either an exhaust gas turbocharger (ATL) with variable turbine geometry or a multi-stage, for example two-stage charging, for example by means of a waste gate ATL in combination with a mechanically driven compressor. In general, the size and thermodynamics of an ATL compressor is designed so that all compressor operating points at all times, in particular the full load curve, within the so-called surge limit, plug limit and speed limit, which limit the displayable characteristic diagram in the pressure ratio graph as a function of the reduced mass flow, are located. Even with decreasing air pressure, for example, with increasing geodesic Height position of the vehicle above sea level (sea level), the same

To achieve full load torque, the compressor must provide a higher pressure ratio. In practice, this is achieved by a significant increase in the ATL speed, but it must always be ensured even under these conditions that all engine operating points are safely within the representable characteristic map of the compressor. In addition, in addition to the altitude reserve in general - if no speed sensor is installed on the ATL - still a speed reserve for on-board diagnostic (OBD) functions must be kept, for example, for leakage detection. As OBD speed reserve, in practice, approximately 5 to 10% of the maximum ATL speed is kept available.

These facts disadvantageously lead to the situation that the ATL of a motor with standard control times are therefore always designed in size and thermodynamics so that the ATL can be operated safely under all boundary conditions, such as heat or altitude. As a consequence, the ATL tends to be too large for standard conditions (20 C, 0m height). This in turn has the consequence that on the one hand, the torque at low speeds (low-end torque) and the response of the ATLs is not optimal or the potential is not fully utilized. This problem is exacerbated significantly at an increased boost pressure, as it is needed in a Miller process.

Document DE 102 34 103 A1 describes a method for controlling an intake valve of an internal combustion engine with an air intake pipe. A closing time of the

Inlet valve is controlled in response to a gas pressure wave, which is caused for example by air pressure oscillations in the air intake pipe. In this case, the closing time in a working cycle relative to the crankshaft angle may be different from the closing time in the previous working cycle.

Object of the present invention is to operate an internal combustion engine with a compressor within the displayable map.

This object is achieved by a method for operating a

Internal combustion engine solved with the features of claim 1. Advantageous developments of the invention are characterized in the dependent claims. In the method according to the invention for operating an internal combustion engine having at least one combustion chamber, a suction tube, a compressor for generating a charge with a charge density in the intake manifold and a device for varying a delivery of the charge from the intake manifold into the at least one combustion chamber, becomes a part of the charge transferred from the intake manifold in the at least one combustion chamber with a degree of delivery, the degree of delivery is set in function of the charge density. The degree of delivery is inventively determined and adjusted depending on the pressure prevailing in an environment of the engine air pressure.

The internal combustion engine is preferably a piston engine, in particular with several, for example three, four or six pistons. The combustion chamber is preferably a cylinder combustion chamber. The compressor may in particular be the compressor of an exhaust gas turbocharger or an electrically driven compressor (e-booster). The apparatus for varying the delivery rate is in a preferred embodiment part of a device for varying the inlet and / or outlet times and / or inlet and / or outlet profiles of the inlet and / or

Exhaust devices of the combustion chamber, for example part of a variable valve train. The environment in particular contains one or is a part of space, from which air passes through the compressor in the suction pipe.

Advantageously, in the method according to the invention, the change or deviation from a standard value of the air pressure prevailing in the surroundings of the internal combustion engine, which inter alia depends on the geodetic height and / or the

Weather condition depends, be responded by an adequate adjustment of the delivery, in particular a compensatory or compensatory attitude. As a result, the operating point or operating point of the compressor does not shift in the map. This fact can be advantageously exploited in the design of compressors: It is no longer necessary when using the method according to the invention, a

Reserve air / reserve reserve, a sufficiently wide distance of the operating points under standard conditions of the boundaries of the map to plan.

It can further in the inventive method for operating a

Internal combustion engine the degree of delivery depending on in an environment of the

Internal combustion engine determined temperature determined, in particular measured, and adjusted. The temperature may in particular be a parameter which influences the pressure to be expected at a certain geodetic altitude above sea level. In a particularly preferred embodiment, the method according to the invention is carried out or used in a spark-ignited internal combustion engine. In other words, the internal combustion engine is preferably a spark-ignited internal combustion engine, for example an Otto engine. It is furthermore particularly preferred that in the method according to the invention the internal combustion engine is operated with a compression ratio of the charge in the combustion chamber which is smaller than the maximum geometric compression ratio of the combustion chamber. In other words, the internal combustion engine is operated in a Miller process. A miller degree is a measure of the size of the reduction of the effective compaction.

In a group of embodiments of the method according to the invention is the

Compression ratio of the charge in the combustion chamber by means of a variation of the

State transition timing, in particular the opening time or the

Closing time, at least one valve changed to the inlet of charge into the combustion chamber. Furthermore, for this purpose, a state transition time, in particular an opening time or a closing time, or

State transition interval, in particular the course of an opening operation or a closing operation, at least one valve to the outlet of charge in the combustion chamber can be varied. Specifically, this variation can be done by means of a variable valve train.

