JP2005504916A - Method, computer program and control and / or regulating device for operating a direct injection internal combustion engine - Google Patents

Abstract

In internal combustion engines, fuel is discharged from at least one fuel pump into the high pressure region of the fuel system. From the high pressure region of the fuel system, the fuel directly reaches at least one combustion chamber of the internal combustion engine via at least one fuel injector. The fuel pressure (prist) in the high pressure region (20) of the fuel system depends on the current operating point (nmot, Md). In order to optimize the consumption characteristics and exhaust gas characteristics of the internal combustion engine, the fuel pressure (prist) in the high pressure region (20) of the fuel system is additionally determined by the operating modes (B1, B2, B3) in which the internal combustion engine is operated. ) Is also proposed to depend on.

Description

【Technical field】
[0001]
Prior Art The present invention first relates to the following method for operating a direct injection internal combustion engine. That is, a method of discharging fuel from at least one fuel pump to a high pressure region of a fuel system, and causing the fuel to reach at least one combustion chamber of the internal combustion engine via at least one fuel injection device from the high pressure region of the fuel system About. Here, the fuel pressure in the high pressure region of the fuel system depends on the current operating point of the internal combustion engine.
[0002]
This type of method is known from the market. Such a method is used in an internal combustion engine in which an electric fuel pump supplies fuel from a fuel tank to a second fuel pump. The second fuel pump is mechanically driven by the internal combustion engine. The second fuel pump discharges fuel to the fuel storage line (“rail”) under very high pressure, and the fuel is stored under high pressure in the fuel storage line. An injector is connected to the fuel storage line, and the injector directly injects fuel into the combustion chamber of the internal combustion engine.
[0003]
The pressure in the fuel storage line is detected by a pressure sensor, which sends a corresponding signal to the control device. The control device drives an amount control valve, and the amount of fuel discharged from the second fuel pump to the fuel accumulation line is adjusted by the amount control valve. In this manner, a closed loop control circuit for adjusting the pressure in the fuel storage line is configured. In the known method, a target value for the pressure in the fuel storage line is formed from the characteristic map. This characteristic map is addressed by the amount of operation representing the current operating point of the internal combustion engine. This amount of operation is, for example, the number of revolutions of the crankshaft of the internal combustion engine and the target torque of the internal combustion engine.
[0004]
The object of the present invention is to develop a method of the type described at the outset so that less fuel is consumed during operation of the internal combustion engine and the exhaust gas characteristics are better.
[0005]
Advantages of the invention The problem is solved by a method of the type described at the outset, in which the fuel pressure in the high pressure region of the fuel system is additionally dependent on the operating mode operated in the internal combustion engine. Is done.
[0006]
In the present invention, the fuel pressure in the high pressure region of the fuel system is an operation amount that affects the combustion characteristics of the fuel in the combustion chamber differently when the operation mode of the internal combustion engine is different, such as the ignition angle and the injection time point. It has been confirmed. The concept of “operation mode” refers to different methods of operating a direct injection internal combustion engine. Examples of such operation modes include uniform operation, stratified operation, uniform / stratified operation, operation with exhaust gas recirculation, operation without exhaust gas recirculation, and uniform lean operation.
[0007]
In addition, the uniform operation refers to an operation in which when fuel reaches the combustion chamber of the internal combustion engine, the fuel is substantially uniformly distributed at the time of ignition in the combustion chamber. This is especially true for injections during the intake stroke. On the other hand, during stratified operation of the internal combustion engine, there is an air-fuel mixture that can be ignited only in the region of the spark plug in the combustion chamber, and there is little or no fuel in the remaining portion of the combustion chamber. During stratification, injection is also performed during the compression stroke. Stratified operation is advantageously carried out when the load is small and the engine is partly loaded.
[0008]
Considering these different operating modes when detecting the fuel pressure in the high pressure region of the fuel system, the optimal fuel pressure is obtained for each operating mode, and therefore the combustion conditions of the fuel in the combustion chamber are optimal become. This improves the consumption characteristics and exhaust gas characteristics of the internal combustion engine.
[0009]
Advantageous developments of the invention are described in the dependent claims.
