DE10148651C1 - Automobile internal combustion engine operating method with switching between two operating modes for fuel injection during compression phase or suction phase - Google Patents

Abstract

The engine operating method has the fuel injected into the engine during the compression phase in one engine operating mode and during the suction phase in a second engine operating mode, with switching between the operating modes during running of the engine and recycling of the engine exhaust gas for mixing with the air-fuel mixture. The beginning of the fuel injection during the second operating mode is determined in dependence on the exhaust gas feedback rate (AGR) and the fuel injection pressure (pr). Independent claims are also included for: a microprocessor computer program for operation of the IC engine; a control device for the IC engine; and an IC engine.

Description

State of the art

The present invention relates to a method for Operating an internal combustion engine, in particular one Motor vehicle. This is fuel in a first Operating mode during a compression phase and in one second operating mode during an intake phase into one Combustion chamber of the internal combustion engine injected. During the Operation of the internal combustion engine is between the Operating modes switched. In addition, the fuel injected with a variable injection pressure and the Fuel injection at a variable time began. Eventually, burned exhaust gas becomes one Fuel-air mixture returned.

The invention also relates to a computer program that on a computing device, in particular on a Microprocessor that is executable.

The present invention further relates to a Control device for an internal combustion engine, in particular one Motor vehicle. The internal combustion engine has one Direct fuel injection and exhaust gas recirculation and can be operated in different operating modes. In a first mode is fuel during a  Compression phase and in a second mode of operation during an intake phase in a combustion chamber of the internal combustion engine can be injected with a variable injection pressure. The Control unit determines the start of injection of the Fuel injection.

Finally, the invention also relates to a Internal combustion engine, in particular of a motor vehicle. The Internal combustion engine has a combustion chamber Fuel metering system, a control unit and one Exhaust gas recirculation. The fuel metering system is spraying Fuel into the combustion chamber in a first operating mode during one compression phase and in a second Operating mode during a suction phase with a variable Injection pressure and a variable start of injection. The Control unit is used to switch between the Operating modes, for setting the injection pressure and Determine the start of injection during the operation of the Internal combustion engine. The exhaust gas recirculation leads Combustion gases from an exhaust pipe into an intake pipe the internal combustion engine, through which it in turn in the Reach the combustion chamber and find a fuel-air Mix the mixture with fuel.

An internal combustion engine is known from EP 0 893 593 A2 known type. In this publication described that when switching on the exhaust gas recirculation the internal combustion engine may run rough. For this reason, the publication proposes the air-fuel ratio, the start of injection and the Correct ignition timing. This is said to be a quieter one Running the internal combustion engine, especially when switching on exhaust gas recirculation.  

From DE 199 08 726 A1 it is known that Start of injection depending on smooth running of the Vary internal combustion engine. This is supposed to be as possible fuel-saving and low-emission operation of the Internal combustion engine are made possible without this other engine-related boundary conditions are replaced.

Internal combustion engines with exhaust gas recirculation are part of the stand of the technique. With exhaust gas recirculation Combustion gases from an exhaust pipe back into one Intake pipe led. From there they get into the Combustion chamber of the internal combustion engine and mix there with injected fuel to a fuel-air Mixture. When operating the internal combustion engine with deactivated exhaust gas recirculation becomes ambient air with a Temperature between -15 ° C and + 30 ° C sucked in. The Combustion gases have a relatively high temperature in the Range of about 200 ° C to 400 ° C, so that the Operation of the internal combustion engine with activated Exhaust gas recirculation new engine-related conditions result, which must be taken into account.

An important target of internal combustion engines for Motor vehicle is one as low as possible Fuel consumption at the lowest possible Exhaust emissions. For this it is necessary that everyone possible operating modes (e.g. shift operation, Homogeneous operation with and without exhaust gas recirculation, Homogeneous lean operation with and without exhaust gas recirculation, etc.) for data records or map data that are as comprehensive as possible can access so that the setting parameters of the The combustion-determining parameters optimally set can be. A particularly large fuel The homogeneous operation with large offers savings potential Exhaust gas recirculation rates. In this mode, after State of the art no separate map is provided. Out  For this reason, the parameters "start of injection" from the Homogeneous operation without exhaust gas recirculation and "injection pressure" taken from the shift operation. This inevitably poses a compromise solution.

