WO2004022955A1

WO2004022955A1 - Internal combustion engine and method for the operation thereof

Info

Publication number: WO2004022955A1
Application number: PCT/EP2003/009276
Authority: WO
Inventors: Normann Freisinger; Martin Matt; Jörg WEINGÄRTNER
Original assignee: Daimlerchrysler Ag
Priority date: 2002-09-06
Filing date: 2003-08-21
Publication date: 2004-03-18
Also published as: EP1534947A1; DE10241443A1

Abstract

Disclosed is an internal combustion engine for a motor vehicle, comprising a starter system (14) and a control system (50) for controlling the internal combustion engine. The control system (50) of the internal combustion engine is configured for defined afterrunning of the internal combustion engine, by means of which pollutants that are left in the internal combustion engine are fed to the catalytic converter system (36) for afterburning, such that said control system (50) actuates the starter system (14) for a specific first period of time (t13) following a last combustion process (t1) in a combustion chamber (10).

Description

DaimlerChrysler AG

Internal combustion engine and method for operating the same

The invention relates to an internal combustion engine according to the preamble of patent claim 1 and a method for operating an internal combustion engine according to the preamble of patent claim 10.

Internal combustion engines of the type mentioned are already well known from the prior art. The internal combustion engines usually have a cylinder head, a cylinder crankcase connected to the cylinder head for receiving a common crankshaft and a plurality of pistons, and a plurality of combustion chambers delimited by the cylinder head, the cylinder crankcase and the respective pistons. Furthermore, several inlet channels for supplying a fuel-air mixture to the combustion chambers are connected to the cylinder head on the one hand and to an air intake pipe on the other, fuel being injected into the inlet channels in each case via an injection valve and the inlet channels each being closable via an inlet valve arranged in the cylinder head are. A throttle valve is provided in the air intake pipe to control the air supply. Likewise, a plurality of exhaust ports are connected to the cylinder head for discharging exhaust gases generated in the combustion chambers to form a catalyst system, the exhaust ports being closable in each case via an exhaust valve arranged in the cylinder head. A starter system for the starting process of the internal combustion engine is also coupled to the common crankshaft accommodated in the cylinder crankcase, and a controller controls all components of the internal combustion engine.

In addition to the exhaust gas limit values for motor vehicles, newer legal regulations also write limit values for the evaporation emissions from the motor vehicles, which arise in particular in the fuel system, the internal combustion engine (the engine), the transmission, the cooling and air conditioning system, etc. of the motor vehicle. These limit values have now reached an extremely low level, so that the evaporation emissions from the internal combustion engine are also relevant. The evaporation emissions are checked, for example, by a so-called SHED test, which is a type IV test according to EC Directive 70/220, version 96/99, to ensure compliance with the limit values for evaporation emissions.

To reduce pollutant emissions after switching off an internal combustion engine, it is already known, for example, from DE 197 35 455 Cl of the applicant, in which after switching off the internal combustion engine and checking whether the fuel injection is switched off, the throttle valve in the air intake pipe is opened at least approximately to the maximum, to cause ventilation of the combustion chambers and the exhaust system with fresh air supplied, through which pollutants are blown out of the internal combustion engine and afterburned in the still hot catalytic converter.

Starting from the aforementioned prior art, the present invention is therefore based on the object of further developing an internal combustion engine of the type mentioned at the outset in such a way that the evaporation emissions from the internal combustion engine are significantly reduced in a simple and reliable manner. Another object of the present invention is to provide a method for operating an internal combustion engine of the type mentioned at the outset, with which the evaporation emissions of the internal combustion engine are significantly reduced in a simple and reliable manner.

According to a first aspect of the invention, this object is achieved by an internal combustion engine having the features of patent claim 1. Advantageous configurations and further Formations of the invention are given in dependent claims 2 to 9.

The internal combustion engine has a cylinder head; a cylinder crankcase connected to the cylinder head for receiving a crankshaft and at least one piston; at least one combustion chamber delimited by the cylinder head, the cylinder crankcase and the respective piston; at least one inlet duct connected to a combustion chamber for supplying a fuel-air mixture; an air intake pipe connected to the at least one inlet duct; at least one exhaust duct connected to a combustion chamber for removing exhaust gases; a starter system coupled to the crankshaft disposed in the cylinder crankcase; and a controller for controlling the internal combustion engine. According to the invention, the controller is designed such that it actuates the starter system for a specific first period of time after a last combustion process in a combustion chamber.

