DE102007052157A1 - Internal combustion engine operating method for vehicle, involves exhausting exhaust gas from cylinder using exhaust gas section of internal combustion engine, and increasing amount of air led via section dependent on condition of section - Google Patents

Abstract

The method involves supplying air into a cylinder (2) using a suction tube (9) of an internal combustion engine (1). Exhaust gas is exhausted from the cylinder using an exhaust gas section (12) of the engine. An amount of air led through the gas section is increased dependent on a condition of the gas section. The condition of the gas section is determined as a temperature of the exhaust gas and/or as the temperature of components arranged in the gas section. An air-fuel-ratio is increased with an equal torque by increasing quantity of air supplied into the tube. An independent claim is also included for a computer program for operating an internal combustion engine.

Description

Technical area

The Invention relates to a method for operating an internal combustion engine, and an internal combustion engine, in particular an internal combustion engine with an active air supply device.

State of the art

at usual Internal combustion engines become an air-fuel mixture in cylinders burned and over an exhaust system is ejected according to exhaust gases. The supplied to the cylinders Air volume is determined by the cylinder piston at a certain speed exercised Suction and the position of a throttle valve, which in the intake section of the internal combustion engine is arranged. For vehicles with one Charging can also affect the amount of air by changing the charge become.

Depending on the desired torque specified by the driver is taken into account of the desired Mixture (typically Lambda = 1) to make the engine exhaust optimal to operate) determines the amount of air supplied. Accordingly, will an air quantity actuator, d. H. the throttle and / or a Charging set and there is an actual amount of air in the Cylinders. The wished Mixture then determines the amount of fuel to be injected.

Depending on the temperature of the exhaust gases emitted from the combustion chambers are components in the exhaust section, such. Manifold, catalyst and turbocharger, exposed to thermal stress. Especially at a high Engine load is the temperature of the exhaust gases so high that in the exhaust section arranged elements damaged can be unless further action for cooling the exhaust gases or arranged in the exhaust section elements provided are.

A Possibility, to reduce the temperature in the exhaust section of an internal combustion engine, there is in greasing the air-fuel mixture, d. H. the ratio of Amount of injected fuel to the air charge amount to increase. This makes it possible the exhaust gases through the addition injected fuel z. B. by the low temperature of provided fuel or by the absorbed evaporation energy cool. The disadvantage, however, that thereby fuel consumption is increased and thus additional Costs arise. Continue to get unburned fuel or Pollutants such as CO and HC in the environment.

There by enriching the air-fuel mixture at constant air filling the output torque increases up to a λ of about 0.9 a special adaptation of one or more air quantity actuators and fuel quantities to be injected in order to achieve the above measure Reduction of the exhaust gas temperature as possible perform torque neutral to be able to.

It It is an object of the present invention to provide a method of operation an internal combustion engine to provide, in the components in the exhaust section of the internal combustion engine against excessive thermal stress protected can be and further wherein the amount of emitted pollutants C0 and HC is essentially not opposite the normal operation of the engine is increased and the fuel consumption across from the conventional one Component protection is reduced.

Disclosure of the invention

These Task is by the method for operating an internal combustion engine according to claim 1 and by the internal combustion engine according to the independent Claim solved.

Further advantageous embodiments of the invention are specified in the dependent claims:
According to one aspect, a method for operating an internal combustion engine having an air supply section for supplying air and an exhaust section for discharging exhaust gas is provided, wherein the amount of air guided through the exhaust section is increased depending on a state of the exhaust section.

The The above method therefore provides that moved through the exhaust section Increase airflow and over the additional Air whose temperature corresponds to an ambient temperature of the internal combustion engine, so cooler is the temperature of the exhaust gas, located at the exhaust section Cool components down.

Farther can be provided that dependent from the condition of the exhaust portion, the air-fuel ratio at constant torque by increasing the amount of in the air supply section supplied Air increased is to increase the amount of air transported through the cylinder.

As a result, the amount of air moved through the cylinders can be increased in relation to that for normal operation of the internal combustion engine in the predetermined speed range or load torque range. Due to the extra air, its tempera corresponds to an ambient temperature of the internal combustion engine, that is cooler than the temperature of the exhaust gas, a component located in the exhaust section can be cooled down. Due to the additional amount of air, the internal combustion engine is operated in an operating state λ <1. The cooling effect in the exhaust section is created by the entrainment of the excess air masses, whereby the thermal energy distributed to a correspondingly greater mass and thus the temperature of the exhaust gas is lowered.