If an internal combustion engine in homogeneous operation without Exhaust gas recirculation is operated and the exhaust gas recirculation then switched on, the temperature rises above that Intake pipe strongly sucked in air. These high Intake air temperatures are used for the secondary Mixture processing exploited. With the secondary Mixture preparation becomes the evaporation properties of fuel on the warmed walls of the Combustion chambers and the piston of the internal combustion engine exploited. This is particularly possible if the Fuel over as long an injection period as possible Combustion chambers is injected. To that in a constant Operating point in the context of an injection process keeping the injected fuel mass constant is at an extended period of time per unit of time injected fuel mass reduced. As a result, that a lower fuel mass per unit of time on the Hits walls and at least partially evaporates there, without cooling the walls too much.

At the same time, the fuel injection system or in a high pressure area of the fuel injection system prevailing injection pressure can be reduced to the pro Unit of time injected into the combustion chamber to reduce. At the same time, the injection must start be moved to "early" so that the Fuel injection has ended in time for one optimal mixture preparation before ignition initiation guarantee.

According to the state of the art, exhaust gas recirculation cannot  be used to improve the mixture preparation, since it is not yet possible to use the various parameters to coordinate accordingly without the course of the To affect the internal combustion engine.

The present invention is based on the object Exhaust gas recirculation for an improvement in Mixture preparation in the combustion chamber and thus for one Saving fuel and reducing exhaust and Exploiting noise emissions from the internal combustion engine.

To achieve this object, the invention is based on of the method of the type mentioned above that the Depending on the start of injection in the second operating mode on the exhaust gas recirculation rate and depending on that Injection pressure is determined.

Advantages of the invention

There are different types of mixture preparation known. A so-called primary mixture preparation is especially by shaping and aligning a Fuel injection jet influenced in the combustion chamber. This mainly causes turbulence in the Combustion chamber a mixture of fuel and air. A so-called secondary mixture preparation, however, is from Evaporation properties of the fuel on the wall a combustion chamber or a piston of the internal combustion engine affected. In the present invention, the Mixture preparation especially in the secondary area Mixture preparation improved.

With the method according to the invention, one particular good mixture preparation and thus the Fuel consumption, exhaust and noise emissions be reduced. This is particularly because of this  enables the start of injection depending on the Exhaust gas recirculation rate and injection pressure vary can be and the injectors accordingly can be controlled.

According to an advantageous development of the present Invention is proposed that depending on the Injection pressure a first correction value and depending a second correction value from the exhaust gas recirculation rate is determined and a regardless of the exhaust Return rate and / or independent of the injection pressure determined value for the start of injection by means of Correction values is corrected.

It is suggested that the first correction value and the second correction value based on a characteristic curve or Map are determined.

According to a preferred embodiment of the present Invention it is proposed that the correction values increase regardless of the exhaust gas recirculation rate and / or irrespective of the value for determined by the injection pressure the start of injection can be added.

As a further solution to the problem of the present Invention is based on the computer program of the initially suggested that the Computer program for executing the invention Procedure is appropriate when it is on the computing device expires. In this case, the invention is Computer program realized that in the same way Invention represents how the method for carrying it out the computer program is suitable.

According to an advantageous development of the present Invention it is proposed that the computer program  a memory element, in particular on a random Access memory, a read-only memory or a flash Memory that is saved.

As yet another solution to the problem of the present Invention is based on the control unit for a Internal combustion engine of the type mentioned suggested that the controller start injection at the second operating mode depending on the exhaust gas Feedback rate and depending on the injection pressure determined.

According to an advantageous development of the present Invention it is proposed that the control device means for carrying out the method according to the invention.

Finally, the task is solved yet another of the present invention based on the Internal combustion engine of the type mentioned suggested that the start of injection in the second Operating mode depending on the exhaust gas recirculation rate and can be determined as a function of the injection pressure.

According to an advantageous development of the present Invention, it is proposed that the internal combustion engine Means for performing the method according to the invention having.

drawings

Other features, applications and advantages of Invention result from the following description of embodiments of the invention, which in the Drawing are shown. Thereby form all described or illustrated features for themselves or in any Combination the subject of the invention, regardless of  their summary in the claims or their Relationship and regardless of their wording or Representation in the description or in the drawing. It demonstrate:

Fig. 1, an internal combustion engine according to the invention in a preferred embodiment with a control device and a fuel metering system for a direct fuel injection; and

Fig. 2 shows a structure grams of an inventive method according to a preferred embodiment.