By actuating the starter system after a last combustion process in a combustion chamber of the internal combustion engine, i.e. For example, if the driver requests the engine to be switched off, a defined overrun of the internal combustion engine is effected for a certain time. Through this wake, residues of hydrocarbon deposits in the intake / combustion tract of the internal combustion engine are conveyed into the still hot catalytic converter system and there are catalytically afterburned. Due to the reduced residues of hydrocarbon deposits in the internal combustion engine in this way, the internal combustion engine can be brought into a low-pollutant or almost pollutant-free state and the evaporation emissions can be significantly reduced accordingly.

In a particularly preferred exemplary embodiment of the invention, the internal combustion engine also has at least one supply device for secondary air, the supply device for secondary air having a valve device, which is preferably controllable by the engine control. The engine control preferably controls the valve device of the secondary air supply device such that secondary air is supplied to the internal combustion engine for a specific second period of time after a last combustion process in a combustion chamber. The supply of secondary air into the internal combustion engine results in an additional flushing of the corresponding components of the internal combustion engine, so that the pollutants which are still present in these components and are further conveyed by the wake of the internal combustion engine are fed to the still hot catalyst system for afterburning.

For example, the secondary air is supplied to the intake ducts, the combustion chambers, the exhaust ducts, an exhaust gas recirculation system, a catalyst system and the like of the internal combustion engine. The secondary air supply can take place, for example, by special designs of the exhaust gas flange or the cylinder head arrangement, as are known from DE 198 32 627 AI and DE 196 42 685 AI of the applicant.

The engine control advantageously controls the starter system such that the starter system, after the secondary air supply has been switched off, switches the internal combustion engine, i.e. especially the pistons in the cylinder crankcases, in an optimal starting condition.

To intensify the rinsing of the various components of the internal combustion engine with or without secondary air supply, a throttle valve is provided in a particularly preferred embodiment in the air intake pipe, which can be controlled by the engine control in such a way that the throttle valve is closed in a combustion chamber after the last combustion process. Due to the closed throttle valve, a negative pressure is generated in the internal combustion engine during the run-on of the internal combustion engine, which causes evaporation of hydrocarbon deposits from cracks and the like Recesses, for example, at transitions in the cylinder head, the valve seats and the piston rings favored. The pollutants released in this way are fed to the catalytic converter through the wake and possibly the secondary air supplied.

The throttle valve is preferably provided with sealing elements in such a way that it can be closed essentially gas-tight.

In order to avoid evaporation of hydrocarbons from the intake manifold through the internal combustion engine into the exhaust system even during the subsequent shutdown of the internal combustion engine, the throttle valve is preferably controlled by the engine control in such a way that the throttle valve remains in the closed position even after the specific first period of time.

According to a second aspect of the invention, the above-mentioned object is achieved by a method for operating an internal combustion engine with the features of patent claim 10. Advantageous refinements and developments of the method according to the invention are the subject of dependent claims 11 to 17.

The method for operating an internal combustion engine is characterized in that after a last combustion process in a combustion chamber, the starter system is actuated for a specific first period of time, so that a defined after-running of the internal combustion engine and thus significantly reduced evaporation emissions are effected, as explained above.

After a last combustion process in a combustion chamber, the internal combustion engine is preferably also supplied with secondary air for a specific second period in order to purge the respective components of the internal combustion engine and that Promote pollutants by supporting the wake in the catalyst system.

In the air intake pipe of the internal combustion engine, a throttle valve is preferably provided, which is closed in a combustion chamber after a last combustion process, so that a vacuum is generated in the internal combustion engine by the wake of the internal combustion engine with the advantages mentioned above.

The throttle valve preferably remains closed even after the defined overrun has ended, so that evaporation of hydrocarbon deposits from the intake manifold is prevented.

The above and further advantages and features of the invention are explained in more detail below on the basis of the description of a preferred exemplary embodiment with reference to the accompanying drawings. In it show:

Fig. 1 is a schematic representation of the Au construction

Internal combustion engine according to a preferred embodiment of the present invention; and

2a to 2f timing diagrams to explain the operation of the internal combustion engine of Fig. 1st

1 shows a schematic illustration of an internal combustion engine (in particular a reciprocating piston engine) of a motor vehicle. The structure basically corresponds to the previously known internal combustion engines, so that a detailed explanation of the structure and the mode of operation of the individual components is dispensed with in the context of this invention.