In the method according to the invention can be found after finding the reduction of

Ambient air pressure, the compression ratio of the charge in the combustion chamber are increased and / or after detecting the increase in the ambient air pressure the

Compression ratio of the charge in the combustion chamber can be reduced. In this way, the changed air density in the intake manifold can be compensated by the fact that the geometric

Compression in the combustion chamber is changed counteracting.

Alternatively, after determining the reduction in temperature, the effective

Compression ratio can be reduced and / or increased after determining the increase in the temperature, the effective compression ratio. In this way, the existing at a different temperature changed air density in the intake manifold can be compensated by the geometric compression in the combustion chamber is changed counteracting.

In a group of embodiments of the method according to the invention, first a pressure limit, in particular a lower pressure limit, in the environment of

Internal combustion engine prevailing air pressure determined. The further steps of the

inventive method are performed exactly when the measured Air pressure is beyond the pressure limit, in particular, when the pressure lower limit is reached. Alternatively, in a group of embodiments of the

inventive method first a pressure upper limit for the compressor in

Dependence of the prevailing in the environment of the internal combustion engine air pressure determined. The further steps of the method according to the invention are performed precisely when a pressure to be generated by the compressor is beyond the pressure limit, in particular when the pressure upper limit is exceeded. In this way, a parameter range for the application of the method according to the invention is advantageously determined. If the pressure outside the defined parameter range, in particular another, different from the inventive method for operating a

Internal combustion engine to be performed.

In particularly preferred embodiments of the method according to the invention, the compressor is operated with substantially unchanged parameters while maintaining the power output and changing the air pressure, so that the degree of delivery is changed (when the degree of delivery changes due to a variation of the air pressure). In other words, the use of the method according to the invention causes the compressor with its used parameters, specifically at the same point in the map, the same compressor operating point, can be operated, in particular not beyond the limits of the displayable map. The changed degree of delivery is then at least partially compensated exclusively in accordance with the invention.

In concrete embodiments of the method according to the invention, the air pressure prevailing in an environment of the internal combustion engine can be measured with a pressure sensor. Furthermore, or alternatively, in an environment of the internal combustion engine

prevailing temperature can be measured with a temperature sensor. In other words, a direct measurement of the size can take place in each case. In this way, the actual values required for the method according to the invention can be obtained quickly and directly.

Alternatively to the pressure, the density of the air present in the surroundings of the internal combustion engine can also be measured. A calculating approach involves determining the pressure as a function of the detected geodetic height of the internal combustion engine

Normal zero, for example by means of altitude data, the position of the

Internal combustion engine with the help of a navigation system are available. In a further development, the temperature can be included in the calculation rule as an additional parameter. In the context of the method according to the invention is also an internal combustion engine with a control unit with a computer. The computer of the control unit of the internal combustion engine according to the invention has a memory. In the memory of the computer of the control unit according to the invention a program is stored, which has at least one subsection, in the execution of the internal combustion engine is operated with a method with features or feature combinations according to this diagram.

The internal combustion engine may in particular be a self-igniting or a spark-ignition internal combustion engine (preferred), for example a diesel engine or a gasoline engine (preferred). Particularly preferably, the internal combustion engine is suitable for use in a railless land vehicle, in particular a wheeled vehicle, for example a passenger car or a truck.

Further advantages and advantageous embodiments and developments of the invention will be described with reference to the following description with reference to the figures. It shows in detail:

Figure 1 is a schematic flow diagram of a preferred embodiment of the method according to the invention, and

Figure 2 is a schematic flow diagram of a filling control.

Before the sequence of the preferred embodiment of the method according to the invention is described in more detail with reference to FIG. 1, it will be explained that the method according to the invention is preferably used in a high-compression gasoline engine with valve control times according to a Miller method. In order to prevent engine knocking at a high geometric engine compression ratio, the delivery rate or the air outlay over the Miller control times can be significantly reduced at high engine loads. In order to maintain the efficiency, the reduction in the delivery rate is compensated by increasing the intake manifold pressure, in particular by means of a compressor, for example a turbocharger. The degree of delivery λ | and the intake manifold pressure p _SGR im

Essentially in an inversely proportional relationship:

psgr According to the invention, this relationship is used to be able to comply with the speed limit of the compressor, in particular an exhaust gas turbocharger, even when deviating from a standard air pressure prevailing air pressure, for example, in a certain geodetic height. The air consumption will be so far increased with decreasing air pressure, for example, with increasing height by adjusting the valve train, so changing the valve timing that decreases by reducing the miller wheel of the boost pressure demand and all engine operating points are within the limits of the compressor map.