Description of the embodiments

In Fig. 1, an internal combustion engine is designated in its entirety with reference number 1 . The internal combustion engine 1 comprises one or more cylinders 3 , of which only one is shown as an example in FIG. 1. A piston 2 can be moved back and forth in the cylinder 3 . The cylinder 3 is provided with a combustion chamber 4 which is delimited inter alia by the piston 2 , an inlet valve 5 and an outlet valve 6 . An intake pipe 7 is coupled to the inlet valve 5 and an exhaust pipe 8 is coupled to the outlet valve 6 .

In the area of the intake valve 5 and the exhaust valve 6, an injection valve 9 and a spark plug 10 protrude into the combustion chamber 4 . Fuel can be injected directly from a fuel metering system 21 into the combustion chamber 4 via the injection valve 9 . The fuel in the combustion chamber 4 can be ignited with the spark plug 10 .

The fuel metering system 21 is designed as a high-pressure accumulator fuel injection system. It includes a pre-feed pump 22 which conveys fuel from a fuel reservoir 23 into a low pressure area ND of the fuel metering system 21 . The prefeed pump 22 is designed, for example, as an electric fuel pump (EKP). Fuel is conveyed from the low pressure region ND by a high pressure pump 24 into a high pressure region HD. The high-pressure pump 24 is designed, for example, as a single-cylinder piston pump or as a three-cylinder radial piston pump. The fuel delivered by the high pressure pump 24 is present with a relatively high injection pressure pr in the high pressure area HD. A storage rail 25 (common rail) is arranged in the high-pressure area HD, in which fuel is stored at the injection pressure pr. Connecting lines 26 branch off from the memory strip 25 and lead to the injection valves 9 in the various cylinders 3 of the internal combustion engine 1 . A pressure sensor 27 is arranged in the memory strip 25 , which detects the injection pressure p _r prevailing in the high-pressure region HD and outputs a corresponding electrical signal.

In the intake pipe 7 , a rotatable throttle valve 11 is accommodated, via which air can be supplied to the intake pipe 7 . The amount of air supplied is dependent on the angular position of the throttle valve 11 . A catalytic converter 12 is accommodated in the exhaust pipe 8 and serves to clean the exhaust gases resulting from the combustion of the fuel.

An exhaust gas recirculation pipe 13 leads from the exhaust pipe 8 back to the intake pipe 7 . An exhaust gas recirculation valve 14 is accommodated in the exhaust gas recirculation pipe 13 , with which the amount of the exhaust gas recirculated into the exhaust gas pipe 7 can be adjusted. The exhaust gas recirculation pipe 13 and the exhaust gas recirculation valve 14 form a so-called exhaust gas recirculation.

The combustion of the fuel in the combustion chamber 4 causes the piston 2 to move back and forth, which is transmitted to a crankshaft (not shown) and exerts a torque thereon.

A control unit 18 is acted upon by input signals 19 , which represent operating variables of the internal combustion engine 1 measured by sensors. For example. the control unit 18 is connected to an air mass sensor, a lambda sensor, a speed sensor, a temperature sensor, the pressure sensor 27 and the like. The control unit 18 generates output signals 20 with which the behavior of the internal combustion engine 1 can be influenced via actuators or actuators. For example. is the control unit 18 to the fuel injector 9 (control signal for start of injection in homogeneous operation t _ESBH), the spark plug 10 (trigger signal for ignition time T _ignition and the throttle valve connected 11 and the like and generates the required for driving the drive signals. Among other things, the control unit 18 is to provided to control and / or regulate the operating variables of the internal combustion engine 1. For example, the fuel mass injected into the combustion chamber 4 by the injection valve 9 is controlled and / or controlled by the control unit 18, in particular with regard to low fuel consumption and / or low pollutant emissions For this purpose, the control unit 18 is provided with a microprocessor 28 , which has stored a computer program in a storage medium 29 , in particular in a flash memory, which is suitable for carrying out the control and / or regulation mentioned Computer program through the Rechenge advises 28 , the computer program is transmitted either as a whole or by command from the storage medium 29 to the computing device 28 via a communication link 30 .