An essential part of the internal combustion engine is the cylinder head 11. The cylinder head 11 is in the usual way with the interposition of a cylinder head gasket connected to a cylinder crankcase 12, which receives a crankshaft and a plurality of pistons, the cylinder crankcase 12 and the cylinder head 11 in FIG. 1 extending substantially perpendicular to the plane of the drawing, so that only one piston can be seen in the cylinder crankcase 12. A plurality of combustion chambers 10 are defined or limited in a conventional manner by the cylinder head 11, the cylinder crankcase 12 and the pistons. The crankshaft accommodated in the cylinder crankcase 12 is coupled to a starter system or a starter / generator system 14, which serves to start the internal combustion engine in a known manner.

The combustion chambers 10 are each connected to an air intake pipe 18 via an inlet duct 16. The inlet channels 16 can each be closed or released by means of an inlet valve 20, which is controlled via a camshaft (not shown). An injection valve 22 for injecting fuel to generate a fuel-air mixture is provided in each of the inlet channels 16. A throttle valve 24 for controlling the air supply, a hot film air mass meter 26 and an intake manifold 28 are arranged in the air intake pipe 18 as part of an exhaust gas recirculation system. The fuel-air mixture introduced into the combustion chambers is ignited in each case by a spark plug 30.

The exhaust gases produced in the combustion process of the fuel-air mixture in the combustion chambers 10 are each discharged via an outlet channel 32. Analogously to the inlet channels 16, the outlet channels 32 can also be closed and released in each case via an outlet valve 34, which is controlled via a camshaft (not shown). The exhaust gases removed from the combustion chambers 10 are first fed to a catalyst system 36 for afterburning and finally released into the environment via the exhaust system 38. To further reduce the pollutants in the exhaust gases emitted by the exhaust system 38, the combustion chambers 10 removed exhaust gases in the usual way at least partially returned via an exhaust gas recirculation line 40 to the air intake pipe or the inlet channels 16 in order to pass through the combustion chambers 10 again. In addition to the exhaust gas recirculation line 40, the exhaust gas recirculation system also includes an exhaust gas recirculation valve 42, an electropneumatic changeover valve 44 and a negative pressure control 48 connected to the electropneumatic changeover valve 44 via a check valve for controlling the same, as shown in FIG. 1.

All components of the internal combustion engine are controlled by a suitable controller 50. For this purpose, the controller 50 is coupled not only to the components of the internal combustion engine already mentioned, but also to a large number of sensor devices. The sensor devices include, for example, the hot film air mass meter 26, a pressure sensor in the intake manifold 28, a first lambda probe 52 for detecting the oxygen content in the exhaust gases upstream of the catalyst system 36, a second lambda probe 54 for detecting the oxygen content in the exhaust gases after passing through the catalyst system 36, one Sensor device 56 for detecting the state of the catalyst system 36, a speed sensor 58, a sensor device 60 for detecting the crank angle of the crankshaft and the like.

In the exemplary embodiment of the internal combustion engine shown in FIG. 1, the control 50 is also designed such that it actuates the starter system 14 after a last combustion process in a combustion chamber 10, for example after detecting the driver's wish to switch off the engine. While a certain rotational energy leads to a certain overrun of the internal combustion engine even when conventional internal combustion engines are switched off, the operation of the starter system 14 causes a defined overrun for a certain predetermined period of time. The after-running of the internal combustion engine described in this way is preferably carried out by the operation of the starter system 14 as a function of the state of charge of the vehicle battery or of the on-board electrical system situation. In other words, in the case of a battery that is already too weak, such an after-run can be dispensed with in order to protect the battery.

Due to the defined after-running of the internal combustion engine, hydrocarbons, which are still located in the inlet channels 16, the combustion chambers 10 and the outlet channels 32, are fed to the still hot catalyst system 36, where they are combusted. In this way, the pollutants remaining in the internal combustion engine after the same has been switched off can be significantly reduced, which leads to significantly lower evaporation emissions from the internal combustion engine, as are demonstrated, for example, by so-called SHED tests.

