DE102012012748A1 - Operating method of a combustion chamber comprising an internal combustion engine - Google Patents

Abstract

The invention relates to an operating method of an internal combustion engine (1) comprising a combustion chamber (2) with a first and a second operating state, between which the internal combustion engine (1) can be switched, comprising the following steps: a) main ignition, in particular external ignition of one in the combustion chamber (2 ) existing fuel-air mixture, b) subsequent injection of a predetermined amount of fuel into the combustion chamber (2), c) re-ignition of the fuel subsequently injected into the combustion chamber (2), steps b) and c) only in the second Operating state are carried out.

Description

The present invention relates to operating methods of a combustion chamber comprising a combustion engine according to the preambles of claims 1 and 2. Furthermore, the invention according to the preamble of claim 8 an internal combustion engine with a first and a second operating state, between which the internal combustion engine for application of the operating method according to the invention switchable is.

From the DE 10 2010 032 431 A1 An operating method for operating an internal combustion engine is known according to which a lean fuel-air mixture injected in a combustion chamber of the internal combustion engine is initially spark-ignited. A residual amount of air remaining in the combustion chamber after the external ignition is subsequently at least partially combusted by the subsequent injection of a predetermined quantity of fuel and by subsequent ignition of this subsequently injected fuel. In this way, it can be ensured that a vehicle catalytic converter downstream of the internal combustion engine for exhaust gas treatment, in particular during a warm-up phase of the internal combustion engine, is heated up so that the catalytic converter reaches its preferred operating temperature particularly quickly, at which point it generates exhaust gas generated by the internal combustion engine can purify effective way.

Conventional operating methods for internal combustion engines, however, have the disadvantage that they are designed in particular with respect to different operating conditions of vehicle components, such as an exhaust gas turbocharger or an exhaust gas catalyst, which are in communication with the internal combustion engine, not flexible enough to be on Changes in the operating conditions of such vehicle components to respond.

Conventional operating methods may include, for example, HCCI combustion or room-temperature combustion (RZV), stratified or semi-stratified combustion (DES, HOS), homogeneous combustion or low NOx combustion (NAV) for direct injection internal combustion engines.

Some of these combustion processes have an excess of air in the combustion chamber. Among other things, the excess air in the combustion chamber, especially at low speeds to low enthalpy in the exhaust gas or in the exhaust gas mass flow, so that an exhaust gas turbocharger shows little effect, which sets only a low torque and thus a poor dynamic response.

Under operating condition may also be an optimum operating temperature of an exhaust gas catalyst of the internal combustion engine to be meant, which is not sufficiently high, for example, after a long idle state of the internal combustion engine to ensure effective cleaning of the exhaust gas catalyst supplied exhaust gases.

Low-energy exhaust gas enthalpy, in particular with low-displacement internal combustion engines, leads to disadvantages with regard to the dynamic behavior of the internal combustion engine and the operating temperature of the exhaust gas catalytic converter at low rotational speeds. Downsizing, which leads to smaller displacement engine, is operated to reduce overall CO ₂ emissions. Displacement small internal combustion engines have a lower absolute friction power compared to larger displacement engine, so that, especially in combination with a supercharging of the internal combustion engine, the fuel consumption can be reduced, causing the CO ₂ emissions decrease.

It is therefore an object of the present invention to provide an improved embodiment in which the abovementioned disadvantages are eliminated or at least reduced.

Said object is achieved by a method according to independent claims 1 and 2 and by a device according to independent claim 8. Preferred embodiments are the subject of the dependent claims.

According to the operating method according to the invention of a combustion engine comprising a combustion chamber, the internal combustion engine has a first and a second operating state, between which it can be switched.

In the event that the internal combustion engine is in the first operating state, the operating method according to the invention comprises the step a) of the main ignition of a fuel-air mixture present in the combustion chamber. The process steps b) and c) to be explained below are not executed in the first operating state.

