DE102011007563A1 - Method and device for calibrating a fuel metering system of a motor vehicle - Google Patents

Abstract

The present invention relates to a method for calibrating a fuel metering system of an internal combustion engine, in particular a motor vehicle, in which a first injector is activated with a first test injection with a first control duration and a second injector with a second test injection with a second control duration and a resulting overall excitation is detected as a superposition of a first excitation caused by the first injector and a second excitation caused by the second injector, an overall oscillation being determined from this, from which the first excitation of the first injector and the second excitation of the second injector are reconstructed, and on the basis the respective excitation as a respective quantity signal for the respective injector, a zero quantity calibration is carried out independently of the other injector, as a result of which a respective minimum activation duration is determined for a respective injector. A corresponding device is also provided.

Description

The invention relates to a method and a device for calibrating a fuel metering system of an internal combustion engine, in particular of a motor vehicle.

State of the art

In modern fuel injection systems of the type concerned here, such as in common-rail diesel injection systems, carried out to improve a mixture preparation at the same time before or after a corresponding main injection partial injections with relatively small amounts of fuel. The said main injection is calculated as a rule on the basis of a torque request of a corresponding driver. The injection quantities of said partial injections should be as low as possible in order to avoid emission disadvantages. On the other hand, the injection quantities must be large enough so that, taking into account all tolerance sources, the minimum quantity necessary for the corresponding combustion process is always emitted. Such improved mixture preparation allows reduced exhaust emissions and reduced combustion noise.

The small amounts of fuel in the part injections mentioned require a precise metering of the respective injection quantities. Falls a partial injection completely away, for example, because a present injection component, injectors in common-rail injection systems, due to conventional tolerances at an underlying drive signal is not yet injected, this has a significant impact on the operation of the engine, which, for example, by increased Noise during combustion manifests. An essential source of tolerance for the quantity accuracy of the pilot injection is a so-called drift of the respective injector.

In the aforementioned common-rail diesel injection systems, pressure generation and injection are decoupled from one another by means of a high-pressure accumulator, wherein the injection pressure is generated independently of the engine speed and the injection quantity and is available for injection in the high-pressure accumulator. The respective injection time and the respective injection quantity are calculated in an electronic engine control unit and added by the respective injectors of each cylinder of the internal combustion engine via remote-controlled valves. It has to be ensured that the said partial injections are always realized with the highest possible precision.

When manufacturing injectors of a corresponding fuel metering system occurring manufacturing tolerances cause differences in the operating characteristics of the individual injectors, which often occur only over the life of the respective injectors or the fuel metering system or even enhanced during the lifetime. In addition, the injectors of a fuel metering system usually have different quantity maps, d. H. different dependencies between injection quantities, rail pressure and activation duration. As a result, the various injectors fill the combustion chamber with different amounts of fuel, even with very precise control.

A metering of said minimum amounts is based on a so-called zero-quantity calibration. This is, for example, in the publication DE 199 45 618 A1 described. In the overrun operation of the respective internal combustion engine, a single injector is activated and the actuation period is increased stepwise until a change in a quantity substitute signal (short: quantity signal) occurs at a minimum actuation time, for example a torque increase measurable on the internal combustion engine, on the basis of which now that an injection or injection has taken place. The control duration then present corresponds to an operating state in which the injection for the relevant internal combustion engine, ie the cylinder of the internal combustion engine, is being used. This procedure is carried out accordingly with respect to all injectors or cylinders of the internal combustion engine. The control periods thus obtained are stored in a so-called control map, which is used in a subsequent control of the injectors in the context of a zero-quantity calibration, wherein a current value of the control period is respectively converted into a correction value for the amount of fuel to be supplied.

From the DE 10 2008 002 482 A1 Furthermore, a method and a device for calibrating a fuel metering system of an internal combustion engine is known in which at least one injector with a first test injection is activated with a first test injection quantity and a resulting resulting first quantity signal is detected. In this case, a first Mindestansteuerdauer is determined and it is further provided that the at least one injector with at least one second test injection is controlled with a deviating from the first injection amount second injection quantity and thereby resulting at least second quantity signal is detected, wherein at least this second injection quantity an at least second Mindestansteuerdauer is determined .. Based on the first Mindestansteuerdauer and the At least second Mindestansteuerdauer and the first quantity signal and the at least second quantity signal then a regression calculation is performed. With the aid of the method presented therein, the zero-rate calibration learning process can be improved by reducing the time required to learn a calibration value.

