JP2005504912A - Method for operating an internal combustion engine, computer program, open loop and / or closed loop control device, and internal combustion engine - Google Patents

Abstract

In this method for operating an internal combustion engine, fuel is directly injected into at least one combustion chamber via at least one fuel injection device. The valve element of the fuel injection device is movable by a piezo actuator. Furthermore, the torque generated under the combustion of the amount of fuel injected into the combustion chamber during injection is determined. In the present invention, in order to optimize the fuel consumption characteristics and exhaust gas characteristics of the internal combustion engine, the current valve characteristic curve (fc) of the fuel injection device incorporated in the internal combustion engine is at least approximately determined from the torque. In this case, the valve characteristic curve (fc) combines the fuel mass flow rate (Qstat) to be delivered from the fuel injector and the drive control energy to be supplied to the piezo actuator.

Description

【Technical field】
[0001]
In the present invention, first, fuel is directly injected into at least one combustion chamber via at least one fuel injection device, and the valve element of the fuel injection device is movable by a piezo actuator, and is injected into the combustion chamber at the time of injection. The invention relates to a method for operating an internal combustion engine, in which a torque generated under the combustion of a given amount of fuel is determined.
[Background]
[0002]
Such methods are also known in the market. Under this method, fuel is first supplied to a high-pressure fuel pipe (“common rail”) and stored therein under high pressure. A plurality of injectors are connected to the fuel pipe, and the fuel is directly injected into the corresponding combustion chamber of the internal combustion engine by these injectors. This injection can be performed so that the ignitable fuel-air mixture is concentrated only in the region around the spark plug. In contrast, there is very little or no fuel in the other combustion chambers ("stratified intake mode"). In this mode of operation, the intake air into the combustion chamber is substantially completely opened, and the torque is substantially determined solely by the amount of fuel injected from the injector into the combustion chamber.
[0003]
In order to be able to guarantee the best possible intake and to optimize the exhaust characteristics of the internal combustion engine, so-called “cylinder balance adjustment” is performed in the known method. At that time, the torque generated in each combustion chamber under specific combustion within one operation stroke (for two rotations of the crankshaft) is determined for each cylinder of the internal combustion engine. The injector opening time is changed so that the torque difference between the individual cylinders is minimized. In this way, the manufacturing deviation between the individual injectors is compensated for.
[0004]
The object of the present invention is to improve the method of the type described at the outset so that the manufacturing tolerances between the individual injectors can be taken into account even better. Also, the aging characteristics of the injector should be taken into account, all this should be done without deteriorating the exhaust gas characteristics and the fuel consumption of the internal combustion engine.
[0005]
According to the present invention, the object is to at least approximately determine a current valve characteristic curve of a fuel injection device incorporated in an internal combustion engine from torque, and according to the valve characteristic curve, a fuel mass flow to be delivered from the fuel injection device, This is solved by combining the drive control energy supplied to the piezo actuator.
[0006]
Advantages of the Invention The present invention has the advantage that the current valve characteristic curve of each individual fuel injector of an internal combustion engine is known. Such a valve characteristic curve establishes a relationship between each fuel injection quantity to be injected from the fuel injector and the drive control energy to be supplied to the piezo actuator. Since the valve characteristic curve is required at present, the individual parameters of the piezo actuator, such as wear due to aging, and the parameters of the individual injectors, such as changes in the passage characteristics of the exit opening, are taken into account. Is done.
[0007]
Therefore, as in the case of “pilot control”, the individual piezo actuators of the fuel injection device are already sufficiently optimally driven and controlled. In the case of a multi-cylinder internal combustion engine, the subsequent cylinder balance adjustment is intervention controlled only with a very small scale. Optimal operating stability and optimal exhaust gas characteristics are achieved quickly and reliably by the present invention under an internal combustion engine operated using the method according to the present invention.
[0008]
In this case, adaptation is performed not by extending or shortening the injection time of the fuel injection device, but by changing the stroke of the piezo actuator and the flow rate of the fuel during ejection from the fuel injection device. This consideration is based on: That is, in the case of a piezo actuator, the stroke of the piezo actuator depends on the energy supplied to itself. That is, the stroke amount of the piezo actuator is increased or decreased according to the strength of the supplied energy, and the amount of fuel injected is also increased or decreased according to the stroke amount of the piezo actuator.
