JP2004076732A - Method for individualizing injector for internal combustion engine with piezoelectric element, control method for piezoelectric element, injector and internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To facilitate the use of knowledge obtained by describing the actual characteristics of an injector with a piezoelectric element in a more detailed manner. <P>SOLUTION: The stroke of the piezoelectric element 22 is detected 28 depending on applied voltage, and a code 24 is formed in accordance with a detected voltage/stroke ratio to characterize 40 the injector 14. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The invention relates to a method for individualizing an injector of an internal combustion engine provided with a piezoelectric element, wherein at least one electromechanical characteristic of the individual injector is detected.
[0002]
[Prior art]
Methods of the type mentioned at the outset are known. Here, the amount of liquid injected from the injector is detected depending on the control duration. The amount of liquid that depends on the control duration is an electromechanical property. For this purpose, for example, a value pair for the control duration and the quantity of liquid to be injected is determined in four different operating states. The corresponding adjustment value is recorded in the injector in the form of a six-digit code. When the corresponding injector is installed, this code is input to the control of the internal combustion engine, from which an adaptive and multiplicative correction value for the control duration is determined.
[0003]
The purpose of this measure, also referred to as "quantity control", is to bring the fuel to the combustion chamber of the internal combustion engine with the highest possible accuracy. Injectors with piezoelectric adjustment elements are preferably used in internal combustion engines with direct fuel injection. In such an internal combustion engine, it is very important to meter the fuel into the combustion chamber with high accuracy. The piezoelectric elements used in the known injectors operate very fast, but have the disadvantage that their operating characteristics, or at least one electromechanical characteristic, can differ from piezoelectric actuator to piezoelectric actuator. This difference is detected to some extent by the above amount adjustment, and this difference is taken into account by correction in the control device.
[0004]
[Problems to be solved by the invention]
It is an object of the present invention to better describe the actual characteristics of an injector provided with a piezoelectric element and to facilitate the use of the obtained knowledge.
[0005]
[Means for Solving the Problems]
This object is achieved in a method of the type mentioned at the outset by detecting the stroke of the piezoelectric element as a function of the applied voltage, forming a code from this detected voltage / stroke characteristic and representing the injector by this code. Will be resolved.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
The function of the injector can be particularly well described by the method according to the invention. Variations in the stroke of the piezoelectric element at a given control voltage affect the amount of fuel injected from the injector during injection. If the voltage / stroke characteristics of the individual injectors are known and the injectors are appropriately characterized, it is possible to respond accordingly when using the injectors. Finally, the method according to the invention achieves high accuracy in metering the amount of fuel injected into the combustion chamber.
[0007]
By encoding the detected characteristics, the injector can be filed despite the generally small dimensions of the injector having characteristics that characterize the piezoelectric actuator of the injector. This can be done, for example, in the form of a barcode or in the form of a transponder chip located on the injector. Generally, the code digit is 5 bits. The display can be made with letters and numbers. Therefore, this code digit is usually sufficient to characterize the injector by voltage / stroke characteristics.
[0008]
Advantageous refinements of the invention are set out in the dependent claims.
[0009]
For example, it is proposed to assign an individual injector to one of a plurality of voltage / stroke classes depending on the detected voltage / stroke ratio, and to characterize the injector with a code corresponding to one of the individual voltage / stroke characteristics. . In this refinement, it is sufficient for the injector to store only the region of the voltage / stroke class to which the actually detected voltage / stroke ratio belongs, rather than the actually detected voltage / stroke ratio, in the injector. It is based on the idea. This saves memory space and simplifies the processing of such code.
[0010]
The amount of liquid delivered from the injector is detected as a function of the control duration, and the individual injectors are assigned to one or more control duration / liquid quantity classes depending on the detected liquid quantity, and the injector is assigned to the injector. Advantageously, it is characterized by a code corresponding to the individual control duration / liquid quantity class. In this case, the characterization of the injector takes place not only by the stroke adjustment described at the outset, but also additionally by a volume adjustment. The characterization of such injectors is therefore particularly accurate. Classifying the actually detected liquid volume into a control duration / liquid volume class reduces the required memory space in the same way as the voltage / stroke ratio. A six-digit code is preferably provided for the quantity adjustment.
[0011]
The subject of the invention is also a method for controlling a piezoelectric element, in which a control target value is corrected depending on the individual electromechanical properties of the injector, which characterizes the injector.
[0012]
In such a method, control is performed so that fuel is delivered from the injector to the combustion chamber of the internal combustion engine with high accuracy.
[0013]
For this purpose, a code characterizing the injector is detected, which code is based on the individual relationship between the applied voltage and the travel of the piezoelectric element, and corrects the control target value depending on the detected code. It is.
[0014]
The advantage of this method is that the voltage / stroke ratio of the individual injector is detected and processed simply and quickly based on the coding. Correction of the control setpoint based on the individual voltage / stroke ratios furthermore enables particularly precise operation of such injectors. The difference in the amount of fuel actually injected by the individual injectors into the combustion chamber of the internal combustion engine is very small using the method according to the invention.
