DE102004028612B4 - Method for operating an internal combustion engine, and computer program, control and / or regulating device, and internal combustion engine - Google Patents

Abstract

Method for operating an internal combustion engine (10), in which fuel via a fuel injection device (26), which comprises a capacitive adjusting element (50), in a combustion chamber (20) of the internal combustion engine (10), in which a production-specific property of the fuel Injection device (26) is identified in which at least one for a desired first stroke (h1) of the capacitive actuator (50) required first standard charge (Q1 ') is determined, and in which the standard charge (Q1') with a correction value (K1 ), which is obtained taking into account a property-specific correction function (F, OF) and the first desired stroke (h1), characterized in that a for a desired second stroke (h2) of the capacitive control element (50) required second standard charge (Q2 ') and this second standard charge (Q2') with a correction value (K2) is applied, which, taking into account the characteristics spezi correction function (F, OF) and the second stroke (h2) is obtained.

Description

State of the art

The invention relates to a method for operating an internal combustion engine, in which fuel via a fuel injection device, which comprises a capacitive adjusting element, passes into a combustion chamber of the internal combustion engine, in which a production-specific property of the fuel injection device is identified, wherein at least one for a the first desired stroke of the capacitive actuating element required first standard charge is determined, and in which the standard charge is applied to a correction value, which is obtained taking into account a property-specific correction function and the first desired stroke. The invention also relates to a computer program, a control and / or regulating device, and an internal combustion engine, in particular for a motor vehicle.

From the DE 199 58 406 A1 is a capacitive element in the form of a piezoelectric actuator known, which can be used for example for actuating fuel injectors in internal combustion engines.

From the DE 199 58 406 A1 It is also known that with the same design production-related deviations of the properties of a piezoelectric actuator (and / or the associated fuel injection device) may occur from one copy to another. For this reason, the piezoelectric actuators are measured after production and assigned according to their properties to certain property classes.

Furthermore, from the EP 1 311 004 B1 a method for Spannungssollwertberechnung a piezoelectric element as a function of a rail pressure known. The voltage setpoint is corrected by means of a multiplier as a function of a temperature of the piezoelectric element.

After installation of the injector in an internal combustion engine and its connection to a control unit of the controller, the corresponding property class of the actuator is determined. In practice, a standard charge is then first determined based on a standard curve stored in the control unit, which must be applied to the capacitive control element in order to achieve a desired stroke can. This standard charge is then subjected to a correction value according to the identified property class. This is intended to ensure that the amount of fuel actually injected into the combustion chamber of the internal combustion engine from the fuel injection device corresponds as exactly as possible to the desired fuel quantity.

Object of the present invention is to develop a method of the type mentioned so that the fuel can be injected even more precise.

This object is achieved in the aforementioned method in that a second standard load required for a second desired stroke of the capacitive actuating element is determined and this second standard charge is subjected to a correction value obtained taking into account the property-specific correction function and the second desired stroke.

Advantages of the invention

In the method according to the invention, the correction function specific to the respective fuel injection device or the respective capacitive actuating element is applied in such a way that even completely different strokes of the capacitive actuating element can be adjusted with high precision. However, the precise adjustment of even a small stroke of the capacitive actuator is an important prerequisite, especially for the precise injection of very small amounts of fuel. Therefore, the process of the invention as a whole allows the precision in the metering of a certain amount of fuel into a combustion chamber. The improved metering accuracy of the fuel improves the ride comfort, the emission behavior and the consumption behavior of the internal combustion engine.

The basis for this is that different desired or desired strokes and the corresponding standard charges are not linked with the same correction value, but with an individual and optimal correction value for the respective setpoint stroke. It goes without saying that the method according to the invention can be used not only for two different stroke values but for any desired number of different stroke values. The inventive method is particularly advantageous when the corrected standard charge is used for a precontrol of the capacitive steep element. The optionally still necessary control interventions to achieve a certain desired stroke are reduced and thereby improves the dynamics and the stability of the scheme.

Advantageous developments of the invention are specified in subclaims.

A particularly advantageous embodiment of the method according to the invention provides that different within a work cycle Strokes are desired, and that for each desired stroke determines the respectively required standard charge and the standard charge is applied to a correction value, which is obtained taking into account the property-specific correction function and the respective desired stroke. Such different strokes occur, for example, in multiple injections, since in the individual injections very different amounts of fuel are often injected into the combustion chamber of the internal combustion engine (a working cycle is understood, for example, in a four-stroke internal combustion engine, all four strokes of a cylinder). Thus, for example, pre- and post-injections are conceivable in which only extremely small amounts of fuel are to reach the combustion chamber, whereas a comparatively large amount of fuel is to be injected in the case of a main injection lying between pre- and post-injection.