Disclosure of the invention

In the zero-quantity calibration already mentioned above, test injections with variable actuation duration are carried out in the thrust on a cylinder or the injector associated therewith. For each activation period, the associated quantity replacement signal, which can be obtained, for example, by processing the measured speed signal, is calculated. The control period is varied so long until a predetermined setpoint of the quantity signal is reached. In a subsequent step, a drive duration learning value is calculated and stored non-volatile. The method is used individually for each injector at several rail pressure levels.

The calibration of the individual injectors at the individual rail pressure stages is therefore sequential.

An object of the present invention was now to accelerate the determination of the above learning values.

This object is achieved by a method according to the independent patent claim 1 and a corresponding device according to the independent claim 8. Advantageous embodiments are formulated in the respective subclaims.

According to the method of the invention, a first injector with a first test injection and a first activation duration and a second injector with a second test injection and a second activation duration are provided for calibrating a fuel metering system of an internal combustion engine, in particular a motor vehicle, and a resulting overall excitation as a superimposition of a first injector excitation caused by the first test injection of the first injector, hereinafter referred to as the first excitation caused by the first injector, first excitation or first excitation of the first injector, and a second excitation caused by the second test injection of the second injector, hereinafter referred to as second by the second injector caused excitation, second excitation or second excitation of the second injector referred capture. From this, a total vibration is then determined, from which the first excitation of the first injector and the second excitation of the second injector are reconstructed. On the basis of the respective excitation as a respective quantity signal for the respective injector, a zero quantity calibration is then carried out independently of the other injector, whereby a respective minimum actuation duration is determined for a respective injector.

The learning values are determined as in the normal zero-quantity calibration in the thrust. However, the proposed method with respect to the learning process is carried out independently on two injectors in parallel. From each test injection of the two injectors results in a stimulation of the drive train. These suggestions, as parallel or approximately at the same time, are superimposed on the drive train. A corresponding speed signal evaluation determines a total vibration with magnitude and phase. From this, the excitations produced by the respective individual injectors can then be reconstructed according to the principle of vector addition. On the basis of the quantity signal reconstructed for the respective injector, a calibration for each injector then takes place independently as in the case of a previously mentioned "normal" zero-quantity calibration.

Advantage of the proposed method is the ability to double the calibration without having to accept a deterioration in the signal-to-noise ratio in purchasing.

According to one embodiment of the proposed method, the first test injection for the first injector and the second test injection for the second injector are made in the thrust and in approximately the same time. This means that a first cylinder assigned to the first injector and a second cylinder assigned to the second injector are subjected to test injections approximately at the same time.

According to one possible embodiment of the proposed method, the first injector or the first cylinder assigned to it and the second injector or the second cylinder assigned to it are mutually orthogonal. That is, in the present disclosure, that in this embodiment, the first cylinder and the second cylinder are arranged to each other such that the vibrations excited by the respective cylinders are phase-shifted by 90 ° with respect to the corresponding camshaft frequency. In a corresponding pointer representation, ie a vectorial representation in the complex plane, then the two vectors of the vibrations excited by the two cylinders are mutually orthogonal. This is typically the case with four-cylinder in-line engines. On the corresponding camshaft, which is driven by a corresponding crankshaft in the ratio 2: 1 (ie the camshaft rotates half as fast as the crankshaft) can be seen this orthogonality well. In a four-cylinder engine, the camshaft has eight cams, with each cylinder associated with an intake valve cam and an exhaust valve cam. Intake valve cams and exhaust valve cams are alternately disposed on the camshaft so that all intake valve cams are orthogonal to each other.

Alternatively, the first injector and the second injector or the respectively associated first and second cylinders can also be in opposite phase to one another, ie. H. the vibrations excited by the respective cylinders are phase-shifted by 180 ° with respect to the corresponding camshaft frequency. According to yet another embodiment, the first and second cylinders are mutually adjacent to each other at an angle τ, where τ is not equal to a multiple of 90 ° and corresponds to the phase shift between the oscillations respectively excited by the cylinders with respect to the corresponding camshaft frequency.

