DE102005011836B4 - Method and device for controlling an internal combustion engine - Google Patents

Abstract

Method for controlling an internal combustion engine, correction values (QKK) for correcting a quantity (QK) characterizing the quantity of fuel to be injected being determined in certain operating states, wherein the distance (D) between a first partial injection and a second partial injection is changed and the dependence of a manipulated variable (Q) QKL) of a controller (153), which adjusts the speed to a desired value, is determined from the distance (D) of the first and the second partial injection.

Description

State of the art

The invention relates to a method and a device for controlling an internal combustion engine.

Methods and apparatus for controlling an internal combustion engine are known in which the injection process is divided into a plurality of partial injections. In the first partial injection creates a pressure wave in the supply line between an injector and a pressure accumulator. Since the pressure has a direct influence on the injected fuel quantity, this will affect subsequent partial injections. To compensate for this effect, a so-called pressure wave correction takes place. Such a pressure wave correction is, for example, in the DE 197 12 143 A1 described.

The pressure wave correction corrects the influence of the pressure wave on the injection quantity. This is essentially done by determining a correction quantity for the respective operating point and calculating it with the desired spray quantity. The operating point is determined essentially by the distance between the two partial injections. In conventional systems, the correction amounts are determined experimentally on a hydraulic test rig by injection quantity measurements.

From the DE 103 05 525 A1 a method and a device for adapting the pressure wave correction in a high-pressure injection system of a motor vehicle while driving known. In a stationary operating state, the time interval of the two partial injections is gradually reduced. In the case of a change in an operating parameter due to a pressure wave, the value of the change and the time interval are stored and used as the basis for a correction of the pressure wave influence.

From the DE 103 15 817 A1 For example, a method and an apparatus for operating an injection system having a quantity compensation control are known. In this case, the activation duration of an injector is varied and in each case the correction quantity provided by a quantity compensation regulation is detected. In the subsequent operation, the drive duration for which the correction amount is maximum is taken into account in the control for the pilot injection.

This approach provides only limited appropriate values, since the operating conditions are different on a test bench and in the motor vehicle. Influences such as injection back pressure, thermal load due to combustion affect the injection quantity. Quantity corrections that are measured at the hydraulic test bench can therefore only be transferred to a limited extent on engine operation.

Characterized in that in certain operating conditions of the internal combustion engine, the correction values are determined by the distance between a first and a second injection is changed and the dependence of the manipulated variable of a controller, which adjusts the speed to a desired value, from the distance of the first and the second injection is determined, the correction values can be determined much easier.

The procedure according to the invention enables direct vehicle control. This significantly increases the accuracy of the correction. The expense of determining the correction values, in particular their duration, is considerably reduced. It is particularly advantageous if the output signal of a speed controller, in particular of the idle controller, is used. Based on the change in the manipulated variable of this controller with a change in the distance, the correction values for the amount of fuel can be determined in a simple manner.

It is particularly advantageous that this method can be performed both on the test bed and in normal driving. Thus, the method is preferably carried out at the first startup of the vehicle or the internal combustion engine. Furthermore, the method after a repair of the internal combustion engine or the control can be easily performed. In principle, it is even possible to carry out the method during operation under suitable operating conditions.

drawing

The invention is illustrated below with reference to a drawing and embodiments explained. Show it:

1 a block diagram of the procedure according to the invention,

2 various signals plotted over time and

3 a flow chart of the procedure according to the invention.

In 1 the essential elements of the device according to the invention are shown as a block diagram. With 150 is a control unit for controlling a controller 130 , which affects the fuel metering, called. The control unit 150 Among other things, the output signal N of a speed sensor 175 and the output signal FP an accelerator pedal position transmitter 170 fed. The speed signal N reaches the one to an idle controller 153 , The output signal FP of the accelerator pedal encoder 170 arrives at a driver request specification 151 , The speed controller 153 acts on a node 154 with a signal QKL. The driver's default 151 acts on the point of connection 154 with a signal QKW. Furthermore, a pressure wave correction 152 provided that the connection point 154 subjected to a signal QKK. The link point 154 forms from these three input variables and optionally other variables a signal QK for acting on the actuator 130 ,

By means of the writer 130 the amount of fuel to be injected can be adjusted. At the steller 130 is, for example, a solenoid valve or a piezoelectric actuator, which influences the fuel quantity to be injected of an injector, in particular an injector of a common rail system. The idle controller 153 regulates the speed of the internal combustion engine to a desired idle speed. In this case, the idle controller increases or decreases depending on the deviation of the actual speed of the desired speed, the fuel quantity to be injected. Based on the driver's request determines the desired specification 151 a quantity of fuel QKW to be injected, required for the driver's desired driving performance. When the accelerator pedal is actuated, the signal QKW generally determines the quantity of fuel QK to be injected. When the accelerator pedal is not actuated, the output signal QKL of the idle controller is generally determined 153 the amount of fuel QK to be injected.

In today's systems, it is usually provided that a so-called pre-injection takes place before the actual fuel injection. This first injection causes a pressure wave in the supply line to the injector. In principle, this pressure wave can occur in all injection systems. In common-rail systems, the influence on the subsequent second injection is usually so great that it is corrected. This correction is made by the pressure wave correction 152 , In this case, a correction value QKK is determined as a function of the distance between the first and the second partial injection and further operating parameters, such as, for example, the rotational speed or the injected fuel quantity, with which the fuel quantity QK to be injected at the point of connection 154 is corrected.