Thanks to the method according to the invention, the property-specific correction to each applied charge, or the corresponding stroke is tuned for each individual injection, which is a very precise determination of the charge required for the desired stroke, and thus in the comparatively small strokes of pre- and post-injection ultimately allows the precise introduction of a desired amount of fuel into the combustion chamber. Ultimately, this in turn improves the emission and consumption behavior of the internal combustion engine.

Furthermore, it is proposed that the desired stroke of an injection is obtained taking into account a desired injection time and an amount of fuel to be injected during injection and / or a fuel pressure present during injection and / or a temperature of the fuel injection device present during the injection. In this way, the amount of fuel injected corresponds particularly well to the desired amount of fuel to be injected.

The application of the correction value can be effected by multiplying the standard charge by a factor and adding an offset to the product. This is programmatically easy to implement.

A current with which the capacitive element is to be fed can be determined very easily from the quotient of the corrected standard charge and a charging time. Such a current is the actual manipulated variable with which the fuel injection is regulated or controlled.

In a computer program, an electrical storage medium for a control and / or regulating device of an internal combustion engine, a control and / or regulating device and an internal combustion engine, the object stated in the introduction is correspondingly achieved.

drawings

Hereinafter, particularly preferred embodiments of the present invention will be explained in more detail with reference to the accompanying drawings. In the drawing show:

1 a schematic representation of an internal combustion engine with a fuel injection device;

2 a schematic section through a portion of the fuel injection device of 1 ;

3 a diagram in which various relationships between a stroke of a capacitive actuator of the fuel injection device of 1 and an applied charge are applied;

4 a diagram in which the stroke of the capacitive actuator of the fuel injection device of 1 at a main injection and at a post-injection over time is plotted;

5 a diagram in which the state of charge of the capacitive adjusting element of the fuel injection device of 1 at the main injection and the post-injection of 4 is plotted over time; and

6 a flowchart showing a method for determining a setpoint for a charge current for the injections of 4 and 5 shows.

Description of the embodiments

In 1 an internal combustion engine carries the reference numeral 10 , It is installed in a motor vehicle and includes several cylinders, one of which is in 1 only one is shown, which is the reference numeral 12 wearing. There is a piston in it 14 taken, which is a crankshaft 16 drives. The speed of the crankshaft 16 is from a speed sensor 18 tapped.

A combustion chamber 20 of the cylinder 12 is combustion air through an inlet pipe 22 and one in 1 not shown inlet valve supplied. The combustion gases are discharged from the combustion chamber 20 over an exhaust pipe 24 dissipated, which has a in 1 also not shown exhaust valve with the combustion chamber 20 connected is. fuel gets to the combustion chamber 20 about as an injector 26 trained fuel injector directly injected. The injector 26 is with a fuel system 28 connected, which in 1 is shown only symbolically. It comprises a fuel tank, a prefeed pump, a main feed pump and a fuel rail in which the fuel is stored under high pressure. The injector 26 is connected to the fuel rail and into a head of the cylinder 12 the internal combustion engine 10 built-in.

He is in the combustion chamber 20 Fuel is from a spark plug 30 inflamed. This receives the energy required for an ignition from an ignition system 32 , The ignition system 32 is in turn by a control and / or regulating device 34 driven. This is the output side via a power amplifier 35 also with the injector 26 connected and controls this. The final stage 35 can in the control and / or regulating device 34 be integrated. On the input side receives the control and / or regulating device 34 Signals from a temperature sensor 36 which determines the temperature of the injector 26 detected. Alternatively it is possible that the temperature of the injector 26 , Especially with the help of modeling from other operating variables of the internal combustion engine 10 , for example, from the engine temperature, is determined so that the temperature sensor 36 in this respect can be omitted. Furthermore, the speed sensor is also 18 with the control and / or regulating device 34 connected. A positioner 38 , which indicates the position of an accelerator pedal 40 picks up, also supplies signals to the control and / or regulating device 34 ,

The control and / or regulating device 34 can be constructed as an analog electronic circuit. Preferably, it has a computer, for example a microprocessor with a flash memory. Furthermore, the control and / or regulating device 34 connected to the described sensors and actuators, so that they process their signals, or generate signals to their control can. A computer program with a plurality of program instructions is stored on the flash memory. The computer program is thereby able to carry out the methods described below, when it runs on the microprocessor.

In 2 is the injector 26 shown in more detail. It comprises a valve body 42 , at the brennraumseitigem end in the in 2 open state shown an outlet 44 for the fuel is present. This can be done by means of a valve needle 46 with an annulus 48 connected, in turn, with the fuel system 28 connected is. That from the outlet 44 opposite end of the valve needle 46 is fixed with a piezoelectric actuator 50 coupled (in an embodiment not shown, a hydraulic coupling is possible). This is a layered column of a plurality of individual piezo elements. That of the valve needle 46 opposite end of the piezoelectric actuator 50 is with a housing 52 of the injector is jammed. The piezo actuator 50 is via control lines 54 with the power amplifier 35 connected. About this is the piezoelectric actuator 50 , in still to be displayed manner, for a movement of the piezoelectric actuator 50 supplied required driving energy.