[0010]
Here, for example, the target value for the fuel pressure in the high pressure region of the fuel system is at least occasionally determined by a characteristic map specific to each type of operation, and this characteristic map is addressed by a characteristic quantity at the current operating point. Has been proposed. In this development of the method according to the invention, a corresponding characteristic map is provided for each operating mode, which determines a target value for the fuel pressure in the high pressure region of the fuel system. Such a method for determining the target value for fuel pressure is very accurate and can be easily implemented by software technology.
[0011]
The quantity characteristic of the operating point is particularly advantageous when it includes the rotational speed of the crankshaft of the internal combustion engine and the target torque of the internal combustion engine. In any case, since these are generally existing, it is not necessary to provide an additional sensor in order to detect the current operating point.
[0012]
Furthermore, when the first operation mode is shifted to the second operation mode, the target value of the fuel pressure in the high pressure region of the fuel system is still detected based on the first operation mode over a predetermined time. Proposed. This is based on the consideration that the target value setting should be avoided from changing suddenly when switching from one operation mode to another operation mode.
[0013]
This means that the fuel pressure in the high pressure region of the fuel system changes suddenly during the process of switching from one operation mode to another, thereby generating an undefined fuel pressure in the high pressure region. It is related to having sex. Such undefined fuel pressures may in some cases not meet the other parameters of the new operating mode, and even for a short time, the operation of the internal combustion engine may be disturbed, for example combustion There is a possibility of misfire. This is avoided by this development of the method according to the invention.
[0014]
In addition, when shifting from the first operation mode to the second operation mode, the target value of the fuel pressure in the high pressure region of the fuel system can be kept constant over a predetermined time. Such “freezing” of the target value can be easily realized.
[0015]
Here, it is also advantageous to obtain the target value of the fuel pressure in the high pressure region of the fuel system based on the first operation mode until the second operation mode is stabilized. This is generally the case after several combustions, for example after the internal combustion engine has burned about 10 times or after about 10 operating cycles.
[0016]
In an advantageous configuration of the method according to the invention, it has also been proposed to set the target value of the fuel pressure in the high pressure region of the fuel system to a value corresponding to the new operating mode via a ramp or filter. This also avoids a sudden change in the target value setting for the fuel pressure in the high pressure region of the fuel system. This can lead to a sudden change in the combustion of the fuel in the combustion chamber of the internal combustion engine and a corresponding reduction in comfort for the user.
[0017]
Particularly advantageously, the value of the fuel pressure in the high-pressure region of the fuel system corresponding to the new operating mode is already detected during the process of switching from the first operating mode to the second operating mode. In this way, the corresponding value can be obtained immediately and stably and the adaptation of the fuel pressure to the new operating mode is carried out quickly.
[0018]
The invention also relates to a computer program suitable for carrying out the method when the method is carried out on a computer. Here, it is particularly advantageous to store the computer program in a memory. Said memory is in particular a flash memory or a ferrite RAM.
[0019]
The invention further relates to a control and / or regulating device for operating an internal combustion engine. In order to allow the internal combustion engine to operate optimally in terms of consumption and exhaust gas, the control and / or regulating device has a memory, and is configured such that a computer program of the above type is stored in the memory. It has been proposed.
[0020]
In the following, particularly advantageous embodiments of the invention will be described in detail in connection with the accompanying drawings.
[0021]
FIG. 1 is a basic diagram of the configuration of an internal combustion engine provided with a fuel system having a high pressure region.
[0022]
FIG. 2 is a flowchart illustrating a method for setting a target value of fuel pressure in a high pressure region of the fuel system illustrated in FIG. 1 depending on an operation mode.
[0023]
3 is a graph in which the operation mode switching state of the internal combustion engine of FIG. 1 is plotted over time.
[0024]
4 is a graph in which the target fuel pressure in the high pressure region of the fuel system of the internal combustion engine shown in FIG. 1 is plotted over time.
[0025]
DESCRIPTION OF THE EMBODIMENTS In FIG. 1, the internal combustion engine generally has the reference numeral 10. The internal combustion engine has a fuel system 12. In particular, a fuel tank 14 belongs to the fuel system 12. From this fuel tank 14, the electric fuel pump 16 discharges fuel to the high-pressure fuel pump 18 via the low-pressure fuel line 17. From here, the fuel reaches the fuel storage line 20 ("rail") under high pressure. A plurality of injectors 22 are connected to the fuel storage line 20. These injectors 22 inject fuel directly into the combustion chamber 24.