Farther For example, the state of the exhaust gas portion may be the temperature of the exhaust gas and / or as the temperature of one or more in the exhaust section arranged components are determined.

According to one embodiment can the amount of fed Air increased be by opening an opening a throttle in the air supply part is enlarged or by a pressure in the air supply part, especially in a suction pipe, is increased.

Farther can in a first mode depending on a state of Exhaust section the air-fuel ratio with the same torque by elevating the amount of in the air supply section supplied Air increased to increase the amount of air transported through the cylinder, and in a second mode dependent from another state of the exhaust section, the air-fuel ratio at constant torque by increasing the amount of fuel supplied be reduced by the amount of fuel transported by the cylinder to increase.

According to one embodiment can be between the first and the second mode, depending on a temperature of a component in the exhaust section, switched so that as a result of switching the temperature of the component one Limit does not exceed.

Farther can be method dependent from the state of the exhaust section through an air supply air be introduced into the exhaust section to in the exhaust section the guided Increase air volume. In this way, the temperature of the exhaust line without impairment of engine operation by supply from additional Air can be reduced.

According to one Another aspect is an engine controller for operating an internal combustion engine with an air supply section for feeding provided by air and an exhaust section for discharging exhaust gas, wherein the engine controller is configured to be dependent on a state of Exhaust section the air-fuel ratio at the same Torque by increasing the amount of added To raise air, so that the amount of air transported through the cylinder is increased.

The Motor control may be configured to operate in a first mode dependent from a state of the exhaust portion, the air-fuel ratio at constant torque by increasing the amount of air supplied to increase, so that the amount of air transported through the cylinder is increased, and in a second mode depending on another state the exhaust section the air-fuel ratio at the same Torque by increasing the amount of supplied To degrade fuel so that the transported through the cylinder Fuel quantity increased becomes. The engine controller may be further configured to intervene the first and the second mode depending on a temperature of a component in the exhaust section, to switch so that as a result of the switching the temperature of the component does not exceed a limit.

According to one Another aspect is an engine system with an above engine control and an internal combustion engine having an air supply section for feeding hen vorgese of air and an exhaust section for discharging exhaust gas wherein the engine controller is configured, an opening of a throttle valve to enlarge or a pressure in the air supply section, especially in a suction pipe, increase the amount of air supplied to increase.

According to one Another aspect is an engine controller for operating an internal combustion engine with an air supply section for feeding provided by air and an exhaust section for discharging exhaust gas, being an air supply for feeding is provided by air in the exhaust section, wherein the engine control is trained to be dependent from a state of the exhaust section through the air supply air in the exhaust section to bring in the exhaust section the guided Increase air volume.

According to one Another aspect is a computer program is provided, the program code contains which, when executed on a data processing unit, performs the above method.

Brief description of the drawings

preferred embodiments The invention will be described below with reference to the accompanying drawings explained in more detail. It demonstrate:

1 a schematic representation of an engine system according to an embodiment of the invention;

2 a schematic representation of an engine system according to another embodiment of the invention;

3 a torque λ diagram for representing the output torque from an engine at different λ values of the air-fuel mixture; and

4 a schematic representation of an engine system according to another embodiment of the invention.

Embodiments of the invention

preferred embodiments will be explained in more detail below described. The same reference numerals correspond to elements of the same or comparable function.

In 1 shows a schematic representation of an internal combustion engine 1 with a cylinder 2 which is controlled by a motor control 3 operated according to a four-stroke principle. For simplicity, there is only one cylinder 2 of the internal combustion engine 1 shown. It can be any number of cylinders 2 in the internal combustion engine 1 be provided.

The combustion chamber 4 of the cylinder 2 is controlled by the engine control 3 , via an injection nozzle 5 Fuel and via an inlet valve 6 Air supplied to then z. B. with the help of a spark plug 7 to trigger a burning process. The method described below can also be applied to compression ignition engines, so that the provision of the spark plug 7 is not necessary. The lifting movement of a piston 8th in the cylinder 2 causes at an open inlet valve 6 a suction of air through the suction pipe 9 , In the suction pipe 9 is to control the in the cylinder 2 flowing air mass a throttle 10 arranged, their position by the engine control 3 is determined.