Furthermore, it can be provided that the determined respective excitations are entered as respective quantity signals for a respective injector in a respective drive duration map and stored in this.

When carrying out the method according to the invention, two cylinders are simultaneously subjected to respective test injections by correspondingly assigned injectors during thrust. Each of these test injections excites the vibratory components of the powertrain. The resulting superposition of these two excited vibrations can be measured by means of a speed sensor. In accordance with the method according to the invention, the amplitudes of the individual signals belonging to the respective injectors are then reconstructed from the superimposed signal.

The invention further relates to a device for calibrating a Kraftstoffzumesssystems an internal combustion engine, in particular a motor vehicle. The device comprises control means for driving a first injector with a first test injection having a first drive duration and a second injector with a second test injection having a second drive duration. Furthermore, sensor means are provided, which are configured to detect a resulting total excitation as a superposition of a first excitation caused by the first injector and a second excitation effected by the second injector and to determine a resulting overall oscillation. Furthermore, the proposed device comprises computing means which are configured to reconstruct from the overall vibration the first excitation of the first injector and the second excitation of the second injector. Furthermore, a zero quantity calibration can be carried out independently of the other injector on the basis of a respective excitation as a respective quantity signal for a respective injector, whereby a respective minimum actuation duration can be determined for a respective injector.

The proposed device can be used in particular in a common rail diesel injection system.

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the respectively indicated combination but also in other combinations or alone, without departing from the scope of the present invention.

Brief description of the drawings

1 shows a graphical representation of the example of a 4-cylinder system of a superposition of amplitude signals of two orthogonal injectors or cylinders and their carried out according to an embodiment of the method separation into respective individual amplitude signals of the two individual injectors.

2 shows a Ansteuerdauerkennfeld a second injector which has been calibrated in parallel with a first injector according to a further embodiment of the method according to the invention, wherein the drive duration of the first injector received as a parameter.

3 shows a Ansteuerdauerkennfeld a first injector, which was calibrated in parallel with a second injector according to a further embodiment of the method according to the invention, in which case the drive duration of the second injector received as a parameter.

4 shows a graphical representation of a superposition of two amplitude signals of two injectors, which lie to each other so that they include an angle τ, which is not equal to a multiple of 90 °.

5 shows an overview block diagram of an embodiment of a device according to the invention.

In 1 As part of an embodiment of the method according to the invention, a reconstruction of excitations caused by two cylinders acted upon at the same time by respective test injections is shown from a measured excitation of oscillatable components of the drive train within an internal combustion engine, in particular of a motor vehicle. The measured excitation or oscillation results here as a superimposition of oscillations, excited by the two cylinders acted upon by respective test injections or by two injectors respectively assigned corresponding to the two cylinders and driven by the respective test injections.

In the present case, it is now assumed using the example of a 4-cylinder system that the two injectors controlled with respective test injections or the correspondingly assigned cylinders are orthogonal to one another. Orthogonal in the context of the present disclosure means that the two cylinders of the corresponding engine are arranged such that the cylinders or the respectively excited by them oscillations, with respect to the corresponding camshaft frequency, are phase-shifted by 90 °. In a pointer representation, which is a vector representation in the complex plane, as in 1 Accordingly, the two vectors of the vibrations excited by the two cylinders are orthogonal to one another. This is the case, for example, in four-cylinder in-line engines. Accordingly, the first injector or the associated cylinder 1 is characterized by the ordinate, while the second injector or the associated cylinder 2 is represented by the abscissa. The now measured oscillation is first represented by an amplitude A12 and a corresponding phase α. This can be done, for example, as a Fourier transformation of a corresponding speed signal. The respective phases of a pure excitation or oscillation on the first cylinder 1 or the second cylinder 2 are determined in an initial configuration of the cylinder system and henceforth define a corresponding coordinate reference system, ie they are, as already mentioned above, used as axes in the coordinate system shown here , The measured signal with amplitude A12 and phase α is then projected on the two axes according to trigonometric standard. This is then as follows: A1 = A12 × sin (α) A2 = A12 · cos (α) in which

A12 is the amplitude of the total vibration, ie the superimposition of the two oscillations caused by the respective injectors, A1 is the reconstructed amplitude of cylinder 1 and A2 represents the reconstructed amplitude of cylinder 2. α results from the phase or phase shift of the measured excitation with respect to the phase of cylinder 2 or cylinder 1.