[0009]
Since the current valve characteristic curve of each piezo actuator is known, the stroke amount of the piezo actuator can be set and adjusted very accurately. Thereby, under the method according to the invention, the start time of injection and the end time of injection can be selected exclusively for optimal combustion with optimal exhaust gas characteristics and optimal fuel consumption characteristics.
[0010]
According to the present invention, there is also an advantage that it is possible to effectively compensate for wear of the piezo actuator caused by aging. This can be achieved by always reflecting the valve characteristic curve sufficiently sufficiently. It should be understood that this “current” concept here does not simply mean that the individual valve characteristic curves must always be determined constantly. The valve characteristic curve should be determined so that the wear due to aging can be grasped as well as possible.
[0011]
Due to the information on the current valve characteristic curve, the manufacturing deviation between the individual injectors can also be taken into account very well. Since the stroke volume and the fuel flow rate of the individual injectors can be set with very high precision by the benefits of the method according to the invention, the exhaust gas characteristics and the fuel consumption are always constant in an internal combustion engine operating under the method according to the invention. It will be optimal.
[0012]
Advantageous embodiments of the invention are described in the dependent claims.
[0013]
According to the first embodiment, the following method steps are included. That is,
Determining from the torque a fuel amount based at least theoretically on the torque;
Obtaining a corresponding fuel mass flow rate from the fuel amount and the corresponding fuel injector opening time;
Forming a value pair from the fuel mass flow rate and drive control energy relating to the injection and torque of the piezo actuator;
A step of selecting a valve characteristic curve following the value pair from a plurality of existing valve characteristic curves for the actuator based on the value pair including the drive control energy and the fuel mass flow rate is included.
[0014]
For example, a plurality of valve characteristic curves or a complete group of valve characteristic curves can be stored in the memory. Since the normal valve characteristic curves that form the relationship between the amount of fuel to be injected and the drive energy required for it do not overlap, the unambiguous mapping of the optimal function is the existence of a unique value pair. Only with this is already possible with high reliability. The valve characteristic curve stored in the memory is obtained by a prior trial. They cover the usual aging and wear effects as well as manufacturing deviations.
[0015]
It should be understood that this method is performed only in the stratified charge mode of the internal combustion engine. This is related to the fact that there is a direct relationship between the torque resulting from the individual injections and the amount of fuel injected only in the stratified charge mode. Of course, it should also be understood that the determined valve characteristic curve can also be used in the “homogeneous combustion mode” of the internal combustion engine and that it leads to the advantages according to the invention. In this mode of operation, the fuel is sufficiently homogeneously present in the combustion chamber and the torque also depends on the mass of air supplied (flow rate). This air mass (flow rate) is normally set by the position of the throttle valve.
[0016]
Advantageously, the drive control voltage of the piezo actuator is reduced from a value above the voltage at which the valve element belonging to the piezo actuator is approximately in a state where the fuel mass flow is determined by the seat throttle, and at the same time the drive control voltage Torque based on the injection performed during the reduction period is monitored and a value pair consisting of fuel mass flow and drive control energy is formed when this torque is reduced by at least one predetermined value.
[0017]
This is based on the following knowledge. That is, according to the characteristic curve of the fuel injection device provided with the piezo actuator, the fuel mass flow rate rises relatively steeply after the valve element moves away from the seat in the first stroke region, and in the subsequent second stroke region. Is already known to fall flat. In this second region, an increase in the stroke of the valve element virtually no longer results in an increase in fuel mass flow. The first region is defined by a so-called “stroke throttle”, and the second region is defined by a so-called “seat throttle”. Here, the characteristic curves of the fuel injectors with different manufacturing tolerances under different aging and wear conditions are distinguished, especially in the stroke throttle region, whereas the seat throttle region They are known to be close to each other.
[0018]
The passage characteristic curve can be associated with the predetermined value pair with higher accuracy in the stroke throttle region. Furthermore, the method can also be carried out in the normal operating mode of the internal combustion engine. With a torque drop of about 5%, which is already invisible to the user of the internal combustion engine, it is possible to determine a value pair that enables selection of an appropriate characteristic curve with high accuracy. In this case, the period during which the drive control voltage is reduced is very short, typically less than 1 second.