In addition, the throttle valve 24 in the air intake pipe 18 is provided with sealing elements (not shown) in such a way that it can be closed essentially gas-tight. If the throttle valve 24 is closed during the overrun of the internal combustion engine described above, the operation of the starter system 14 creates a negative pressure in the internal combustion engine. This negative pressure promotes evaporation of hydrocarbons from cracks and the like recesses, for example at transitions in the cylinder head, the valve seats and the piston rings. The hydrocarbons released in this way are immediately passed on to the catalyst system 36 by the wake of the internal combustion engine.

The controller 50 also controls the throttle valve 24 in such a way that the throttle valve 24 remains closed even after the after-running of the internal combustion engine has ended, ie even when the engine is at a standstill. By this measure Prevents pollutants still present in the air intake pipe 18 from being able to evaporate into the environment through the inlet ducts 16, the combustion chambers 10, the outlet ducts 32, the catalyst system 36 and the exhaust system 38. It is also advantageous here if the throttle valve 24 is provided with suitable sealing elements for gas-tight closing.

Furthermore, the internal combustion engine of FIG. 1 is designed with one or more supply devices for secondary air (not shown). These can be provided in particular in the area of the inlet channels 16, the combustion chambers 10 and the outlet channels 32. The supply devices for secondary air are in no way limited to these locations, but can also be part of the exhaust gas recirculation system, for example.

The supply devices for secondary air are designed, for example, in the form of special inlet bores or inlet pipelines which are connected to corresponding components of the internal combustion engine and which can be opened and closed by means of suitable valve devices. The valve devices are preferably also controlled by the controller 50. Supply devices for secondary air in internal combustion engines are already known in principle for other purposes and can also be used in the internal combustion engine shown in FIG. 1. Examples of such feed devices are described in DE 196 42 685 AI and DE 198 32 627 AI. The feed devices are in no way limited to these two embodiments.

The operation of the internal combustion engine described above according to the method of the present invention will now be described with reference to the time diagrams of FIG. 2.

2a shows the time course of the engine speed in rpm. 2b is the time course of the position the throttle valve 24 shown; 2c shows the time course of the operating state of the ignition; 2d shows the time course of the operating state of the injection 22; 2e shows the time profile of the secondary air supply; and FIG. 2f shows the time course of the operating state of the starter system 14.

At a point in time ti, the motor vehicle driver wants to switch off the engine or the internal combustion engine, for example in order to switch off the motor vehicle. At this time ti, the controller 50 controls the internal combustion engine in such a way that the throttle valve 24 is closed starting from its normal load position (FIG. 2b), the injection is terminated as in conventional engines (FIG. 2d), and the starter system 14 is switched on ( Fig. 2f) and the secondary air supply is switched on (Fig. 2e). Due to the operation of the starter system 14, the engine speed only gradually decreases to a well-defined extent (FIG. 2a). The ignition initially remains switched on (Fig. 2c).

The defined after- _{running of} the internal combustion engine initiated in this way at time t _x lasts for a certain period of time Δt _ι2 = t ₂ -t _ι . After this period Δt _i2 , the secondary air supply (FIG. 2e) and the ignition (FIG. 2c) are switched off at time t ₂ . In contrast, the throttle valve 24 remains closed (FIG. 2b), the injection is switched off (FIG. 2d) and the starter system 14 is in operation (FIG. 2f). This state is maintained for a further period of time Δt ₂₃ = t ₃ -t ₂ . During this time period Δt ₂₃ , the internal combustion engine is braked to 0 rpm by the starter system 14 (FIG. 2a) and brought into the optimal starting position. As already described above, the throttle valve 24 preferably remains closed even after the overrun and the motor positioning have ended. The total time period Δt _i3 during which the starter system 14 is in operation is referred to as the first time period and the total time period Δt _X2 during which the secondary air supply is switched on is referred to as the second time period. As can be clearly seen in FIG. 2, the second time period Δt _{i2 of} the secondary air supply is preferably chosen to be shorter than the first time period Δt _{i3 of} the operation of the starter system 14.