In the event that the internal combustion engine is in the second operating state, according to the operating method according to the invention in addition to the main ignition according to step a) additionally the steps b) of the subsequent injection of a predetermined amount of fuel in the combustion chamber, and c) the Nachzündens of executed in the combustion chamber subsequently injected fuel.

The switching of the internal combustion engine from the first to the second operating state and conversely, depending on various parameters, for example as a function of an operating condition of a vehicle component operatively connected to the internal combustion engine, this can take place.

The operating method according to the invention in the first operating state of the internal combustion engine is characterized in that the fuel consumption of the internal combustion engine for the implementation of the operating method is relatively low, since fuel is consumed only in the main ignition according to step a).

However, in the first operating state of the internal combustion engine, only a relatively small torque can be generated in conjunction with an exhaust gas turbocharger downstream of the internal combustion engine since the turbine of the exhaust gas turbocharger due to the so-called "turbo lag" at low engine speed no high turbines Can produce power.

By switching the internal combustion engine in the second operating state due to the associated subsequent injection of fuel and its afterburning in the combustion chamber according to the process steps b) and c) generates an additional amount of exhaust gas with an additional exhaust enthalpy due to the associated additional combustion. At the same time, an exhaust gas temperature of the exhaust gas is increased.

The additional exhaust gas enthalpy can be used by one of the internal combustion engine downstream exhaust gas turbocharger to generate an additional turbine power, so that ultimately increases the delivered from the engine total torque.

It can also be switched from the first to the second operating state, if during a warm-up phase of the internal combustion engine, a vehicle downstream of the engine catalytic converter should reach its optimum operating temperature for the purification of exhaust gas as quickly as possible. After reaching the optimum operating temperature of the vehicle catalytic converter, the internal combustion engine can be switched back into the first operating state to reduce fuel consumption.

According to the invention, in order to ensure the generation of a particularly large amount of additional exhaust gas enthalpy, the steps b) or c) can be carried out essentially during a period in which both an inlet valve for supplying air into the combustion chamber and an outlet valve for discharging of exhaust gas generated in the combustion chamber is at least partially open and a positive purge gradient prevails. The simultaneous at least partial opening of inlet valve and outlet valve in conjunction with a positive pressure gradient between an air supply line for supplying air into the combustion chamber and an exhaust pipe for discharging generated in the combustion chamber exhaust gas of the internal combustion engine, virtually leads to a "flushing" of the combustion chamber with air. In this way, after carrying out the step a) of the main ignition according to the invention, a particularly large amount of air is introduced into the combustion chamber, which is then available for the subsequent injection and subsequent ignition according to steps b) and c) according to the invention.

In an alternative operating method according to the invention, after the main ignition of the fuel-air mixture according to step a) a residual amount of air remain in the combustion chamber and in step b) subsequently the predetermined amount of fuel are injected into the combustion chamber and in step c) the rest air quantity at least partially burned. Advantageously, this alternative operating method can be used in particular for lean fuel-air mixtures, so that after the main ignition, the remainder of the air quantity remains in the combustion chamber, whereby the air present in the combustion chamber is used effectively. Preferably, the implementation of steps b) and c) substantially during a period in which a piston moves in the direction of its bottom dead center due to the main ignition according to step a).

Preferably, the method of operation is periodically repeated, one period having a first period in which the internal combustion engine is in the first mode and a second period in which the internal combustion engine is in the second mode, the first period equaling the second period or, alternatively, the first period period is greater than the second period period or, alternatively, the first period period is less than the second period period.

This makes it possible, by a suitable choice of the duration of the first or second period, in particular relative to each other, an additional amount of exhaust gas and thus an additional exhaust enthalpy due to the additional inventive steps b) and c) of the subsequent injection or Nachzündens of fuel generate, with the amount of additional exhaust gas can be adjusted by appropriate choice of the first and second period period. The same applies to one with the additional steps b) and c) associated increase in the temperature of the exhaust gas generated in the internal combustion engine.