[0019]
Alternatively, the change in drive control energy forms a series of value pairs consisting of drive control energy and fuel mass flow, from which the fuel mass to be delivered from the fuel injector. A valve characteristic curve may be formed in which the flow rate and drive control energy to be supplied to the piezo actuator are combined. In this method, instead of searching for a function, the function is formed from a number of value pairs that cover as much as possible the entire region of the characteristic curve. This method enables very accurate mapping of the current characteristic curve of the fuel injector.
[0020]
Furthermore, according to another possibility for carrying out the method of the invention, a value pair consisting of drive control energy and fuel mass flow is determined at various operating points of the internal combustion engine, from a standard function, in particular a fuel injector. An exponential function, which combines the fuel mass flow to be delivered and the drive control energy to be supplied to the piezo actuator, is adapted to the value pairs in question, thereby forming a valve characteristic curve. In the case of this variant embodiment according to the invention, only a small storage capacity is required for the mapping of the characteristic curves.
[0021]
In this case, the adaptation is particularly preferably performed by the method of least squares. This keeps the deviation of the standard function to be adapted as small as possible by the actual value pair.
[0022]
Under the method, value pairs are formed by changing the drive control energy. In this case, it is particularly advantageous that the drive control energy is gradually changed each time. Thereby, after the change of the drive control energy, the characteristics in the internal combustion engine are first stabilized. This increases the accuracy in determining value pairs.
[0023]
Furthermore, this method is carried out within a predetermined time interval. Aging and wear in the fuel injector or the piezo actuator of the fuel injector can be considered reliably over the life of the fuel injector. The corresponding definition of the time interval ensures that the deviation between the current characteristic curve of the fuel injector and the last determined characteristic curve does not exceed a predetermined range. The concept of “time interval” here is to be understood as the true operating time or number of fuel injector operations.
[0024]
Particularly advantageously, an entry into the error memory and / or a notification is sent out when the drive control energy of the piezo actuator required for delivery of a predetermined fuel mass flow rate has reached at least one threshold value. . This identifies extreme characteristic curves that can lead to particularly high wear and severe aging of the fuel injectors and piezo actuators and provides relevant information to users or technicians who maintain the internal combustion engine.
[0025]
The invention further relates to a computer program suitable for carrying out the above-described method when implemented on a computer. In this case, the computer program is particularly preferably stored in a memory, in particular a flash memory or a ferrite memory.
[0026]
The invention further relates to an open loop and / or closed loop control device for the operation of an internal combustion engine. Particularly advantageously in this case it comprises a memory in which a computer program of the form described above is stored.
[0027]
The present invention also provides at least one fuel injection device that includes a piezo actuator and directly injects fuel into the combustion chamber, and determines the torque formed under the combustion of the amount of fuel injected into the combustion chamber during injection. It also relates to an internal combustion engine having a device capable of performing the above.
[0028]
In order to maintain the fuel economy and exhaust gas characteristics of the internal combustion engine and the operational stability over the life of the internal combustion engine, the internal combustion engine includes an open loop and / or closed loop control device of the type described above.
[0029]
In the following description, particularly advantageous embodiments of the invention are described in detail with reference to the associated drawings. In this case, FIG. 1 is a basic principle diagram of a region of an internal combustion engine having a fuel injection device.
FIG. 2 is a diagram in which the fuel mass flow is plotted over the stroke amount of the valve element of the fuel injection device according to FIG.
FIG. 3 is a characteristic curve showing the fuel mass flow and torque over the drive control voltage of the piezo actuator of the fuel injection device according to FIG.
4 is a flow chart representing a first embodiment of a method for operating the internal combustion engine of FIG.
FIG. 5 is a diagram similar to FIG. 3 for illustrating the method according to FIG.
FIG. 6 is a flow chart representing a second embodiment of the method for operating the internal combustion engine according to FIG.
FIG. 7 is a diagram similar to FIG. 3 for illustrating the method according to FIG.
FIG. 8 is a flow chart representing a third embodiment of the method for operating the internal combustion engine according to FIG.
FIG. 9 is a diagram similar to FIG. 3 for illustrating the method according to FIG.
【Example】
[0030]
The internal combustion engine of FIG. This internal combustion engine has a plurality of combustion chambers, only one of which is represented by reference numeral 12 in FIG. Combustion air is supplied to the combustion chamber from the intake pipe 14 via the intake valve 16. The combustion exhaust gas is exhausted to the exhaust pipe 20 through the exhaust valve 18.