Exhaust gases, which arise during a burning process, are at a subsequent piston stroke of the piston 8th in the cylinder 2 via the outlet valve 11 in an exhaust section 12 of the internal combustion engine 1 issued. In the exhaust section 12 the internal combustion engine is z. As a catalyst 13 for converting pollutants into environmentally less harmful substances.

The operation of the internal combustion engine 1 is through the engine control 3 usually controlled so that the internal combustion engine 1 operated as optimal as possible, that is, the engine control determines the in the cylinder 2 injecting fuel quantity corresponding to the air mass flowing into the cylinder to obtain a stoichiometric balance, which is denoted by λ = 1. At the stoichiometric equilibrium for gasoline is the air mass in the combustion chamber of the cylinder 2 about 14.7 times the mass of injected fuel. With regard to this value, the fuel quantity increases compared to the air mass in the combustion chamber 4 , so we speak of a rich air-fuel mixture (air-fuel ratio) and λ is smaller than 1. Is compared to the stoichiometric equilibrium, the air mass against the mass of the injected fuel in the combustion chamber 4 increased, one speaks of a lean air-fuel mixture (air-fuel ratio) in the combustion chamber 4 and λ becomes larger 1.

Under high load, the amount of fuel injected is high and the temperature of the exhaust gases entering the exhaust section 12 of the internal combustion engine 1 is correspondingly also high, especially in comparison to an operation of the internal combustion engine at a lower load or at idle. The high exhaust gas temperature has a negative effect on the service life of the exhaust section 12 of the internal combustion engine 1 arranged elements such. B. manifold, catalyst 13 and the like, and may even damage them. It is therefore necessary to ensure that the exhaust gas temperature does not exceed a certain value or only for a short time, so that the life of the exhaust section 12 provided components is not affected. According to the invention it is therefore provided that the engine control the internal combustion engine 1 so that operates from the out of the combustion chamber 4 discharged exhaust gases are cooled by an additional measure, if there is a risk that the temperature of the exhaust gases in normal engine operation (eg at λ = 1) are too high.

The engine controller therefore controls the internal combustion engine 1 so that the amount of air passing through the cylinder 2 is moved, compared to the normal operation is increased. Because the air from the environment of the internal combustion engine 1 is sucked, this has the temperature of the environment of the internal combustion engine 1 and therefore can absorb part of the thermal energy of the exhaust gas. This lowers the temperature of the exhaust gas and thus protects the exhaust section 12 arranged elements.

The additional amount of air, for example, in the combustion chamber 4 get by the throttle 10 , controlled by the engine control 3 , continues to open without injecting additional fuel. As this reduces λ, this decreases from the internal combustion engine 1 provided drive torque initially to and at further Abmage tion takes that from the internal combustion engine 1 provided drive torque. This change in the drive torque can be compensated by a suitable adjustment of the amount of fuel to be injected in order to maintain the drive torque. However, the amount of air supplied to the cylinder can be increased to such an extent that, despite any fuel quantity that may have to be increased thereby, air is not required for the combustion process through the cylinder 2 and, on the other hand, the increased amount of fuel required to maintain the drive torque finds a corresponding amount of air to perform the combustion process.

Out 3 is a characteristic to be taken, the quality of the course of the internal combustion engine 1 provided drive torque with respect to the λ of the air-fuel ratio with the same amount of air indicates. The drive torque related to the amount of fuel (and thus the efficiency of the engine) has the maximum in the lean range (at λ <1).

2 shows a schematic representation of another embodiment of the invention, in which the same reference numerals correspond to elements of the same or comparable function. The embodiment of the 2 differs from the embodiment of the 1 in that an active air supply device in the intake of the internal combustion engine 1 is provided, which is the cylinder 2 provides air at an elevated pressure via the intake manifold. This has the advantage, compared to conventional naturally aspirated engines, that even at a maximum power level, that through the cylinder 2 guided air can still be increased. In conventional naturally aspirated engines, this is not possible because at the maximum power usually the throttle valve is fully or almost completely open, so that an increase in the air supply into the cylinder is not readily possible.