[0015]
It is advantageous here to determine the characteristic class of the voltage / stroke ratio from the code characterizing the injector. Such a classification into characteristic classes can reduce the required memory space in the injector. Furthermore, properties classified in this way can be processed very quickly and easily.
[0016]
In a further refinement of the method according to the invention, a characteristic class of the control duration / liquid quantity ratio is determined from a code characterizing the injector. The additional consideration of the control duration / liquid quantity ratio, which results from the quantity adjustment, further improves the accuracy when metering the fuel quantity injected from the injector.
[0017]
Particularly advantageously, in a refinement of the method according to the invention, the code is detected automatically upon installation of the injector. As a result, the control device of the internal combustion engine can automatically identify the characteristics of the injector used, for example, without the need for programming on the part of the user, and the parameters (additive) required for optimal operation of the injector. And / or a multiplicative correction value). Even if the injector is replaced, for example, for maintenance work, the code of the newly used injector is automatically detected and the control device automatically detects the corresponding correction value.
[0018]
Furthermore, the subject of the present invention is an injector for injecting fuel into a combustion chamber of an internal combustion engine and having a piezoelectric element.
[0019]
In order to drive such an injector as accurately as possible, it is proposed that this injector have a code based on a discrete ratio between the applied voltage and the travel of the piezoelectric element.
[0020]
The invention further relates to an internal combustion engine having at least one injector and at least one combustion chamber through which fuel is supplied. Here, the injector has a piezoelectric element.
[0021]
In order to optimize the exhaust gas characteristics of such an internal combustion engine, minimize fuel consumption and achieve quiet operation of such an internal combustion engine, the internal combustion engine has a reading device, and the reading device controls the injector. It is proposed to characterize and detect a code based on the individual ratio between the applied voltage and the travel of the piezoelectric element.
[0022]
The individual identifier, ie the electromechanical properties of the injector, can be easily detected by the readout device. If the individual electromechanical properties of the injectors are known, the correction of the control signal can respond to differences existing between the individual injectors of the internal combustion engine. As a result, it is possible to inject a desired amount of fuel from each injector into the combustion chamber of the internal combustion engine with high accuracy. This improves the quietness of operation of the internal combustion engine, reduces fuel consumption, and improves the exhaust gas characteristics of the internal combustion engine.
[0023]
【Example】
In FIG. 1, an internal combustion engine is indicated generally by the reference numeral 10. The internal combustion engine has a plurality of combustion chambers, of which only one is designated by reference numeral 12 in FIG. Fuel is supplied to the combustion chamber 12 directly from the injector 14. The fuel supplied can be gasoline, in which case an ignition device is additionally provided in the combustion chamber 12. However, the fuel used may be diesel fuel.
[0024]
The injector 14 is connected to a fuel collection line 16 (rail), in which fuel is stored under very high pressure. Additional injectors are also connected to the fuel collection line 16, but these are not shown. The separate injectors also inject fuel directly into the combustion chambers assigned to them. The pressure in the fuel collecting line 16 is detected by a pressure sensor 18, which sends a corresponding signal to the control device 20.
[0025]
The injector 14 has a movable valve element (not shown), which is connected to a piezoelectric actuator 22. The drive of the piezoelectric actuator 22 is also controlled by the control device 20. Here, the piezoelectric actuator changes its length by applying a voltage to the piezoelectric actuator 22, which is transmitted to the position of the valve element of the injector 14. However, the speed at which the change in the length of the piezoelectric actuator responds to the voltage change differs from one piezoelectric actuator to another. Further, the stroke of the piezoelectric actuator at a predetermined control voltage is different from the strokes of other piezoelectric actuators even when the control voltage is the same.
[0026]
Characteristics that differ from piezoelectric actuator to actuator are due to the system and cannot be prevented at present. However, this difference results in the fact that, if no countermeasures are taken, more fuel is injected into the combustion chamber than with the other combustion chambers of the same internal combustion engine, even with the same control voltage.
[0027]
In order to adjust the amount of fuel injected from the injector 14 into the combustion chamber 12 as accurately as possible, the injector 14 is measured before it is used in the internal combustion engine 10. In particular, the stroke characteristic is determined as a function of the voltage, as well as the quantity of liquid injected from the injector as a function of the control duration, and this detected “electromechanical” characteristic is converted into a code 24. This cord is attached to the casing of the injector 14 in the embodiment shown in FIG. The code 24 is read by a reading device 26 fixedly arranged on the internal combustion engine 10, which supplies a corresponding signal to the control device 20.
[0028]
To detect the individual electromechanical properties of the injector and to characterize the injector 14 with the corresponding code 24, the following takes place (see FIG. 12):
In block 28, the stroke capability of the piezoelectric actuator 22 is measured. For this purpose, the drive of the piezoelectric actuator 22 is controlled by a predetermined voltage, and a corresponding change in the length of the piezoelectric actuator 22 is detected. Depending on the detected voltage / stroke characteristics of the piezo actuator 22, one of a plurality of voltage / stroke classes corresponding to the actual characteristics of the injector 14 is selected in block 30. In a block 32, a grade corresponding to the travel capability of the piezoelectric actuator 22 is converted into a code. For this reason, in this embodiment, the code digit is one digit, that is, 5 bits.