As a result, the two individual excitations causing the total excitation, which are caused by the injectors 1 and 2, can be separated in a simple manner.

Then, a search algorithm according to the prior art is performed for each of the two injectors, the first injector 1 and the second injector 2, wherein a drive duration of a respective injector is tracked until a predetermined target amount is reached and then it becomes a above-mentioned Learning value determined according to the prior art.

2 is a test result again, which was obtained on a motor vehicle with a 4-cylinder engine after performing the method according to the invention. In this case, a received drive characteristic map of a second injector 2 was determined three times. The respective activation duration of a first injector 1 was used as a parameter and assumed in each case the activation duration 140 μs, 180 μs and 220 μs. The three determined drive characteristic curves 10 . 20 . 30 are here in a graph showing a respective specific quantity signal S2 of the second injector 2 over the control period T, measured in μs, registered. In this case, the Ansteuerdauerkennfeld 10 the Ansteuerdauerkennfeld of the second injector 2, at a drive time of the first injector of 140 microseconds. The drive duration map 20 was recorded at a drive time of the first injector of 180 μs and the Ansteuerdauerkennfeld 30 was recorded for a drive duration of the first injector of 220 μs. The three determined control duration maps of the second injector 2 are exactly in the context of the measurement accuracy of the speed evaluation used.

In 3 a corresponding graph for corresponding control duration maps of the first injector 1 is shown, here almost opposite 2 Injector 1 and injector 2 have their roles "swapped". In the diagram shown here, a respective specific quantity signal S1 of the first injector 1 was plotted over the activation duration T, measured in μs. The activation duration of the second injector 2 was used as a parameter and amounted to the drive duration characteristic field 10 ' 140 μs, for actuation characteristic map 20 ' 180 μs and for driving duration map 30 ' 220 μs. Again, the three Ansteuerdauerkennfelder determined for injector 1 in the measurement accuracy of the Drehzahlauswertverfahrens exactly to each other.

As an alternative to the mentioned scenario, in which two orthogonal injectors 1 and 2 or respective cylinders are subjected to respective test injections, it is also possible to excite two out-of-phase injectors or cylinders, which means that the respective excited oscillations are 180 ° relative to the corresponding camshaft frequency ° out of phase with each other. The two oscillations extinguish exactly when the injection quantities for the respective injectors are the same size. This can be used, for example, to exactly match two injectors when an absolute value of the respective injection for which the adjustment is made is not relevant

4 Now shows a made according to the method of the invention reconstruction of each of a first injector and a second injector excited vibrations from a result of the two oscillations and measured total vibration. The injectors 1 and 2 enclose an angle τ which is not equal to a multiple of 90 °. As already explained above, this means that the vibrations excited by the injectors 1 and 2 or by the two cylinders respectively assigned to them, relative to the corresponding camshaft frequency, are phase-shifted relative to one another by τ. Correspondingly too 1 This constellation is also shown in a coordinate system, wherein the second cylinder 2 and injector 2 on a horizontal axis and the first cylinder 1 and injector 1 is marked on a relative to the horizontal axis rotated by τ axis. The coordinate axes of this coordinate system therefore include an angle τ. The measured signal is in turn converted into a representation with amplitude and phase and drawn accordingly in this coordinate system. In this case, the amplitude A12 is entered at an angle α to the injector 2. A reconstruction of the individual amplitudes A1 and A2 results here by applying the sine theorem analogous to the reconstruction in FIG 1 , This results in a generalized evaluation relationship as follows: A1 = A12 × sin (α) / sin (180 ° -τ) A2 = A12 × sin (τ-α) / sin (180 ° -τ)

5 shows a simplified block diagram of an embodiment of an inventive device for controlling a fuel metering system. Shown is an internal combustion engine 10 coming from a fuel metering unit 30 gets a certain amount of fuel at a certain time. Here are sensor means in the form of various sensors 40 , In particular a speed sensor, available, the measured values 15 capture the operating state of the internal combustion engine 10 characterize this and corresponding to a control unit 20 hand off. The control unit 20 Beyond that are output signals 25 other existing sensors 45 supplied, the quantities detect the condition of the fuel metering unit 30 and / or environmental conditions. Such a size 25 is, for example, a given driver's request. For the other sizes 25 may, for example, also be the pressure and temperature of the ambient air. The control unit 20 calculated from the measured values 15 and the other sizes 25 drive pulses 35 with which the fuel metering unit 30 is charged.