2 shows an active air supply device on the example of a turbocharger 15 which is driven by the exhaust gas stream in a suitable manner (not shown), and for this reason parts of the turbocharger 15 also in the exhaust section 12 are located. As well as the thermal capacity of the turbocharger 15 is limited, the turbocharger 15 also taken into account at the permitted maximum temperature of the exhaust gases.

A control of the boost pressure of the turbocharger 15 can be controlled by the engine control 3 z. B. by an air return from the suction pipe in the intake 16 of the turbocharger 15 with the help of a controllable return valve 17 be performed. By completely or partially closing this recirculation valve 17 In the return, the boost pressure increases in the intake manifold, and it is thus possible to the cylinder 2 to supply a larger air mass. Thus, it is possible even at a high load (ie high torque relative to maximum torque) of the engine 1 the amount of air for cooling in the exhaust section 12 further increase components. Alternatively or additionally, the boost pressure of the turbocharger 15 through a waste gate in the exhaust section.

In 4 another embodiment is shown. Like reference numerals correspond to elements of the same or comparable function.

The embodiment of the 4 differs from the previous embodiments in that additional air for cooling the exhaust gas portion and the components disposed therein is not through the cylinder 2 is directed, but controlled by the engine control 3 is fed directly to the exhaust section. This is an air supply 20 provided with the exhaust section 12 communicates and controlled by the engine control 3 Can introduce air. This makes it possible that the operation of the engine is not affected by the leaning of the air-fuel mixture.

The engine control 3 can be the introduction of air by means of the air supply 20 depending on a temperature in the exhaust section and in particular the temperature in the exhaust section in a predetermined for operation z. As the catalyst 13 keep optimal range.

Aspects of the methods for operating the internal combustion engines of the above-described embodiments will be described below. The provision of an additional amount of air for cooling the exhaust gases of the internal combustion engine 1 becomes at certain operating points or operating ranges of the internal combustion engine 1 performed, the z. B. depend on the exhaust gas temperature of the exhaust gas flowing from the cylinders. For this purpose, the exhaust gas temperatures are estimated according to a model of the engine, since usually no temperature sensor in the exhaust section 12 of the internal combustion engine 1 is provided. The model for determining the exhaust gas temperature considers z. B. at least one of the following variables: speed, air charge, lambda of the air-fuel mixture, injected fuel amount, speed curve and the like. Alternatively, of course, a temperature sensor in the exhaust section 12 be provided, the engine control 3 the current exhaust gas temperature tells. In particular, the additional amount of air may be provided if the exhaust gas temperature exceeds a predetermined limit.

Depending on the estimated over the model or detected exhaust gas temperature determines the engine control 3 , if and in what quantity additional air through the cylinder 2 is guided and whether and in what amount additional air in the exhaust gas section 12 is introduced to lower the exhaust gas temperature. If it is determined that additional air is needed to cool the exhaust gas, the engine control system ensures that 3 Continue making sure that even with extra through the cylinder 2 guided air, the torque of the internal combustion engine 1 remains constant, z. B. by the injected fuel amount is slightly increased.

When cooling with additional through the cylinder 2 Guided air not for each operating range of the internal combustion engine 1 is possible, the cooling of the exhaust gases in these operating ranges can also be realized by additional fuel is injected in place of the increased air supply to perform the combustion at a rich air-fuel ratio. This can lead to a first mode of operation, through additional, through the cylinder 2 cooled to a second mode, in which is cooled by additionally injected fuel, must be switched in order to obtain the desired cooling effect. When cooling with additional fuel, the heat of vaporization and the fuel located at ambient temperature cools the exhaust gas and thus causes the corresponding component protection in the exhaust section 12 ,

In such a switching between the first mode, ie the component protection by additional air supply, to the second mode, ie the component protection by supplying additional fuel, it must be noted, however, that after operating the internal combustion engine 1 in the first mode, combustion may occur in the catalyst due to the air now available in the region of the catalyst when unburned fuel now enters the catalyst. This releases heat and the temperature of the catalyst 13 increased accordingly. When switching from the first mode to the second mode, therefore, care must be taken that the temperature of the catalyst 13 has a sufficient temperature difference .DELTA.T to a maximum allowable temperature of the catalyst. For this reason, it can be provided that the switching point not only from the operating areas of the combustion engine 1 , but also on the temperature of individual components, such. As the catalyst, in the exhaust section depends.