Referring to Figure 1, in the preferred embodiment of the

According to the method of the invention, in a step 10, a gasoline engine having a plurality, for example three, four or six cylinders as combustion chambers, a suction pipe and at least one compressor, which is part of an exhaust gas turbocharger, is provided. The compressor of the

Exhaust gas turbocharger serves to generate a charge with a charge density in the intake manifold. The gasoline engine has as a device for changing the degree of delivery of the charge from the intake manifold into the cylinders, the combustion chambers, a variable valve train for moving the intake and exhaust valves of the cylinder. In step 12, the gasoline engine with a

Operated compression ratio of the charge in at least one cylinder, which is smaller than the maximum geometric compression ratio of the cylinder. In other words, the gasoline engine is operated in a Miller combustion process. The compression ratio in

Cylinder is then dependent on the miller and less than the geometrically predetermined maximum compression ratio of the cylinder. The effective

Compression ratio, in particular the compression ratio of the charge in the combustion chamber can be changed by means of a variation of the closing time of at least one valve for the introduction of charge into the combustion chamber. In step 14, in an environment of the

Internal combustion engine prevailing air pressure with a pressure sensor and the prevailing in an environment of the internal combustion engine temperature measured with a temperature sensor.

Starting from the concrete technical data of the compressor, in step 16 a pressure upper limit for the compressor in dependence on in the environment of

Internal combustion engine prevailing air pressure determined. If, at a load request, the pressure to be generated by the compressor is beyond the pressure upper limit, then

According to the invention, in step 18, a part of the charge is transferred from the intake manifold into at least one cylinder with a reduced delivery rate. The reduced delivery rate is specifically influenced or controlled by the timing of the intake valves and / or exhaust valves. In this case, the reduced degree of delivery is determined and adjusted as a function of the charge density, wherein the charge density depending on the in an environment of the internal combustion engine, from which air enters the intake manifold via the compressor, the prevailing atmospheric pressure and the temperature prevailing in the surroundings of the internal combustion engine. Quantitatively, the degree of delivery - that is, the control times of the Miller process - changed so that at constant power output despite standard conditions deviating air pressure and different temperature of the compressor with substantially unchanged parameters, ie at the same operating point in the compressor map, operated.

This means, in particular, that at a measured ambient air pressure that is less than the standard air pressure, the compression ratio of the charge in the cylinder is increased and that at a measured ambient air pressure that is higher than the standard air pressure, the compression ratio of the charge in the cylinder is reduced. In particular, it also means that at a measured temperature that is less than the standard temperature or that causes an air pressure higher than the standard air pressure, the compression ratio of the charge in the cylinder is decreased and at a measured temperature that is higher than the standard temperature or the air pressure is lower than the standard air pressure, the compression ratio of the charge in the combustion chamber is increased.

At this point it is not unmentioned that due to the reduction of the Millergrades the knock sensitivity of a high-compression gasoline engine can increase. A possibly necessary delay of the ignition angle and the associated delay of the center of gravity of the combustion can lead to a moderate deterioration of the ignition

Fuel consumption lead. Furthermore, the exhaust gas temperature may increase due to the lower miller degree and the later center of gravity of the combustion. If the permissible exhaust gas temperature for the downstream of the exhaust valve component, for example turbine housing, turbine wheel, catalyst, possibly integrated exhaust manifold, is exceeded in the sequence, the mixture should be greased in the combustion chamber for component protection with fuel. This in turn can lead to a moderate deterioration of the

Fuel consumption lead. To minimize the Anfetten s for component protection offers the integration of a speed sensor in the exhaust gas turbocharger. Thus, when setting the maximum speed of the exhaust gas turbocharger always exactly the minimum or therm odynamically optimal air consumption can be adjusted. With additional elimination of the OBD speed reserve, the miller can be further increased and thus the enrichment further lowered.

By means of the method according to the invention, it is also possible in a high-density Miller process by adapting the timing (adjustment to more air effort) of the valve train to comply with the limits of the compressor map even in heat and altitude to be able to. Therefore, the compressor, in particular the exhaust gas turbocharger, in a high-density Miller process for standard conditions (20 C, 0m height) can be optimally designed.

FIG. 2 is a schematic representation of the concrete procedure for the application of a control unit of an internal combustion engine for carrying out a preferred embodiment of the method according to the invention. The absolute speed limit of the exhaust gas turbocharger is specified by the production. By means of this speed _limit , the maximum possible pressure ratio n _max above the reduced compressor _{mass flow} rh _redy can be derived from the compressor _map . The reduced compressor mass flow rh _red is defined as

where rh _{v is} the compressor _{mass flow} , 7 ^' , a measured temperature, T _liref a

Reference temperature (standard temperature), p ₁ denotes a measured pressure and p _{1> re} a reference pressure (standard pressure). The maximum possible pressure ratio

TTmax = m _{red v} ) is stored as a characteristic curve in the charge control in the engine control unit.

