EP2699783B1 - Method and device for calibrating a fuel metering system of a motor vehicle - Google Patents

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 one The tolerance source 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 are even enhanced during the life. 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 approach will apply to all Injectors or cylinders of the internal combustion engine carried out accordingly. 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 injection 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 set signal and the at least second set 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. The DE 103 59 306 A1 discloses another method for calibrating a fuel metering system of an internal combustion engine.

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 claim 1 and a corresponding device according to the independent claim 6. 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 Detecting excitation of the first injector and a second excitation of the second injector. 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 excitation of 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.

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.

Alternatively, the first injector and the second injector and the respective cylinders may also be in opposite phase to each other or according to yet another embodiment also to each other so that they include an angle τ, where τ is not equal to a multiple of 90 °.

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 injectors are simultaneously subjected to respective test injections 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. Further Sensor means are provided which are configured to detect a resulting total excitation as a superposition of a first excitation of the first injector and a second excitation of the second injector and to determine a resulting overall vibration. 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 particular combination indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

Brief description of the drawings

FIG. 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.

FIG. 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.

FIG. 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.

FIG. 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 °.

FIG. 5

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

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

$$\mathrm{A}2=\mathrm{A}\mathrm{12}\cdot \cos \left(\mathrm{\alpha }\right)$$

wobeiIn the present case, it is now assumed using the example of a 4-cylinder system that the two injectors loaded with respective test injections or the correspondingly assigned cylinders are orthogonal to one another. Accordingly, the first injector or the associated cylinder 1 is characterized by the ordinate, while the second injector or 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 known from the prior art and 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: $$\mathrm{A}\mathrm{1}=\mathrm{A}\mathrm{12}\cdot \sin \left(\mathrm{\alpha }\right)$$

$$\mathrm{A}2=\mathrm{A}\mathrm{12}\cdot \cos \left(\mathrm{\alpha }\right)$$

in which

A12 is the amplitude of the total vibration d. H. the superposition 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 of the injectors 1 and 2 causing the overall excitation 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.

FIG. 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 duty curves 10, 20, 30 are in this case in a graph showing a respective specific quantity signal S2 of the second injector 1 over the drive time T, measured in μs, registered. Here, the Ansteuerdauerkennfeld 10 represents the Ansteuerdauerkennfeld 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 duration of the first injector of 180 .mu.s, and the drive duration map 30 was recorded for a drive duration of the first injector of 220 .mu.s. The three determined control duration maps of the second injector 2 are exactly within the measurement accuracy of the speed evaluation used.

In FIG. 3 a corresponding graph for corresponding control duration maps of the first injector 1 is shown, here almost opposite FIG. 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 drive duration of the second injector 2 was used as a parameter and amounted to drive actuation characteristic 10 '140 microseconds, for drive duration map 20' 180 microseconds and for Ansteuerdauerkennfeld 30 '220 microseconds. Again, the three Ansteuerdauerkennfelder determined for injector 1 in the measurement accuracy of the Drehzahlauswertverfahrens exactly to each other.

As an alternative to the aforementioned scenario, in which two orthogonal injectors 1 and 2 or corresponding cylinders are subjected to respective test injections, it is also possible to excite two out-of-phase injectors or cylinders. 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.

$$\mathrm{A}2=\mathrm{A}\mathrm{12}\cdot \sin \left(\mathrm{\tau }-\mathrm{\alpha }\right)/\sin \left(180°-\mathrm{\tau }\right)$$

FIG. 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 °. Correspondingly too FIG. 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 application of the sine theorem analogous to the reconstruction in FIG. 1 , This results in a generalized evaluation relationship as follows: $$\mathrm{A}\mathrm{1}=\mathrm{A}\mathrm{12}\cdot \sin \left(\mathrm{\alpha }\right)/\sin \left(180°-\mathrm{\tau }\right)$$

$$\mathrm{A}2=\mathrm{A}\mathrm{12}\cdot \sin \left(\mathrm{\tau }-\mathrm{\alpha }\right)/\sin \left(180°-\mathrm{\tau }\right)$$