[0031]
The fuel is directly injected into the combustion chamber 12 via the fuel injection device 22. This injection device is an injector, and its valve element (not shown) is movable by a piezo actuator (not shown). This injector 22 is connected to a fuel system 24. This fuel system supplies fuel to the injector 22 under very high pressure. The fuel / air mixture in the combustion chamber 12 is ignited by the spark plug 26. This spark plug 26 is connected to an ignition system 28.
[0032]
The rotation number of the crankshaft 30 and its angular position and angular acceleration are detected by a sensor 32. Corresponding signals are supplied to the open loop / closed loop controller 34. The open loop / closed loop control device 34 drives and controls the injector 22, for example.
[0033]
The stroke throttle characteristic curve of the injector 22 is shown in FIG. 2, and from this characteristic curve, the fuel mass flow rate Qstat rises sharply in the first region (stroke throttle region 36) of the stroke h. In the further course of the stroke h of the valve element of the injector 22, the fuel mass flow is virtually no longer rising (seat throttle zone 38). The stroke throttle area 36 is important. This is because many small injections result in a large amount of fuel. In this case, the injector 22 is only slightly opened. The injector remains substantially in the stroke throttle area 36.
[0034]
Based on the aging, wear, manufacturing tolerance, etc. of the piezo actuator of the fuel injection device 22, the predetermined drive control voltage U (see FIG. 3) of the piezo actuator is not for each injector 22 but for the same injector 22. , Which leads to the same fuel mass flow rate Qstat, regardless of its total lifetime. As can be seen from FIG. 3, the same injector 22 has different characteristic curves a, b, c (Qstat = f (U)) over its lifetime. Other different injectors 22 represent correspondingly different characteristic curves based on the aforementioned manufacturing tolerances.
[0035]
In the stratified fuel mode, the torque M of the internal combustion engine 10 is determined almost exclusively by the amount of fuel injected, and similarly from FIG. 3, the drive of the piezoelectric actuator of the injector 22 by these characteristic curves. Not only is the relationship between the control voltage U and the fuel mass flow rate Qstat established, but the relationship between the drive control voltage U and the torque M can also be established.
[0036]
In order to avoid different fuel mass flow rates Qstat being supplied to the individual combustion chambers 12 due to manufacturing tolerances of the injectors 22 under the same drive control voltage U under the multi-cylinder internal combustion engine 10, and In order to compensate for the appearance of the aging of the injector 22 over the operating period, the internal combustion engine 10 according to FIG. 1 is operated according to the method shown in FIG. 4 (this method is an open loop / closed loop as a computer program). Stored in the controller 34).
[0037]
After the start block 40, an inquiry is made at block 42 as to whether the internal combustion engine 10 is currently operating in a stratified intake mode. This query is important because there is a direct relationship between torque M and fuel mass flow rate Qstat only in stratified intake mode. This direct relationship makes it possible to determine the characteristic amount necessary for compensating for the deviation as described above, as will be described in detail below.
[0038]
In block 44, an inquiry is made as to whether the characteristic curve of the injector 22 should be examined. Such an inspection is not always necessary and is done at predetermined periodic intervals. If the result of this block 44 is “yes”, a query is made in block 46 as to whether the drive control voltage U is greater than the limit value G1. This ensures that the internal combustion engine 10 is at an operating point where the valve element of the injector 22 belonging to the piezo actuator is at a position where the fuel mass flow rate Qstat is determined approximately by the seat throttle. The limit value G1 is also shown in FIG. 5, where the seat throttle area is to the right of the corresponding wavy line. In block 48, the drive control voltage U is gradually reduced.
[0039]
As soon as the fuel mass flow Qstat is determined approximately by the stroke throttle, the corresponding torque M also decreases under the reduction of the drive control voltage U. In block 50, it is detected whether this torque drop dM exceeds a limit value G2. This torque is represented by symbol MG2 in FIG. Only the small fuel mass flow rate QstatG2 is determined from the torque MG2. One value pair is formed from the drive control voltage UG2 contributing to the injection that provides the torque MG2 and the fuel mass flow rate QstatG2.