In a further embodiment, the internal combustion engine further comprises an exhaust system connected downstream of the combustion chamber with an exhaust gas catalyst for purifying exhaust gas generated in the combustion chamber, wherein the internal combustion engine is operatively connected to the first exhaust gas in dependence on an exhaust gas temperature of the exhaust gas received in the exhaust gas catalyst second operating state is switched. In this way, it can be ensured that the exhaust gas temperature-dependent operating temperature of the exhaust gas catalyst can be maintained in a temperature range in which the exhaust gas catalyst purifies the exhaust gas generated in the combustion chamber of the internal combustion engine in a particularly effective manner.

In a particularly preferred embodiment, the internal combustion engine is switched to the first operating state when the exhaust gas temperature exceeds a first predetermined temperature threshold and switched to the second operating state when the exhaust gas temperature falls below a second temperature threshold. In this way, the temperature dependent on the exhaust gas temperature operating temperature of the exhaust gas catalyst can be maintained in a predetermined temperature interval, in which the exhaust gas catalyst particularly effectively cleans the absorbed exhaust gas.

• – Sauerstoffgehalt in dem von der Brennkraftmaschine erzeugten Abgas,
• – Luftgehalt in dem von der Brennkraftmaschine erzeugten Abgas,
• – Motorlast oder/und momentane Drehzahl der Brennkraftmaschine,
• – Schichtungsgrad oder/und Homogenisierung des von der Brennkraftmaschine erzeugten Abgases.

In accordance with step c), the after-ignition preferably takes place in a time-delayed manner relative to the subsequent injection according to step b) of the operating method according to the invention, such that a duration of the time offset is defined or determinable in dependence on one or more of the following parameters:

• Oxygen content in the exhaust gas produced by the internal combustion engine,
• Air content in the exhaust gas produced by the internal combustion engine,
• Engine load and / or instantaneous speed of the internal combustion engine,
• Lining degree and / or homogenization of the exhaust gas generated by the internal combustion engine.

The invention further relates to an internal combustion engine with a first and a second operating state, between which the internal combustion engine for use of a method with one or more of the above features is switchable.

It is understood that the features mentioned above and also the features mentioned below can be used within the scope of practicability not only in the respectively indicated combination but also in other combinations or alone, without departing from the scope of the present invention.

Other important features, advantages and aspects of the invention will become apparent from the dependent claims, from the drawings and from the associated subsequent description part, are explained in the preferred embodiments of the invention with reference to the drawings.

In each case show schematically:

1 An embodiment of the internal combustion engine according to the invention,

2 a first embodiment of the operating method according to the invention,

3 A second embodiment of the operating method according to the invention and

4 a state diagram for various components of the internal combustion engine in carrying out the operating method according to the invention.

In the 1 is an internal combustion engine according to the invention with 1 designated. The internal combustion engine 1 has a combustion chamber 2 in which a piston 3 is arranged translationally movable between an upper and a lower dead center. The internal combustion engine 1 further comprises an air supply line 4 for supplying air into the combustion chamber 2 , as well as an exhaust pipe 5 for discharging in the combustion chamber 2 generated exhaust gas. The internal combustion engine 1 can also be an injection system for injecting fuel into the combustion chamber 2 include. The injection system may include a control device for controlling the injection of fuel into the combustion chamber 2 exhibit. Furthermore, the internal combustion engine 1 also an ignition device for one in the combustion chamber 2 formed mixture of air and fuel. Conceivable are conventional ignition devices with single-spark ignition systems, multi-spark, high-frequency or Corona ignition systems, as well as laser ignition systems or ignition by means of a glow plug. Also, the ignition device may include a control device for controlling the ignition of fuel in the combustion chamber 2 exhibit.

The the combustion chamber 2 via the air supply line 4 deliverable amount of air can by means of a movable between an open and closed position inlet valve 6 be set. Accordingly, the amount of out of the combustion chamber 2 over the exhaust pipe 5 discharged exhaust gas by means of a between an open and closed position movable exhaust valve 7 be set. It is also conceivable to provide a variable valve train which allows the phase position and / or opening duration and / or lifting height of the inlet valve 6 and exhaust valve 7 free to set.