The internal combustion engine 1 from FIG. 1 can be operated in a large number of operating modes. It is thus possible to operate the internal combustion engine 1 in a stratified operation, a homogeneous operation with or without exhaust gas recirculation, a homogeneous lean operation with and without exhaust gas recirculation and the like. In homogeneous operation, the fuel is injected from the injection valve 9 directly into the combustion chamber 4 of the internal combustion engine 1 during the intake phase. As a result, the fuel is largely swirled up to the point of ignition, so that an essentially homogeneous fuel-air mixture is produced in the combustion chamber 4 . The torque to be generated is essentially set by the control unit 18 via the position of the throttle valve 11 . In homogeneous operation, the operating variables of internal combustion engine 1 are controlled and / or regulated in such a way that a fuel-air ratio (lambda) is set to 1. Homogeneous operation is used particularly at full load.

The homogeneous lean operation largely corresponds to that Homogeneous operation, however, the lambda becomes one value set greater than 1.

In stratified operation, the fuel is injected from the injection valve 9 directly into the combustion chamber 4 of the internal combustion engine 1 during the compression phase. Thus, when the spark plug 10 is ignited, there is no homogeneous mixture in the combustion chamber 4 , but rather a fuel stratification. The throttle valve 11 can, apart from requirements such. B. the exhaust gas recirculation and / or a tank ventilation completely open and the engine 1 can be operated dethrottled. The torque to be generated is largely set via the fuel mass in shift operation. With the stratified operation, the internal combustion engine 1 can be operated in particular at idle and at partial load.

It is possible to switch between the aforementioned operating modes of the internal combustion engine 1 . Such switching operations are carried out by the control unit 18 .

The goal of direct-injection internal combustion engines is the lowest possible fuel consumption with the lowest possible exhaust gas emissions. For this it is necessary to provide the best possible and complete data for all possible operating modes so that the setting parameters of the variables determining the combustion process can be set optimally. Homogeneous operation with high exhaust gas recirculation rates offers great potential for saving fuel. In order to improve the mixture preparation in this operating mode, it is proposed _according to the invention that the control unit 18 determines the start of injection t _ESBH as a function of the exhaust gas recirculation rate EGR and as a function of the injection _pressure p _r . The injection valves 9 are then controlled with the determined value for the start of injection t _ESBH .

In Fig. 2 is a structure chart of the inventive method is illustrated. A speed of the internal combustion engine 1 n _mot , a relative load rl, a temperature T _{mot of} the internal combustion engine 1 and a threshold value T _mots for the engine temperature are applied to the control unit 18 as input variables. The engine speed n _mot can be determined by means of a speed sensor. The relative load is characterized, for example, by the air mass sucked in or the torque delivered. The engine temperature Tmot can be determined, for example, via the temperature of a cooling water or an oil circuit of the internal combustion engine 1 . The threshold value T _mots can be specified as desired. In addition, the injection pressure p _r prevailing in the high-pressure region HD of the fuel metering system 21 and an exhaust gas recirculation rate EGR are present at the control unit 18 . The injection pressure p _r can be measured by means of the pressure sensor 27 . The exhaust gas recirculation rate EGR can be determined, for example, on the basis of the position of the exhaust gas recirculation valve 14 or on the basis of a control signal AGR for the exhaust gas recirculation valve 14 .

The engine speed n _mot and the relative load rl are supplied to a first map K1 and a second map K2 for determining a first value k1 and a second value k2. The engine temperature T _mot is fed to a two-dimensional map (characteristic curve K3) in order to determine a third value k3. A comparator V checks whether the current engine temperature T _{mot is} greater than the predefinable threshold value T _mots . Depending on the result of the comparison, a switching element S is _activated , which switches between the corrected start of injection T _ESBH and the first value k1. If the engine temperature T _mot exceeds the threshold value T _mots , the switching element S switches and the first value k1 is output.

A value t ^* _ESBH for the start of injection determined independently of the exhaust gas recirculation rate EGR and independently of the injection _pressure p _r has the equation:

t ^* _ESBH = (k1 - k2) .k3 + k2.

This value t ^* _ESBH is corrected using the method according to the invention.

The injection pressure p _r is a two-dimensional map (characteristic) K4 for determining a first correction value p _r _korr and the exhaust gas recirculation rate EGR is also supplied to a two-dimensional map (characteristic) K5 for determining a second correction value AGR_korr. The two correction values p _r _korr and EGR_korr are added to the value t ^* _ESBH determined independently of the injection pressure p _r and / or independently of the exhaust gas recirculation rate AGR. The start of injection t _ESBH thus results from the equation:

t _ESBH = (k1 - k2) k3 + k2 + p _r _korr + AGR_korr.