[0040]
In block 52, a value following the value pair UG2 and QstatG2 is selected from a plurality of characteristic curves fa, fb, fc, fd, and fe stored in the memory. As is clear from FIG. 5, this is a full tooth and a characteristic curve fc. This is now stored in the memory 54. The method then ends at the last block 56. Possible stroke throttle characteristic curves fa, fb, fc, fd, and fe are obtained in advance by trial and stored in the open loop / closed loop control device 34.
[0041]
However, if the value pair UG2, QstatG2 exists, for example, so that the valve characteristic curve fe comes next, an additional entry to the error memory is made and a message is sent to the user. This may be due to, for example, a blinking warning lamp provided on the dashboard of the automobile in which the internal combustion engine 10 is incorporated.
[0042]
In detail, the valve characteristic curve fe means that the fuel injection device 22 is deteriorated as follows. That is, in order to deliver a predetermined fuel mass flow rate, it is aged deterioration that requires drive control energy above the threshold (this threshold is not shown in FIG. 5). The user and the mechanic performing maintenance of the internal combustion engine are suggested to the corresponding state of the fuel injector. At the same time, however, it is also ensured that the fuel mass flow can be controlled open-loop or closed-loop as desired.
[0043]
FIG. 6 shows a second embodiment of the method, in which the operation of the internal combustion engine according to FIG. 1 is possible. In this flowchart and the following flowchart, the same reference numerals are given to the same functions as the blocks in FIG. 4, and the detailed description thereof will not be repeated.
[0044]
In the method shown in FIG. 6, the corresponding characteristic curve in the current state of the fuel injector 22 is not selected from a plurality of characteristic curves prepared in advance, but dedicated to the fuel injector 22 concerned. Created. This is done as follows. In other words, the driving control voltage U of the fuel injection device 22 is gradually increased under the operating internal combustion engine 10. The corresponding fuel mass flow rate Qstati is determined via the corresponding torque M.
[0045]
In this way, the value pair Ui, Qstati is created. From this series of value pairs, a function f (U, Qstat) is finally formed (block 60), which is the fuel mass flow rate Qstat to be delivered by the fuel injector 22 and the piezo actuator. The drive control energy U to be supplied is combined. This combination can be performed by linear interpolation. However, it should be understood that the method illustrated in FIGS. 6 and 7 may not be performed during the normal operating mode of the internal combustion engine 10 but should be performed, for example, during a maintenance period.
[0046]
In the case of the method for operation of the internal combustion engine 10 shown in FIG. 8, during block 62 during the normal operation mode of the internal combustion engine 10 (stratified intake mode), data vs. Ui (drive control voltage) and Qstati (fuel mass flow rate) is stored. If a sufficient number of data pairs Ui, Qstati are available, exponential characteristic curve adaptation using error least squares is performed in block 64 (U = a · e ^b−Qstat ). In this characteristic curve adaptation, the coefficients a and b are determined such that the accepted value pair Ui, Qstati is as far as possible from the corresponding characteristic curve (U = a · e ^b−Qstat ) (FIG. 9).
[0047]
It should be particularly emphasized here that each of the above-described methods is carried out for each individual cylinder or each individual fuel injector 22 under a multi-cylinder internal combustion engine. The correspondence between the torque formed by the injection into the combustion chamber 22 and the corresponding combustion chamber 12 is performed via the angular position of the crankshaft 30. This angular position is detected by the sensor 32. The torque formed by the combustion of the fuel injected into the combustion chamber 12 is detected by measuring the acceleration of the crankshaft 30 caused by the combustion. The acceleration of the crankshaft 30 is also obtained from the signal of the sensor 32.
[Brief description of the drawings]
[0048]
FIG. 1 is a basic principle diagram of a region of an internal combustion engine having a fuel injection device. FIG. 2 is a diagram in which a fuel mass flow rate is plotted over a stroke amount of a valve element of the fuel injection device according to FIG. FIG. 4 is a characteristic curve showing the fuel mass flow rate and torque over the drive control voltage of the piezo actuator of the fuel injection device according to FIG. 4; FIG. 4 is a flowchart representing a first embodiment of the method for operating the internal combustion engine of FIG. FIG. 5 is a diagram similar to FIG. 3 for explaining the method according to FIG. 4; FIG. 6 is a flow chart representing a second embodiment of the method for the operation of the internal combustion engine according to FIG. FIG. 8 is a diagram similar to FIG. 3 for illustration. FIG. 8 is a flowchart representing a third embodiment of the method for the operation of the internal combustion engine according to FIG. 1. FIG. Diagram similar to FIG. 3 of the order

Claims (13)

A method for the operation of an internal combustion engine (10), wherein fuel is injected directly into at least one combustion chamber (12) via at least one fuel injection device (22), said fuel injection device (22) In the operating method of the internal combustion engine of the type in which the torque (M) generated under the combustion of the amount of fuel injected into the combustion chamber (12) during injection is determined by a piezo actuator.