[0029]
In parallel with the measurement of the stroke capacity, the injector 14 also performs a so-called volume adjustment. In this quantity adjustment, the quantity of liquid delivered from the injector 14 is detected with different control durations. Here, it is sufficient to detect four different inspection points as a whole. This is done in block 34 of FIG. As in block 30, in block 36 the characteristics of the injector 14 detected in block 34 are classified. As with block 32, at block 38 the grades detected at block 36 are converted to codes. This code is 6 digits with 5 bits each in this embodiment. That is, it is 30 bits in total.
[0030]
In block 40, the entire encoding shown in FIG. 1 is performed from the two encodings obtained in blocks 32 and 38, and the resultant is attached to the injector 14.
[0031]
The process executed when the information stored in the code 24 is read will be described with reference to FIG.
[0032]
In block 42, the code 24 is read by the reading device 24 and a corresponding signal is passed to the control device 20. In a subsequent block 44, the signal notified is decoded, and in a block 46, an additive and multiplicative correction value is detected for the control voltage of the piezoelectric actuator 22 of the injector 14 from the class obtained from the code 24. In block 48, an individual control voltage for the injector 14 is determined based on the correction parameter detected in block 46 and the control voltage set in block 50 in order to accurately inject fuel into the combustion chamber 12.
[0033]
The control voltage provided in block 50 depends inter alia on the pressure in fuel collection line 16. This pressure is detected by the pressure sensor 18 and notified to the control device 20. In block 52, the corresponding output stage is then controlled. The same method as the method shown in FIG. 3 is performed for the encoding of the amount adjustment set in the block 38.
[0034]
The method steps set in blocks 42 to 46 need not be performed for each injection of the injector 14. These method steps are performed once after the injector 14 is mounted on the internal combustion engine 10. The correction values detected in block 46 are stored and used during each injection of the injector 14.
[Brief description of the drawings]
FIG. 1 is a schematic view of an injector having a plurality of components of an internal combustion engine, in particular a piezoelectric element.
2 is a flowchart of a method for characterizing individual characteristics of the injector of FIG.
FIG. 3 is a flowchart of a method for using the injector of FIG. 1;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Combustion chamber 14 Injector 16 Fuel collection line 18 Pressure sensor 20 Control device 22 Piezoelectric actuator 24 Code 26 Reading device

Claims (9)

A method for individualizing an injector (14) of an internal combustion engine (10) provided with a piezoelectric element (22), wherein the method detects at least one electromechanical characteristic of the individual injector (14).
Detecting the stroke of the piezoelectric element (22) depending on the applied voltage (28);
Forming a code (24) from the detected voltage / stroke ratio;
Characterizing the injector (14) with the code (40);
A method comprising: Assigning individual injectors (14) to one of a plurality of voltage / stroke classes depending on the detected voltage / stroke ratio (30);
2. The method according to claim 1, wherein the injector is characterized by a code corresponding to one of the individual voltage / stroke ratings. Detecting the amount of liquid injected from the injector (14) depending on the control duration (34);
Assigning the individual injectors (14) to one of a plurality of control duration / liquid quantity classes depending on the detected liquid quantity (36);
3. The method according to claim 2, wherein the injector is characterized by a code corresponding to a respective control duration / liquid quantity class. A method of controlling an injector (14) provided with a piezoelectric element (22), wherein the control target value is corrected depending on individual electromechanical characteristics characterizing the injector (14),
Detecting a code (24) characterizing the injector (14),
The code (24) is based on an individual ratio between the applied voltage and the travel of the piezoelectric element (22),
Correcting the control target value depending on the detected code (24) (48);
A method comprising: 5. The method according to claim 4, wherein the characteristic class of the "voltage / stroke ratio" characteristic is detected from the code characterizing the injector. 6. The method according to claim 4, wherein the characteristic class of the "control duration / liquid amount ratio" characteristic is determined from a code characterizing the injector. 7. The method according to claim 5, wherein the code is detected automatically or at the time of installation of the injector. An injector (14) for injecting fuel into a combustion chamber of an internal combustion engine (10), the injector having a piezoelectric element (22),
The injector has a code (24);
The code is based on a discrete ratio between the applied voltage and the travel of the piezoelectric element (22),
An injector characterized in that: An internal combustion engine (10) having at least one injector and at least one combustion chamber (12), wherein fuel is injected into said combustion chamber via an injector (14),
The injector (14) is an internal combustion engine having a piezoelectric element (22),
The internal combustion engine (10) has a reading device (26),
The code (24) is detected by the reader,
The code characterizes the injector (14),
The code is based on a discrete ratio between the applied voltage and the travel of the piezoelectric element (22),
An internal combustion engine characterized in that:

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