Claims

DaimlerChrysler AG patent claims

Internal combustion engine, with a cylinder head (11), - a cylinder crankcase (12) connected to the cylinder head for receiving a crankshaft and at least one piston; at least one combustion chamber (10) delimited by the cylinder head, the cylinder crankcase and the respective piston; at least one inlet duct (16) connected to a combustion chamber (10) for supplying a fuel-air mixture; an air intake pipe (18) connected to the at least one inlet duct (16); at least one exhaust duct (32) connected to a combustion chamber (10) for removing exhaust gases; a starter system (14) coupled to the crankshaft arranged in the cylinder crankcase; and a controller (50) for controlling the internal combustion engine, characterized in that the controller (50) is designed such that, after a last combustion process (t _x ) in the at least one combustion chamber (10), it controls the starter system (14) for a specific first Period (Δt ₁₃ ) actuated.

Internal combustion engine according to claim 1, characterized in that the internal combustion engine further comprises at least one supply device for secondary air, the supply device for secondary air being coupled to a valve device.

3. Internal combustion engine according to claim 2, so that the motor control (50) controls the valve device of the secondary air supply device such that the internal combustion engine after a last one

Combustion process (ti) in which at least one combustion chamber (10) is supplied with secondary air for a specific second period (Δt ₁₂ ).

4. Internal combustion engine according to claim 2 or 3, characterized in that the secondary air at least one inlet duct (16), the at least one combustion chamber (11), the at least one outlet duct (32), an exhaust gas recirculation system and / or a catalyst system (36) of the internal combustion engine ^'is supplied.

5. Internal combustion engine according to claim 3 or 4, characterized in that the specific second period (Δt _i2 ) of the secondary air supply is shorter than the specific first period (Δt _i3 ) of the actuation of the starter system (14).

6. Internal combustion engine according to one of the preceding claims, characterized in that the controller (50) controls the starter system (14) such that the starter system during a specific third period (Δt ₂₃ ) at the end of the specific first period (Δtχ ₃ ) in the internal combustion engine sets an optimal starting state.

7. Internal combustion engine according to one of the preceding claims, characterized., Characterized, that a throttle valve (24) is provided in the air intake pipe (18) and the engine control (50) controls the throttle valve (24) such that the throttle valve is closed in a combustion chamber (10) after a last combustion process (t _x ).

8. Internal combustion engine according to claim 7, so that the throttle valve (24) is provided with sealing elements in such a way that the throttle valve can be closed essentially gas-tight.

9. Internal combustion engine according to claim 7 or 8, characterized in that the engine control (50) controls the throttle valve (24) such that the throttle valve remains closed even after the determined first period (Δt ₁₃ ).

10. Method for operating an internal combustion engine with a cylinder head (11); a cylinder crankcase (12) connected to the cylinder head for receiving a crankshaft and at least one piston; at least one combustion chamber (10) delimited by the cylinder head, the cylinder crankcase and the respective piston; at least one inlet duct connected to a combustion chamber (10)

(16) for supplying a fuel-air mixture; an air intake pipe (18) connected to the at least one inlet duct (16); at least one with a combustion chamber

(10) connected exhaust duct (32) for removing exhaust gases; a starter system (14) coupled to the crankshaft arranged in the cylinder crankcase; and a controller (50) for controlling the internal combustion engine, characterized in that, after a last combustion process (ti) in a combustion chamber (10), the starter system (14) is actuated for a specific first time period (Δt ₁₃ ).

11. The method according to claim 10, characterized in that the internal combustion engine after a last combustion process (t _x ) in a combustion chamber (10) for a certain second period (Δt _X2 ) is supplied with secondary air.

12. The method according to claim 11, characterized in that the secondary air is supplied to the at least one inlet duct (16), the at least one combustion chamber (11), the at least one outlet duct (32), an exhaust gas recirculation system and / or a catalyst system (36) of the internal combustion engine ,

13. The method according to claim 11 or 12, characterized in that the specific second period (Δt _i2 ) of the secondary air supply is shorter than the specific first period (Δt _i3 ) of the actuation of the starter system.

14. The method according to any one of claims 10 to 13, characterized in that the starter system (14) during a certain third period (Δt ₃ ) at the end of the specific first period (Δt ₁₃ ) sets the internal combustion engine in an optimal starting state.

15. The method according to any one of claims 10 to 14, characterized in that a throttle valve (24) in the air intake pipe (18) of the internal combustion engine is closed after a last combustion process (t _x ) in a combustion chamber (10).

16. ^' Method according to claim 15, characterized in that the throttle valve (24) is closed essentially gas-tight.

17. The method according to claim 15 or 16, dadurchgeke nn characterized in that the throttle valve (24) remains closed even after the determined first period (Δt _i3 ).