From the torque (M), the current valve characteristic curve (f) of the fuel injector (22) incorporated in the internal combustion engine (10) is at least approximately determined (52; 60; 64),
The valve characteristic curve (f) combines the fuel mass flow rate (Qstat) to be delivered from the fuel injection device (22) and the drive control energy (U) to be supplied to the piezo actuator. Feature method. Determining from the torque (MG2) a fuel amount based at least theoretically on the torque (MG2);
Obtaining a corresponding fuel mass flow rate (QstatG2) from the fuel amount and the corresponding open time of the fuel injector (22);
Forming a value pair (UG2, QstatG2) from the fuel mass flow rate (QstatG2) and drive control energy (UG2) related to the piezoelectric actuator injection and torque (MG2);
Based on the value pair (UG2, QstatG2) consisting of the drive control energy (UG2) and the fuel mass flow rate (QstatG2), the existing valve characteristic curves (fa, fb, fc, fd, fe) for the actuator 2. The method of claim 1, further comprising the step of selecting (52) a valve characteristic curve (fc) following the value pair (UG2, QstatG2). The drive control voltage (U) of the piezo actuator is reduced from a value above the voltage (G1) at which the valve element belonging to the piezo actuator becomes approximately in a state where the fuel mass flow rate (Qstat) is determined by the seat throttle (48 ),
At the same time, the torque (M) based on the injection performed during the reduction period of the drive control voltage (U) is monitored (50),
When this torque (M) decreases by at least one predetermined value (G2), a value pair (QstatG2, UG2) consisting of fuel mass flow rate (QstatG2) and drive control energy (UG2) is formed (52) The method of claim 2. A change (58) in the drive control energy (U) forms a series of value pairs (Ui, Qstati) consisting of the drive control energy (Ui) and the fuel mass flow rate (Qstati), and these series of value pairs (Ui, Qstati) forms a valve characteristic curve (f) that combines the fuel mass flow (Qstat) to be delivered from the fuel injector (22) with the drive control energy (U) to be supplied to the piezo actuator. (60) The method according to claim 1. At various operating points of the internal combustion engine (10), a value pair (Ui, Qstati) consisting of drive control energy (Ui) and fuel mass flow rate (Qstati) is determined (62), standard function (f), in particular fuel injection. Exponential function adapts to multiple pairs of values (Ui, Qstati), combining the fuel mass flow (Qstat) to be delivered from the device (22) and the drive control energy (U) to be supplied to the piezo actuator The method of claim 1 wherein the valve characteristic curve (f) is formed. The method of claim 5, wherein the adaptation (64) is performed by least squares. The method according to any one of claims 3 to 6, wherein the drive control energy (U) is each gradually changed (48, 58). The method according to claim 1, wherein the method is periodically performed within a predetermined time interval. An error memory entry is performed and / or a notification is sent out when the drive control energy of a piezo actuator required for delivery of a predetermined fuel mass flow reaches at least one threshold value. 8. The method according to any one of claims 8. Computer program suitable for carrying out the method according to any one of claims 1 to 9 when implemented on a computer. Computer program according to claim 10, stored on a memory, in particular a flash memory or a ferrite memory. 12. An open loop and / or closed loop control device (34) for the operation of an internal combustion engine, comprising a memory in which a computer program according to claim 10 or 11 is stored. At least one fuel injector (22) including a piezo actuator and directing fuel directly into the combustion chamber (12);
In an internal combustion engine (10) having a device (32) capable of determining a torque (M) formed under combustion of an amount of fuel injected into a combustion chamber (12) due to a difference in injection ,
Internal combustion engine comprising an open loop and / or closed loop control device (34) according to claim 12.

Images