Furthermore, an exhaust turbocharger 8th with the exhaust pipe 5 in fluid communication. The exhaust turbocharger 8th may have an exhaust gas turbine, the exhaust enthalpy of the in the combustion chamber 2 used exhaust gas to one in the air supply line 4 arranged compressor (in the 1 not shown) of the exhaust gas turbocharger for increasing the performance of the internal combustion engine 1 to drive in a conventional manner.

Furthermore, the internal combustion engine 1 an exhaust gas catalyst 9 include, which with the exhaust turbocharger 8th , or, if the internal combustion engine is not an exhaust turbocharger 8th has, directly to the exhaust pipe 5 is in fluid communication. By means of the exhaust gas catalyst 9 can that be in the combustion chamber 2 generated exhaust gas after treatment and cleaned.

The internal combustion engine 1 can also have a device that allows you to adjust the compression variable. Such devices are also known under the name VCR (variable compression ratio).

In the presentation of the 2 shows a first embodiment of a temporal course of the operating method according to the invention. As from the representation of 2 The internal combustion engine becomes apparent 1 operationally periodically switched between the first (I) and second (II) operating state. The internal combustion engine 1 is thus during the period 12 a period 11 in the first (I) operating state and during the period of time 13 the period 11 in the second (II) operating state. The first period 12 can do it like in the 2 shown in time equal to the second period period 13 but in variants it is of course also possible that the first period period 12 greater or longer than the second period period 13 is or vice versa.

By a suitable definition of the first and second period periods 12 . 13 in which the internal combustion engine 1 is in the first and second operating state, both an exhaust gas temperature in the combustion chamber 2 the internal combustion engine 1 generated exhaust gas as well as by means of the process steps b) and c) of the additional injection and Nachzündens generated additional amount of exhaust gas enthalpy be adjusted and corrected in a flexible manner.

This can be the duration of the period 11 or the period periods 12 and 13 at any time depending on external parameters, such as an operating condition of the exhaust gas turbocharger 8th or the exhaust gas catalyst 9 , adapted and changed.

In the 3 is the time course 10 ' the operating states of the operating method according to the invention for the internal combustion engine according to a second embodiment shown in which the internal combustion engine 1 operationally in dependence on the exhaust gas temperature T _{exhaust gas} in the exhaust gas catalyst 9 (see. 1 ) is switched from the first to the second operating state and vice versa.

The switching of the internal combustion engine 1 from the second (II) in the first operating state (I) takes place when the exhaust gas temperature T _exhaust exceeds a first predetermined temperature threshold S ₁ . Accordingly, a changeover from the first (I) to the second (II) operating state takes place when the exhaust gas temperature T _{exhaust gas falls} below a second temperature threshold value S ₂ . The switching of the operating states in dependence on the temperature thresholds S ₁ , S ₂ is in the 3 based on the graph 13 shown.

In this way, it can be ensured, for example, that the temperature of the exhaust gas T _{exhaust gas} and thus also the operating temperature of the internal combustion engine that depends on it 1 downstream exhaust gas catalyst 9 remains within a predetermined temperature interval in which the exhaust gas catalyst 9 that in the combustion chamber 2 the internal combustion engine 1 generated exhaust most effectively cleans.

In the presentation of the 4 Now, a preferred variant of the embodiment is shown in which the implementation of steps b) and / or c) of the inventive subsequent injection or Nachzündens takes place during a period in which both the inlet valve 6 as well as the exhaust valve 7 at least partially open. This fact is evident from the presentation of the 4 clearly, in which a temporal course 15 an opening degree of the exhaust valve 7 and a time course 16 an opening degree of the intake valve 6 is shown.