The internal combustion engine is preferably a direct injection and / or a self-igniting internal combustion engine.

The fuel metering unit 30 can be configured differently. It may, for example, be designed as a previously mentioned and described common rail injection system. In such a system, a high pressure pump compresses fuel in a reservoir. From this memory then the fuel passes through injectors into respective combustion chambers of the internal combustion engine. The duration and / or the beginning of the fuel injection is controlled by the injectors. The injectors preferably each include a solenoid valve or a piezoelectric actuator.

Per cylinder, an electrically actuated valve is provided in each case. In the following, the solenoid valve and / or the piezoelectric actuator, which affects the fuel metering is referred to as an electrically actuable valve.

An electrically operable valve is arranged so that an amount of fuel to be injected is determined by opening time or by closing time of the valve.

The control unit is now equipped to calibrate the fuel metering system 20 according to the invention via control means 50 for controlling a first injector with a first test injection with a first activation duration by means of a drive pulse 35_1 and for driving a second injector with a second test injection with a second drive time by means of a drive pulse 35_2 , Further, the sensors 40 , in particular a provided speed sensor, configured to detect a total excitation resulting therefrom as a superposition of a first excitation caused by the first injector and a second excitation effected by the second injector and to determine a resulting overall vibration. The control unit 20 also has computational resources 55 that are configured from the Total vibration to reconstruct the first excitation of the first injector and the second excitation of the second injector and based on the respective suggestions as a respective quantity signal for the respective injector independent of the other injector perform a zero-quantity calibration. As a result, a respective minimum activation duration is determined for a respective injector.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 19945618 A1 [0006]
• DE 102008002482 A1 [0007]

Claims (9)

Method for calibrating a fuel metering system of an internal combustion engine, in particular of a motor vehicle, in which a first injector with a first test injection with a first drive time and a second injector with a second test injection with a second drive time is driven and a resulting total excitation as a superposition of a first through the first injector caused stimulus and a second excitation caused by the second injector is detected, from which a total vibration is determined, from which the first excitation of the first injector and the second excitation of the second injector are reconstructed, and based on the respective excitation as respective Quantity signal for the respective injector, regardless of the other injector a zero quantity calibration is performed, whereby for each injector a respective Mindestansteuerdauer is determined. The method of claim 1, wherein the total vibration is determined with an amount and a phase, from which by applying vector addition, the first excitation of the first injector and the second excitation of the second injector are reconstructed. The method of claim 1 or 2, wherein the first test injection for the first injector and the second test injection for the second injector are made in the thrust and at about the same time. The method of claim 1, 2 or 3, wherein the first excitation and the second excitation are phase-shifted with respect to a respective camshaft frequency by 90 ° to each other. The method of claim 1, 2 or 3, wherein the first excitation and the second excitation relative to a respective camshaft frequency are in opposite phase to each other. The method of claim 1, 2 or 3, wherein the first excitation and the second excitation are phase-shifted with respect to each other at a respective camshaft frequency, with τ ≠ n · 90 °, n = 0, 1, 2, .... Method according to one of the preceding claims, wherein the determined respective excitations are registered as respective quantity signals for a respective injector in a respective Ansteuerdauerkennfeld and stored in this. Device for calibrating a fuel metering system of an internal combustion engine ( 10 ) in particular of a motor vehicle, with control means ( 50 ) for controlling a first injector having a first test injection with a first activation duration and a second injector having a second test injection having a second activation duration, with sensor means ( 40 ) for detecting a resulting total excitation as a superposition of a first excitation caused by the first injector and a second excitation effected by the second injector and for determining a total vibration resulting therefrom, and 55 ) configured to reconstruct from the overall vibration the first excitation of the first injector and the second excitation of the second injector, and zero calibrate independently of the other injector based on the respective excitation as a respective quantity signal for the respective injector each injector a respective Mindestansteuerdauer is to be determined. Apparatus according to claim 8, in particular for use in a common rail injection system.

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