FIG. 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, which receives a certain amount of fuel from a Kraftstoffzumesseinheit 30 at a given time. In this case, sensor means in the form of various sensors 40, in particular a rotational speed sensor, are present, which detect measured values 15 which characterize the operating state of the internal combustion engine 10 and forward them accordingly to a control unit 20. The control unit 20, moreover, output signals 25 of other existing sensors 45, which detect quantities that characterize the state of the fuel metering unit 30 and / or environmental conditions. Such a size 25 is, for example, a given driver's request. In the other sizes 25, for example, may also be the pressure and temperature of the ambient air. The control unit 20 calculates, on the basis of the measured values 15 and the further variables 25, control pulses 35 with which the fuel metering unit 30 is acted upon.

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

The fuel metering unit 30 may 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.

For the calibration of the fuel metering system, the control unit 20 according to the invention now has control means 50 for driving a first injector with a first test injection having a first drive duration by means of drive pulse 35_1 and for driving a second injector with a second test injection having a second drive duration by means of drive pulse 35_2. Furthermore, the sensors 40, in particular a provided speed sensor, are configured to detect a total excitation resulting therefrom as a superposition of a first excitation of the first injector and a second excitation of the second injector and to determine a resulting overall vibration. The control unit 20 further has computing means 55 which are configured to reconstruct from the overall vibration the first excitation of the first injector and the second excitation of the second injector and based on the respective excitations as a respective quantity signal for the respective injector independently of the other injector to perform a zero-quantity calibration. As a result, a respective minimum activation duration is determined for a respective injector.

Claims (7)

1. Method for calibrating a fuel metering system of an internal combustion engine, in particular of a motor vehicle, in which a first injector is actuated with a first test injection with a first actuation period and a second injector is actuated with a second test injection with a second actuation period, and a total vibration excitation of the drive train which results therefrom is detected as superimposition of a first excitation of the first injector and a second excitation of the second injector, wherein a total vibration is determined therefrom, from which vibration the first excitation of the first injector and the second excitation of the second injector are reconstructed, and zero quantity calibration is carried out on the basis of the respective excitation as a respective quantity signal for the respective injector independently of the other injector, as a result of which a respective minimum actuation period is determined for a respective injector, wherein the total vibration is determined with an absolute value and a phase, on the basis of which the first excitation of the first injector and the second excitation of the second injector are reconstructed by applying vector addition, wherein the first test injection for the first injector and the second test injection for the second injector are performed in the overrun mode and approximately simultaneously.
2. Method according to Claim 1, wherein the first injector and the second injector are located orthogonally with respect to one another.
3. Method according to Claim 1, wherein the first injector and the second injector are located in antiphase with respect to one another.
4. Method according to Claim 1, wherein the first injector and the second injector are located with respect to one another in such a way that they enclose an angle τ, where τ ≠ n · 90°, n = 0, 1, 2, etc.
5. Method according to one of the preceding claims, wherein the respective determined excitations are input as respective quantity signals for a respective injector into a respective actuation period characteristic diagram and stored therein.
6. Device for calibrating a fuel metering system of an internal combustion engine, in particular of a motor vehicle, with control means for actuating a first injector with a first test injection with a first actuation period and a second injector with a second test injection with a second actuation period, with sensor means for detecting a total vibration excitation of the drive train which results therefrom as a superimposition of a first excitation of the first injector and a second excitation of the second injector, and for determining a total vibration which results therefrom, and with computing means which are configured to reconstruct from the total vibration the first excitation of the first injector and the second excitation of the second injector, and to carry out zero quantity calibration on the basis of the respective excitation as a respective quantity signal for the respective injector independently of the other injector, as a result of which a respective minimum actuation period can be determined for a respective injector, wherein the total vibration is determined with an absolute value and a phase, on the basis of which the first excitation of the first injector and the second excitation of the second injector are reconstructed by applying vector addition, wherein the first test injection for the first injector and the second test injection for the second injector are performed in the overrun mode and approximately simultaneously.
7. Device according to Claim 6, for application in a common rail injection system.

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