The chronological course of the pressure in the combustion chamber 2 in the combustion mode of the internal combustion engine 1 is in the 4 With 17 in which additionally the top dead center (TDC) of the piston 3 in which the combustion chamber 2 a minimal Has volume with 22 is designated during the bottom dead center (UT) of the piston 3 in which the combustion chamber 2 having a maximum volume, with 23 is designated. The top dead center 22 and bottom dead center 23 are in the 4 shown as an example. Depending on the operating point of an internal combustion engine, the degree of opening of the valves 6 and 7 and / or the pressure curve 17 in the combustion chamber 2 to vary this. The opening degrees of the valves can be influenced by the variable valve operation, which also influences the pressure curve 17 in the combustion chamber 2 to have. The pressure gradient 17 can also be affected by variable compression (VCR), for example by increasing the compression at low loads, so that there is an improved implementation of the injected fuel, which reduces fuel consumption and emits less CO2. Furthermore, a throttle valve or a throttle element in air supply line 4 be provided to the deliverable amount of air and thus the available combustion air in the combustion chamber 2 in addition to control.

The maximum lift of the exhaust valve 7 is with 20 denotes the maximum lift of the intake valve 6 is with 21 designated. A preferred period for the implementation of steps b) and / or c), in which therefore both the inlet valve 6 as well as the exhaust valve 7 is at least partially open, is in the presentation of 4 With 18 designated. In this overlapping phase it comes with a positive purging gradient to a "flushing" or "scavenging" of the combustion chamber 2 with air. Advantageously, with an additional injection or subsequent injection of fuel during the valve overlap phase, the oxygen content in the exhaust gas can be reduced, so that the internal combustion engine in the main heat conversion point around top dead center 23 optimal efficiency, ie usually low exhaust gas temperatures, can be operated, whereby the fuel consumption decreases and at the same time a high exhaust gas temperature can be achieved in conjunction with a high exhaust gas flow rate. Furthermore, the catalyst can be protected against excessive oxidation by the proportion of air in the exhaust gas. Too high a proportion of air in the exhaust gas would lead to a temperature increase in the catalyst, which ultimately leads to the destruction of the catalyst.

In a further variant of the embodiment, as shown in 4 the inventive steps b) and c) of the subsequent injection or Nachzündens also in the with 19 designated period in which the piston 3 due to the main ignition according to step a) in the direction of bottom dead center 23 moved and / or the exhaust valve 7 already partially open (see opening degree 15 the exhaust valve).

It is also conceivable in the exhaust pipe 5 another ignition source, next to the ignition source for the combustion chamber 2 to provide. This may differ from the ignition source for the combustion chamber 2 differ. Here, the further ignition source each cylinder, one cylinder bank or after the merger of two or more cylinders in the exhaust pipe 5 be assigned.

In addition to steps a), b) and c) of the operating method according to the invention, it is possible in each case dynamically to set the amount of the fuel to be injected, the time of the injection and the time of ignition of steps a), b) and c) such that an im Substantially constant exhaust gas volume flow and / or constant exhaust gas temperature and / or constant oxygen content in the exhaust gas can be set or the exhaust gas volume flow and / or the exhaust gas temperature and / or the oxygen content in the exhaust gas can be modeled in time.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 102010032431 A1 [0002]

Claims (8)