In order to realize an injection, the piezoelectric actuator becomes 50 supplied an electric current. This causes the piezoelectric actuator 50 lengthened in the longitudinal direction. This will cause the valve needle 46 from its valve seat on the valve body 42 lifted, leaving the valve needle 46 in their in 2 shown open state passes. A certain current flow during a certain period of time, which is equivalent to a certain charge, leads to a specific stroke of the valve needle 46 , This stroke retains the valve needle 46 even after the specified period of time has ended and therefore no current flow is left. If the injection is to be ended, then the piezoelectric actuator 50 discharged. For this purpose, a corresponding discharge current is supplied, so that the piezoelectric actuator 50 again takes its initial length and the valve needle 46 comes into contact with its valve seat.

The stroke of the piezo actuator 50 However, when it is fed with electricity, it depends not only on the magnitude of the current, but also on various other quantities. These variables influence the operating behavior of the piezoelectric actuator 50 and are therefore also called "influencing variables". Such an influencing variable is, for example, the temperature of the piezoelectric actuator 50 , the age of the piezo actuator 50 , the number of strokes, which the piezoelectric actuator 50 has already carried out in the course of his life, and also the manufacturing tolerance with which the piezoelectric actuator 50 was produced. Due to different conditions in the production of the piezoelectric actuator 50 In fact, it may happen that identical piezo actuators perform different strokes per se with the same drive energy and the same environmental conditions.

The manufacturing tolerances are an influencing factor, which is systemic and not currently. can be prevented. Not only the manufacturing tolerances of the piezoelectric actuator play a role here 50 but the entire injector 26 a role. Nevertheless, the injector 26 in the combustion chamber 20 To be able to adjust the injected fuel quantity as precisely as possible is the injector 26 before going into the internal combustion engine 10 is used, measured. In particular, the lift behavior is detected as a function of the charge, this property is assigned to a class and this class is converted into a code converted, for example, on the case 52 of the injector 26 is applied. The code will turn from a stuck to the internal combustion engine 10 arranged reading device read out which signals to the control and regulating device 34 passes.

In the control unit 34 is a standard curve 56 (see 3 ), which is a charge Q of a piezoelectric actuator 50 h with his hub in a relationship. This relationship is a straight line, but other, more complex relationships are possible. The standard curve 56 applies to a theoretical ideal case. In reality, however, the curves deviate from the standard curve due to existing manufacturing tolerances 56 from. Corresponding real curves are in 3 With 58 as well as with 60 designated. The location of the real curves 58 respectively 60 opposite the standard curve 56 is in the form of a factor and an offset by the on the injector 26 existing code specified.

The physical meaning of the ratio of the real curve 58 opposite the standard curve 56 will now be with reference to the 4 and 5 using the example of a main injection during a work cycle 62 and a subsequent post-injection 64 explained. In 4 is a desired stroke of the piezoelectric actuator 50 recorded over time. It can be seen that the stroke h2 during a post-injection 64 only about half the size of hub h1 in a main injection 62 ,

How out 3 and from 5 would be apparent using the standard curve 56 a charge Q1 'on the piezoelectric actuator 50 be applied to achieve the desired stroke h1. Due to manufacturing tolerances, however, the charge Q1 actually to be applied for the stroke h1 is significantly lower, namely the correction value K1. To the at a post-injection 64 desired stroke h2 of the piezoelectric actuator 50 To realize this, a charge Q2 must be applied to this, which is from the curve 58 in 3 results. Would the standard curve here too 56 applied, this would lead to a charge Q2 ', which would be too large by the correction value K2. In other words, using the standard curve 56 would be the actually realized stroke of the piezoelectric actuator 50 greater than desired.

In previous methods, regardless of the actual desired stroke h, the charge Q is corrected by a fixed value, namely by that value which applies at the maximum stroke h1 (in the present case, by the correction value K1). This would, as in 5 through the dashed curve 66 is indicated in which at the post-injection 64 desired stroke h2 lead to too low a charge and subsequently to a stroke which is less than the desired stroke h2. To prevent this, the in 1 illustrated internal combustion engine 10 according to the in 6 proceeded procedure. In this procedure, for each single injection within a working cycle according to the factor and the offset made by the on the injector 26 existing code to be specified from the standard curve 56 the charge obtained has been corrected so that the charges required to obtain the desired lift (values Q1 and Q2 in 5 ) are actually achieved. It should be noted that the in 6 For example, the method shown not only for a main injection and a post-injection 62 and 64 , but additionally for a pre-injection 67 is shown.