With the aid of the method according to the invention, in particular the secondary mixture preparation can be improved, since the intake air has a significantly higher temperature than without exhaust gas recirculation due to the exhaust gas recirculation. These high temperatures heat up the walls of the combustion chamber 3 or the piston 2 in such a way that fuel injected via the injection valve 9 evaporates much better at the walls and is distributed over the combustion chamber 3 . To improve the secondary mixture preparation, the injection period is extended p _r reduced within a constant operating point, the injection pressure and injection timing t _ESBH to move "early", so that the fuel injection is completed in good time prior to ignition to ensure optimum mixture preparation before ignition initiation. The "Start of injection" parameter can therefore be optimally set in homogeneous operation with exhaust gas recirculation.

Claims (11)

1. Method for operating an internal combustion engine ( 1 ), in particular a motor vehicle, in which fuel is injected into a combustion chamber ( 4 ) of the internal combustion engine ( 1 ) in a first operating mode during a compression phase and in a second operating mode during which Operation of the internal combustion engine ( 1 ) is switched between the operating modes in which the fuel is injected at a variable injection pressure (pr), at which the fuel injection is started at a variable point in time (t_ESBH) and in the case of the burned exhaust gas to a fuel-air Mixture is returned, characterized in that the start of injection (t_ESBH) in the second operating mode is determined as a function of the exhaust gas recirculation rate (EGR) and as a function of the injection pressure (pr). 2. The method according to claim 1, characterized in that a first correction value (pr_korr) is determined as a function of the injection pressure (pr) and a second correction value (AGR_korr) is determined as a function of the exhaust gas recirculation rate (AGR) and one is independent of the exhaust gas - The feedback rate (EGR) and / or the value determined independently of the injection pressure (pr) (t ^* _ESBH) for the start of injection is corrected by means of the correction values (pr_korr, AGR_korr). 3. The method according to claim 2, characterized in that the first correction value (pr_korr) based on a Characteristic curve or map (K4) is determined. 4. The method according to claim 2 or 3, characterized characterized that the second correction value (AGR_korr) determined on the basis of a characteristic curve or a characteristic diagram (K5) becomes. 5. The method according to any one of claims 2 to 4, characterized in that the correction values (AGR_korr, pr_korr) to the value (t ^* _ESBH) determined independently of the exhaust gas recirculation rate (EGR) and / or independently of the injection pressure (pr) be added for the start of injection. 6. Computer program that can run on a computing device ( 28 ), in particular on a microprocessor, characterized in that the computer program is suitable for executing a method according to one of claims 1 to 5 when it runs on the computing device ( 28 ). 7. Computer program according to claim 6, characterized in that the computer program is stored on a memory element ( 29 ), in particular on a random access memory, a read-only memory or a flash memory. 8. Control unit ( 18 ) for an internal combustion engine ( 1 ), in particular of a motor vehicle, the internal combustion engine ( 1 ) having direct fuel injection and exhaust gas recirculation and being operable in different operating modes, being in a first operating mode during a compression phase and in a second Operating mode during an intake phase, fuel can be injected into a combustion chamber ( 4 ) of the internal combustion engine ( 1 ) with a variable injection pressure (pr), and the control unit ( 18 ) determines the start of injection (t_ESBH) of the fuel injection, characterized in that the control unit ( 18 ) the start of injection (t_ESBH) in the second operating mode as a function of the exhaust gas recirculation rate (EGR) and as a function of the injection pressure (pr). 9. Control device ( 18 ) according to claim 8, characterized in that the control device ( 18 ) has means for performing a method according to one of claims 2 to 5. 10. Internal combustion engine ( 1 ), in particular of a motor vehicle, with a combustion chamber ( 4 ), with a fuel metering system ( 21 ) for injecting fuel into the combustion chamber ( 4 ) in a first operating mode during a compression phase and in a second operating mode during an intake phase with a variable injection pressure (pr), a variable injection start (t_ESBH) and a variable injection duration, with a control unit ( 18 ) for switching between the operating modes, for setting the injection pressure (pr) and for determining the injection start (t_ESBH) and the injection duration during operation the internal combustion engine ( 1 ) and with an exhaust gas recirculation to a fuel-air mixture, characterized in that the start of injection (t_ESBH) can be determined in the second operating mode as a function of the exhaust gas recirculation rate (EGR) and as a function of the injection pressure (pr) is. 11. Internal combustion engine ( 1 ) according to claim 10, characterized in that the internal combustion engine ( 1 ) has means for carrying out a method according to one of claims 2 to 5.