Operating method of a combustion chamber ( 2 ) comprehensive internal combustion engine ( 1 ) with a first (I) and a second (II) operating state, between which the internal combustion engine ( 1 ), comprising the following steps: a) main ignition, in particular external ignition, of one in the combustion chamber ( 2 ) present fuel-air mixture, b) subsequent injection of a predetermined amount of fuel into the combustion chamber ( 2 ), c) after-ignition of the into the combustion chamber ( 2 ) subsequently injected fuel, wherein steps b) and c) are carried out only in the second operating state (II), characterized in that the execution of steps b) and c) substantially during a period ( 18 ), in which both an inlet valve ( 6 ) for supplying air into the combustion chamber ( 2 ) as well as an exhaust valve ( 7 ) for discharging in the combustion chamber ( 2 ) is at least partially open and a positive purge gradient prevails. Operating method of a combustion chamber ( 2 ) comprehensive internal combustion engine ( 1 ) with a first (I) and a second (II) operating state, between which the internal combustion engine ( 1 ), comprising the following steps: a) main ignition, in particular spark ignition, in the combustion chamber ( 2 ) present fuel-air mixture, b) subsequent injection of a predetermined amount of fuel into the combustion chamber ( 2 ), c) after-ignition of the into the combustion chamber ( 2 ) subsequently injected fuel, wherein the steps b) and c) are carried out only in the second operating state (II), characterized in that after the main ignition of the fuel-air mixture according to the step a) a balance of air volume in the combustion chamber ( 2 ) remains and in step b) subsequently the predetermined amount of fuel in the combustion chamber ( 2 ) is injected and in step c) the residual amount of air is at least partially burned. Operating method according to claim 2, characterized in that the execution of steps b) and c) substantially during a period ( 19 ), in which a piston ( 3 ) due to the main ignition according to step a) in the direction of its bottom dead center ( 23 ) emotional. Operating method according to one of Claims 1 to 3, characterized in that the operating method is periodically repeated in operation, one period ( 11 ) a first period ( 12 ), in which the internal combustion engine ( 1 ) is in the first (I) operating state, and a second period ( 13 ), in which the internal combustion engine ( 1 ) in the second (II) operating state, wherein the first period ( 12 ) equal to the second period ( 13 ) or the first period ( 12 ) greater than the second period ( 13 ) or the first period ( 12 ) smaller than the second period ( 13 ). Operating method according to one of claims 1 to 4, characterized in that the internal combustion engine ( 1 ) further to the combustion chamber ( 2 ) downstream exhaust system with an exhaust gas catalyst ( 9 ) for cleaning in the combustion chamber ( 2 ), wherein the internal combustion engine ( 1 ) operatively in dependence on an exhaust gas temperature (T _{exhaust gas} ) of the in the exhaust gas catalyst ( 9 ) is switched to the first (I) or second (II) operating state. Operating method according to claim 5, characterized in that the internal combustion engine ( 1 ) is switched to the first (I) operating state when the exhaust gas temperature exceeds a first predetermined temperature threshold (S ₁ ), and is switched to the second (II) operating state, when the temperature of the vehicle in the catalyst ( 9 ) absorbed exhaust gas falls below a second temperature threshold (S ₂ ). Operating method according to one of the preceding claims, characterized in that the post-ignition according to step c) is carried out offset in time to the subsequent injection according to step b), that a duration of the time offset depending on one or more of the following parameters is set or definable: - Oxygen content in one of the internal combustion engine ( 1 ) produced exhaust gas - air content in one of the internal combustion engine ( 1 ) produced exhaust gas - engine load and / or instantaneous speed of the internal combustion engine ( 1 ) - degree of stratification or / and homogenization of the of the internal combustion engine ( 1 ) generated exhaust gas. Internal combustion engine ( 1 ) with a first (I) and a second (II) operating state, between which the internal combustion engine for use in a method according to one of the preceding claims is switchable, comprising: - a combustion chamber ( 2 ), - an inlet valve ( 6 ) for supplying air into the combustion chamber ( 1 ) - an outlet valve ( 7 ) for removing exhaust gases from the combustion chamber ( 2 ), - an injection system for injecting fuel into the combustion chamber ( 2 ), wherein the injection system after a main ignition of a fuel-air mixture present in the combustion chamber, an optional subsequent injection of a predetermined amount of fuel into the combustion chamber ( 2 ) and the subsequent optional injection of the following into the combustion chamber ( 2 ) introduced fuel in the combustion chamber ( 2 ) existing air quantity is burned, characterized in that the optional subsequent injection and the subsequent optional subsequent ignition take place only in the second operating state (II).

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