In 68a an injection time for a pilot injection is specified. In 68b is analogous to an injection time for the main injection, in 68c the injection time for the post-injection specified. By means of a characteristic curve 70 For each individual injection, a desired needle stroke h0, h1, or h2 is determined individually. The corresponding function blocks are in 6 the reference numerals 72a . 72b respectively 72c , In addition, the desired strokes h0 to h2 can also be calculated taking into consideration a fuel quantity to be injected during the injection and / or a fuel pressure present during the injection and / or a temperature of the injector present during the injection 26 be determined.

In a computational block 74 is determined by the standard curve 56 from 3 the respective desired stroke h0, h1 and h2 are converted into a corresponding standard charge Q0 ', Q1' or Q2 '. The corresponding function blocks are in 6 With 76a . 76b respectively 76c designated. These are now in 78a . 78b respectively 78c multiplied by a correction factor F, and in 80a . 80b . 80c an offset OF is added. The factor F and the offset OF form a property-specific correction function and result from that on the injector 26 applied code. This yields corrected charges K0, K1 and K2 corrected charges Q0, Q1 and Q2, respectively. The corresponding function blocks are in 6 but not shown. In 82a . 82b respectively 82c a division takes place by a loading time, which in the blocks 84a . 84b respectively 84c provided. The charging time results from different boundary conditions and can be the same or different for all three injections.

The result is a desired charging current I0, I1 or I2, corresponding to the blocks 86a . 86b respectively 86c , These currents I0, I1 and I2 must for the respective individual injections the piezoelectric actuator 50 be forwarded in the sense of a feedforward control in order to realize the desired strokes h0, h1 and h2 with high precision. For each individual injection within a working cycle, an individually corrected charge is thus set by means of injection-specific current parameters.

For determining the discharge currents which are used to terminate an injection from the piezoelectric actuator 50 must be dissipated, the procedure is analogous. It should also be noted that as an alternative to the in 6 shown characteristic 70 the stroke h of the valve needle 46 or the piezoelectric actuator 50 can also be calculated by means of a factor and an offset from a load time.

Claims (9)

Method for operating an internal combustion engine ( 10 ), in which fuel via a fuel injection device ( 26 ), which is a capacitive actuator ( 50 ) into a combustion chamber ( 20 ) of the internal combustion engine ( 10 ), in which a production-specific property of the fuel injection device ( 26 ) is identified, in which at least one for a desired first stroke (h1) of the capacitive actuating element ( 50 ) and in which the standard charge (Q1 ') is supplied with a correction value (K1) obtained in consideration of a property-specific correction function (F, OF) and the first desired stroke (h1) , characterized in that one for a desired second stroke (h2) of the capacitive actuating element ( 50 ) and this second standard charge (Q2 ') is supplied with a correction value (K2) which is obtained in consideration of the property-specific correction function (F, OF) and the second stroke (h2). A method according to claim 1, characterized in that within a working cycle different strokes ( 62 . 64 . 67 ) and that for each desired stroke ( 62 . 64 . 67 ) the respectively required standard charge (Q0 ', Q1', Q2 ') is determined and the standard charge (Q0', Q1 ', Q2') is supplied with a correction value (K0, K1, K2) which, taking into account the property-specific correction function (F , OF) and the respective desired stroke (h0, h1, h2) is obtained. Method according to one of claims 1 or 2, characterized in that the desired stroke (h0, h1, h2) of an injection ( 62 . 64 . 67 ) taking into account a desired injection time ( 68a . 68b . 68c ) and one at the injection ( 62 . 64 . 67 ) fuel quantity to be injected and / or a fuel pressure present during the injection and / or a temperature of the fuel injection device present during the injection is obtained. Method according to one of the preceding claims, characterized in that the application of the correction value (K0, K1, K2) takes place in that the standard charge (Q0 ', Q1', Q2 ') is multiplied by a factor (F) ( 78 ) and an offset (OF) is added to the product ( 80 ). Method according to one of the preceding claims, characterized in that a current (I0, I1, I2), with which the capacitive element ( 50 ) is to be fed from the quotient ( 82 ) of the corrected standard charge (Q0 ', Q1', Q2 ') and a charging time ( 841 . 84b . 84c ) is determined. Computer program, characterized in that it is programmed for use in a method according to one of the preceding claims. Electrical storage medium for a control and / or regulating device ( 34 ) an internal combustion engine ( 10 ), characterized in that on it a computer program for use in a method of claims 1 to 5 is stored. Control and / or regulating device ( 34 ) for an internal combustion engine ( 10 ), characterized in that it is programmed for use in a method according to one of claims 1 to 5. Internal combustion engine ( 10 ), in particular for a motor vehicle, with a control and / or regulating device ( 34 ), characterized in that the control and / or regulating device ( 34 ) is programmed for use in a method according to one of claims 1 to 5.

Images