Is the control unit, for example, via the accelerator pedal of the vehicle, a

Moment desired M _so n specified, it implies a desired air mass flow rh _v , which is calculated in the control unit. With an ambient pressure sensor pu and an outdoor temperature sensor Tu, pressure pi and temperature Ti before compressor entry will be determined via a model. Starting from the values Ti, pi and rh _v , the reduced compressor mass flow rh _red is calculated using the formula given above. With rh _red , the current maximum possible pressure ratio is then determined from the characteristic curve _max = {rh _{red v} ).

With TTmax and pi can now be the maximum pressure p ₂ . _max after compressor or in the intake manifold (upper pressure limit) calculate

V2, max - ^π πιαχ * Pl ^■

The value determined from the idea for the required pressure p ₂ after the compressor is compared with the upper pressure limit. Should the determined value for the pressure p ₂ is exceeded, this is limited by the upper pressure limit, so that it is ensured that the maximum speed limit of the exhaust gas turbocharger is not exceeded.

The value for the pressure p ₂ limited in this way is transferred to the actual charge control / charge control. In this module of the control unit, an air expenditure λ is calculated, so that the engine is supplied with the corresponding setpoint air mass rh _LU f _{t> soU} . The air expenditure λ & is then displayed via the valve drive, in particular via a changed control time for the inlet closing or by changing the valve lift.

In summary, it should be emphasized that if the ambient air pressure decreases with increasing altitude and / or the ambient temperature rises significantly, the compressor pressure ratio at the full load must increase to compensate for the lower density before compressor. If the _maximum rotational speed limit for the compressor is exceeded - limited by n _max -, the filling and thus the torque can be represented by an increase in the air consumption, in particular by means of an adjustment of the valve drive. In this way, thereby the speed limit of the exhaust gas turbocharger at any time and among all

Environmental conditions are met.

LIST OF REFERENCE NUMBERS

First Step: Provide an Internal Combustion Engine Second Step: Operate in a Miller Process Third Step: Measure Pressure and Temperature Fourth Step: Determine and Adjust the Degree of Delivery Fifth Step: Transfer the Load

Claims

claims

1 . A method of operating an internal combustion engine having at least one combustion chamber, a suction tube, a compressor for generating a charge with a charge density in the intake manifold and a device for varying a degree of delivery of the charge from the intake manifold in the at least one combustion chamber, in which a part of the charge from Suction tube is transferred to the at least one combustion chamber with a degree of delivery, the degree of delivery is set in function of the charge density,

characterized

the degree of delivery is determined and set as a function of the air pressure prevailing in an environment of the internal combustion engine.

2. A method for operating an internal combustion engine according to claim 1,

characterized

the degree of delivery is determined and set as a function of the temperature prevailing in an environment of the internal combustion engine.

3. A method for operating an internal combustion engine according to claim 1,

characterized

the method is carried out in a spark-ignited internal combustion engine.

4. A method for operating an internal combustion engine according to claim 1,

characterized

that the internal combustion engine is operated with a compression ratio of the charge in the combustion chamber, which is smaller than the maximum geometric compression ratio of the combustion chamber.

5. A method for operating an internal combustion engine according to claim 1,

characterized

that the effective compression ratio is varied by means of a variation of the closing time of at least one valve for the introduction of charge into the combustion chamber.

6. A method for operating an internal combustion engine according to claim 1,

characterized

that upon detection of the reduction in ambient air pressure, the

Compression ratio of the charge in the combustion chamber is increased and / or after determining the increase in the ambient air pressure, the compression ratio of the charge in the combustion chamber is reduced or that after determining the reduction in the temperature, the compression ratio of the charge in the combustion chamber is reduced and / or after detecting the increase in the temperature Compression ratio of the charge in the combustion chamber is increased.

7. A method for operating an internal combustion engine according to claim 1,

characterized

a pressure limit for the compressor is determined as a function of the air pressure prevailing in the surroundings of the internal combustion engine, and the method is carried out when a pressure to be generated by the compressor is beyond the pressure limit.

8. A method of operating an internal combustion engine according to claim 1,

characterized

that with constant power output and when changing the air pressure, so that the degree of delivery is changed, the compressor is operated with substantially unchanged parameters.

9. A method for operating an internal combustion engine according to claim 1,

characterized

the air pressure prevailing in an environment of the internal combustion engine is measured with a pressure sensor and / or the temperature prevailing in an environment of the internal combustion engine is measured with a temperature sensor.

10. Internal combustion engine with a control unit with a computer,

characterized

that in a memory of the computer of the control unit, a program is stored, which has at least one subsection, in whose execution the

Internal combustion engine is operated by a method according to one of the preceding claims.