EP2699783A1

EP2699783A1 - Method and device for calibrating a fuel metering system of a motor vehicle

Info

Publication number: EP2699783A1
Application number: EP12709871.3A
Authority: EP
Inventors: Michael Walter; Stefan Bollinger
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2011-04-18
Filing date: 2012-03-16
Publication date: 2014-02-26
Anticipated expiration: 2032-03-16
Also published as: CN103492693A; KR101858295B1; DE102011007563A1; EP2699783B1; KR20140024324A; WO2012143187A1; CN103492693B

Abstract

The present invention relates to a 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 duration and a second injector is actuated with a second test injection with a second actuation duration, and a resulting overall excitation is detected as a superposition of a first excitation of the first injector and a second excitation of the second injector, wherein from said overall excitation there is determined an overall vibration from which the first excitation of the first injector and the second excitation of the second injector are reconstructed, and on the basis of the respective excitation as a respective quantity signal, a zero quantity calibration is performed for the respective injector independently of the other injector, whereby a respective minimum actuation duration for a respective injector is determined. A corresponding device is also provided.

Description

Description title

Method and device for calibrating a fuel metering system of a motor vehicle

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. If a partial injection completely disappears, for example because an existing injection component, in the case of common-rail injection systems, an injector does not yet inject due to customary tolerances for an underlying control signal, this has considerable effects on the operation of the internal combustion engine. expressed by increased noise during combustion. An essential The tolerance source for the quantity accuracy of the pre-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, ie. 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 described, for example, in the document DE 199 45 618 A1. 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 period then present corresponds to an operating state in which the injection for the respective internal combustion engine, d. H. the cylinder of the

Internal combustion engine just starts. 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 DE 10 2008 002 482 A1 a method and a device for calibrating a Kraftstoffzumesssystems an internal combustion engine is also known, in which at least one injector with a first test injection with a first

Test injection quantity is controlled and thereby 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 quantity second injection quantity and thereby resulting at least second quantity signal is detected, to this at least second injection quantity is determined at least a second Mindestansteuerdauer. 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. 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 procedure 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 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. Each test injection of the two injectors results in excitation 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 then takes place autonomously for each injector 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 or 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, wherein T is not a multiple of 90 °.

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

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

Figure 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.

Figure 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 drive characteristic map of a first injector, which has been calibrated in parallel with a second injector according to a further embodiment of the method according to the invention, the drive duration of the second injector being taken as a parameter here.

FIG. 4 shows, in a graphic illustration, a superimposition of two amplitude signals of two injectors which lie relative to one another in such a way that they enclose 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.

FIG. 1 shows, as part of an embodiment of the method according to the invention, a reconstruction of excitations of two injectors loaded simultaneously with 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. The measured excitation or oscillation results as a superimposition of oscillations, excited by the respective individual two injectors loaded with respective test injections.

In 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

Vibration 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: A1 = A12 ^■ sin (<x)

A2 = A12 ^■ cos (a) where

A12 is the amplitude of the total vibration d. H. the superimposition of the two oscillations caused by the respective injectors is A1, 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 each 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 shows a test result which was obtained on a motor vehicle with a 4-cylinder engine after carrying out 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 actuation duration of a first injector 1 was used as a parameter and took in each case the activation duration 140 με,

180 με and 220 με. 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 με, registered. In this case, the drive duration characteristic map 10 represents the drive duration detection field of the second injector 2, with a drive duration of the first injector of 140 με. The control duration characteristic map 20 was recorded at a drive duration of the first injector of 180 με and the drive duration characteristic field 30 was recorded for a drive duration of the first injector of 220 με. The three determined control duration maps of the second injector 2 are exactly within the measurement accuracy of the speed evaluation used. FIG. 3 shows a corresponding diagram for corresponding activation duration maps of the first injector 1, in which case quasi 2 injector 1 and injector 2 have their roles "exchanged". In the graph shown here, a respective specific quantity signal S1 of the first injector

1 over the control period T, measured in με, applied. The actuation duration of the second injector 2 was used as a parameter and was for Ansteuerdauerkennfeld 10 '140 με, for Ansteuerdauerkennfeld 20' 180 με and for Ansteuerdauerkennfeld 30 '220 με. 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 injectors or cylinders arranged in antiphase. 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 if an absolute value of the respective injection for which the adjustment is made is not relevant.

FIG. 4 now shows a reconstruction according to the method according to the invention of vibrations excited by a first injector and a second injector from a total vibration resulting from the two oscillations. The injectors 1 and 2 enclose an angle τ which is not equal to a multiple of 90 °. Corresponding to Figure 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 is analogous to the reconstruction in FIG. 1. This results in a generalized evaluation relationship as follows:

A1 = A12 ^■ sin (a) / sin (180 ° -τ) A2 = A12 ^■ sin (τ-a) / sin (180 ° -τ)

FIG. 5 shows a simplified block diagram of an embodiment of a device according to the invention 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 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 with a first drive duration by means of drive pulse 35_1 and for driving a second injector with a second test injection with 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

claims

1. A 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 overall excitation as a superposition of a first excitation of the first injector and a second excitation of 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 on the basis of the respective excitation as a respective quantity signal for the zero-point calibration is carried out independently of the other injector, whereby a respective minimum drive duration is determined for a respective injector.

2. 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.

3. 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.

4. The method of claim 1, 2 or 3, wherein the first injector and the second injector are mutually orthogonal.

5. The method of claim 1, 2 or 3, wherein the first injector and the second injector are in opposite phase to each other. The method of claim 1, 2 or 3, wherein the first injector and the second injector are to each other so that they include an angle τ, with τ ΐ η - 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.

Apparatus for calibrating a fuel metering system of an internal combustion engine, in particular of a motor vehicle, with 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, with sensor means for detecting a resulting total excitation as a superposition of a first excitation of the first injector and a second excitation of the second injector and for determining a resulting total vibration, and with computation means configured to receive from the total vibration the first excitation of the first injector and the second excitation of the second injector reconstruct, and perform based on the respective excitation as a respective quantity signal for the respective injector independently of the other injector, a zero quantity calibration, whereby for a respective injector a respective Mi is to be determined.

Apparatus according to claim 8, in particular for use in a common rail injection system.