[0026]
The amount of fuel discharged from the high-pressure fuel pump 18 to the fuel accumulation line 20 is adjusted by the amount control valve 26. When the quantity control valve 26 is in an open state, the working space (not shown) of the high-pressure fuel pump 18 and the low-pressure fuel line 17 are connected. When the quantity control valve 26 is opened during the discharge stroke of the high pressure fuel pump 18, the fuel is not discharged into the fuel storage line 20 but is discharged back into the low pressure fuel line 17. The amount of fuel discharged to the fuel storage line 20 is adjusted according to the time during which the amount control valve 26 is opened during the discharge stroke of the high-pressure fuel pump 18, and the fuel pressure existing in the fuel storage line 20 is adjusted accordingly. Is done. In this way, the fuel accumulation line 20, the pressure sensor 28, the control adjustment device 30 and the amount control valve 26 constitute a closed loop control circuit.
[0027]
The fuel pressure in the fuel storage line 20 of the fuel system 12 is detected by a pressure sensor 28. The pressure sensor 28 supplies a corresponding signal to the control adjustment device 30. The internal combustion engine 10 also includes an accelerator pedal 32, and the position of the accelerator pedal 32 is detected by a position sensor 34. This position sensor 34 is also connected to the control adjustment device 30. The rotational speed of the crankshaft (not shown) of the internal combustion engine 10 is detected by a rotational speed sensor 36, which likewise transmits a corresponding signal to the control adjustment device 30.
[0028]
The internal combustion engine 10 is operated in different operation modes. For example, when the rotational speed is low and / or when the target torque is low, the internal combustion engine 10 operates in the operation mode “stratification”. At that time, when the fuel is injected into the combustion chamber 24 by the injector 22, the fuel is stratified in the combustion chamber 24. This means that there is a fuel mixture that can be ignited substantially only in the region of the spark plug (not shown). On the other hand, in the operation mode “uniform”, when fuel is injected, the fuel is uniformly distributed throughout the combustion chamber 24.
[0029]
It is also conceivable that the operating point is different for each operation mode. These operating points are defined by, for example, the rotational speed of the crankshaft of the internal combustion engine 10 and the target torque. In the internal combustion engine 10 shown in FIG. 1, the target value of the fuel pressure in the fuel accumulation line 20 depends on the operation mode and the operation point of the internal combustion engine 10. This will now be described in more detail based on the method shown in FIG.
[0030]
In the method shown in FIG. 2, it is assumed as an example that the internal combustion engine 10 is operated in three different operating modes B1, B2 and B3. The characteristic maps KF1, KF2, and KF3 are stored in the memory of the control adjustment device 30 for each operation mode. The characteristic maps KF1 to KF3 are addressed by the rotational speed nmot detected by the rotational speed sensor 36 and the target torque Md obtained from the position wped of the accelerator pedal 32.
[0031]
In this embodiment, it is first assumed that the internal combustion engine 10 is operating in the operation mode B1 (see FIG. 3). At time t1, it is determined by control that there is an appropriate condition for switching to operation mode B2. This control is not described in detail here. Therefore, the operation mode is switched to B2. This includes, for example, ignition point shift, injection point shift, valve opening for exhaust gas recirculation, throttle valve position change, and the like.
[0032]
By starting the switching from the operation mode B1 to the operation mode B2, the delay element is started in the block 50. Thus, the characteristic map KF1 is switched to the characteristic map KF2 only after the waiting time T1 has elapsed in the switching block 52. Therefore, until the time T1 elapses, the target value prsoll KF1 formed by the characteristic map KF1 continues to be used as the target value prsoll for the fuel pressure in the fuel storage line 20 of the fuel system 12.