Claims (12)

Method for operating an internal combustion engine ( 1 ) with an air supply section ( 9 ) for supplying air into a cylinder ( 2 ) and an exhaust section ( 12 ) for discharging exhaust gas from the cylinder ( 2 ), wherein, depending on a state of the exhaust gas section ( 12 ) passing through the exhaust section ( 12 ) guided amount of air is increased. Method according to claim 1, wherein the state of the exhaust gas section ( 12 ) as the temperature of the exhaust gas and / or as the temperature of one or more in the exhaust gas section ( 12 ) arranged components is determined. Method according to claim 1 or 2, wherein, depending on a state of the exhaust gas section ( 12 ) the air-fuel ratio is increased while maintaining the torque by increasing the amount of the air supplied to the air supply section in order to control the flow through the cylinder ( 2 ) to increase transported air volume. The method of claim 3, wherein the amount of air supplied is increased by opening an orifice of a throttle ( 10 ) in the air supply section ( 9 ) is increased or by a pressure in the air supply section ( 9 ), in particular in a suction tube, is increased. Method according to one of claims 3 to 4, wherein in a first operating mode depending on a state of the exhaust gas section ( 12 ) the air-fuel ratio is increased at constant torque by increasing the amount of air supplied to the cylinder through the ( 2 ) to increase transported air volume, and wherein in a second operating mode depending on a further state of the exhaust gas section ( 12 ) the air-fuel ratio is reduced while maintaining the torque by increasing the amount of fuel supplied to the by the cylinder ( 2 ) to increase transported amount of fuel. The method of claim 5, wherein between the first and second modes depending on a temperature of a component in Abgasab section ( 12 ), so that as a result of the switching, the temperature of the component does not exceed a threshold value. Method according to claim 1 or 2, wherein, depending on a state of the exhaust gas section ( 12 ) by an air supply air into the exhaust gas section ( 12 ) is introduced to in the exhaust section ( 12 ) increase the amount of air supplied. Motor control ( 3 ) for operating an internal combustion engine having an air supply section ( 9 ) for supplying air and an exhaust gas section ( 12 ) for discharging exhaust gas, wherein the engine control ( 3 ) is designed to be dependent on a state of the exhaust gas section ( 12 ) the air-fuel ratio at the same torque by increasing the amount of air supplied, so that the cylinder ( 2 ) transported air quantity is increased. Engine control according to claim 8, wherein the engine control ( 3 ) is configured to operate in a first operating mode as a function of a state of the exhaust gas section ( 12 ) to increase the air-fuel ratio while maintaining torque by increasing the amount of air supplied, so that through the cylinder ( 2 ) transported air volume is increased, and in a second mode depending on a further state of the exhaust gas section ( 12 ) to decrease the air-fuel ratio while maintaining torque by increasing the amount of fuel supplied, so that through the cylinder ( 2 ) transported amount of fuel is increased, the engine control ( 3 ) is further configured to switch between the first and the second operating mode as a function of a temperature of a component in the exhaust gas section (FIG. 12 ), so that as a result of the switching, the temperature of the component does not exceed a threshold. Engine system with a motor control ( 3 ) according to one of claims 8 to 9 and with an internal combustion engine ( 1 ) with an air supply section for supplying air to a cylinder ( 2 ) and an exhaust gas passage for discharging exhaust gas from a cylinder ( 2 ), wherein the engine control is formed, an opening of a throttle valve ( 10 ) or a pressure in the air supply section ( 9 ), in particular in a suction pipe, to increase the amount of air supplied. Motor control for operating an internal combustion engine ( 1 ) with an air supply section ( 9 ) for supplying air and an exhaust gas section ( 12 ) for discharging exhaust gas, wherein an air supply for supplying air into the exhaust gas section ( 12 ) is provided, wherein the engine control ( 3 ) is designed to be dependent on a state of the exhaust gas section ( 12 ) by the air supply air in the exhaust gas section ( 12 ) in order to 12 ) increase the amount of air supplied. Computer program containing a program code which, when running on a computing device, a method according to a the claims 1 to 6 executes.