[0033]
Only after the elapse of time T1 is the block 52 switched to the characteristic map KF2 corresponding to the new operating mode B2. Thereafter, the target value prsollKF2 formed by the characteristic map KF2 is transmitted from the switching block 52 to the filter 54. In the filter 54, the target value prsoll is adapted via a ramp from the value prsollKF2 formed with the previous characteristic map KF1 to the value prsollKF2 formed with the new characteristic map KF2. By doing so, a rapid change in the target fuel pressure prsoll is prevented (see FIG. 4). The duration of the lamp obtained by the filter 54 is indicated by T2 in FIG.
[0034]
A target value prsoll for the fuel pressure is supplied to the control device 56. The controller 56 is also supplied with the instantaneous value prist of the fuel pressure detected by the pressure sensor 28. A corresponding signal is generated in the control device 46, and the amount control valve 26 is driven by this signal.
[0035]
In an embodiment not shown here, the previous characteristic map is not used for a predetermined time after the start of the switching process from one operating mode to another, but instead the high pressure region of the fuel system. The target value of the fuel pressure is maintained for a predetermined time.
[Brief description of the drawings]
[0036]
FIG. 1 is a basic diagram of a configuration of an internal combustion engine provided with a fuel system having a high pressure region.
[0037]
2 is a flowchart illustrating a method for setting a target value of a fuel pressure in a high pressure region of the fuel system illustrated in FIG. 1 depending on an operation mode.
[0038]
FIG. 3 is a graph in which the operating mode switching state of the internal combustion engine of FIG. 1 is plotted over time.
[0039]
4 is a graph in which the target fuel pressure in the high pressure region of the fuel system of the internal combustion engine shown in FIG. 1 is plotted over time.

Claims (11)

A method for operating a direct injection internal combustion engine (10) comprising:
Discharging fuel from at least one fuel pump (18) into the high pressure region (20) of the fuel system (12);
The fuel directly reaches the at least one combustion chamber (24) of the internal combustion engine (10) from the high pressure region (20) of the fuel system (12) via at least one fuel injector (22). ,
In a method of the type in which the fuel pressure (prist) in the high pressure region (20) of the fuel system (12) depends on the current operating point (nmot, Md) of the internal combustion engine (10),
The fuel pressure (prist) in the high pressure region (20) of the fuel system (12) additionally depends on the operation mode (B1, B2, B3) in which the internal combustion engine (10) is operated. how to. A target value (prsoll) for the fuel pressure in the high pressure region (20) of the fuel system (12) is determined at least occasionally by a characteristic map (KF1, KF2, KF3) specific to each operation mode (B1, B2, B3). ,
The method according to claim 1, wherein the characteristic map is addressed by a quantity (nmot, Md) characteristic of the current operating point. The method according to claim 2, wherein the quantities specific to the operating point include the crankshaft speed (nmot) of the internal combustion engine (10) and the target torque (Md) of the internal combustion engine (10). When shifting from the first operation mode (B1) to the second operation mode (B2), the target value of the fuel pressure in the high pressure region (20) of the fuel system (12) is still set over a predetermined time (T1). The method according to claim 1, wherein the method is determined based on the first operation mode (B1) (KF1). The target value of the fuel pressure in the high pressure region of the fuel system is maintained constant over a predetermined time when shifting from the first operation mode to the second operation mode. The method described. Until the second operation mode (B2) is stabilized, a target value (prsoll) of the fuel pressure in the high pressure region (20) of the fuel system (12) is obtained based on the first operation mode (B1). 6. The method of claim 4 or 5, wherein (KF1) or is kept constant. The target value (prsoll) of the fuel pressure in the high pressure region (20) of the fuel system (12) is set to a value (prsollKF2) corresponding to the new operation mode (B2) via a lamp or filter (54). The method according to claim 5 or 6. Already during the process of switching from the first operating mode (B1) to the second operating mode (B2), in the high pressure region (20) of the fuel system (12) corresponding to the second operating region (B2). The method according to claim 5, wherein the fuel pressure is determined (KF2). In a computer program,
9. A computer program characterized in that when the method according to claim 1 is carried out on a computer, the method is suitable for carrying out the method. Stored in memory,
The computer program according to claim 9, wherein the memory is, for example, a flash memory or a ferrite RAM. In a control and / or regulating device (30) for operating an internal combustion engine,
Memory is included,
A control and / or adjustment device (30), characterized in that the computer program according to claim 9 or 10 is stored in the memory.