In a simple embodiment, provision is made for the correction value to be stored in a characteristic field as a function of the distance of the two partial injections.

Such a pressure wave correction is detailed in the DE 197 12 143 A1 shown.

The aim of the procedure described below is to determine these correction values. With the procedure according to the invention, the dependence of the correction values QKK on different operating parameters is determined. In the simplest embodiment, the correction value is determined as a function of the distance D of the two partial injections. In an improved embodiment, additional operating parameters, such as the rotational speed and / or an amount of fuel QK to be injected, are used.

According to the invention, the procedure is as follows. At constant pedal position or constant load, especially when zeroing the accelerator pedal, the speed is through the idle controller 153 regulated to a constant value. In a variation of the distance between the first partial injection and the second partial injection, the injection quantity of the second partial injection varies due to the pressure wave triggered in the first partial injection. The idle controller responds to the changes in quantity and increases or decreases respectively the amount of fuel QKL to be injected in order to keep the speed constant. This means that the course of the amount of fuel to be injected is corrected by the idle controller so that the speed is constant. Deviations based on the pressure wave are compensated by the idle controller. For example, this means that too little fuel is injected due to the pressure wave, so the output QKL of the idle controller increases. If too much fuel is injected, the signal will drop.

According to the invention, the distance between the first and the second partial injection is varied. As a result, the output signal QKL of the idle controller changes according to the pressure wave.

According to the invention, this process is repeated for several operating points. That is, depending on which operating points the pressure wave correction takes place, this measuring method is performed for these operating conditions.

In 2 is over the time T, the distance D of the two partial injections and the output signal QKL of the idle controller 153 applied. In the illustrated embodiment, the distance D between the first and the second injection is plotted with a dashed line. In this case, the distance is increased according to a ramp from the value zero to a value at which no more pressure wave occurs. In one embodiment, it can also be provided that a ramp is used in which the distance from a value at which no pressure wave occurs more, is reduced to the value zero. With a solid line, the output signal of the idle controller QKL is plotted. With increasing distance, this signal fluctuates almost periodically, with the amplitude decaying over time.

As an alternative to the task over time, an application via crankshaft angle can also take place.

The procedure according to the invention is described below with reference to the flow chart of FIG 3 shown. The procedure according to the invention is preferably carried out when the vehicle is on a chassis dynamometer. In principle, this procedure is also possible during normal driving and / or during a test drive. In a first step 300 the load is set to a constant value or checks whether the load assumes a constant value. This is the case, for example, in overrun mode. Then in step 310 a constant speed is specified for the idle controller. In step 320 the value of the distance D between the first and second injection is set to the value zero. In step 330 the value D of the distance between the two partial injections and the output signal QKL of the idle controller is detected. Then in step 340 the value D of the distance is increased by an E value. This value E depends on how exactly the dependence of the correction values on the distance is to be included. Then in step 350 It is checked whether the distance D is greater than a threshold SW. If this is not the case, the program continues with step 330 , ie the next combination of values for the distance and the corresponding output value of the idle controller becomes in step 330 detected. The threshold value SW is preferably selected so that at the corresponding distance, the second partial injection is no longer influenced by the first partial injection. If the value of the distance D is greater than the threshold value SW, then step follows 360 , In step 360 the correction values are determined on the basis of the output signals of the controller QKL. In a simple embodiment, the correction values are proportional to the determined values QKL for the output signal of the idle controller. Ie. in the simplest case, the values are multiplied by a fixed value.

It is particularly advantageous if the program run is carried out again for a further operating state, d. H. For example, it can be provided that different maps are recorded for different pressure values of the rail pressure. Furthermore, it can be provided that corresponding characteristic curves are recorded for different injection quantities and / or rotational speeds. For this purpose, it is necessary that not an idle controller, but a conventional speed controller is used. It regulates the speed to a constant value.

The procedure according to the invention can in principle be carried out in all operating states in which the load which is taken off the internal combustion engine is constant. Ie. the method can be carried out during operation, if such operating conditions exist. Furthermore, the procedure is carried out during initial commissioning or workshop visit. There, the conditions can be specified so that the load is constant.

The method can be performed entirely by the control unit that usually controls the internal combustion engine in the vehicle. Furthermore, it is possible to run individual functions in an external device, in particular in a test device or diagnostic device. This applies in particular to the determination of the correction values based on the output signal QKL of the controller. Furthermore, this external device will initialize the test by specifying certain operating states.

Claims (7)

Method for controlling an internal combustion engine, correction values (QKK) for correcting a quantity (QK) characterizing the quantity of fuel to be injected being determined in certain operating states, wherein the distance (D) between a first partial injection and a second partial injection is changed and the dependence of a manipulated variable (Q) QKL) of a controller ( 153 ), which adjusts the rotational speed to a desired value, is determined from the distance (D) of the first and the second partial injection. A method according to claim 1, characterized in that it is the size of the driving time of an actuating element for the amount of fuel to be injected. A method according to claim 1, characterized in that it is the size of a fuel quantity signal. A method according to claim 1, characterized in that starting from the distance zero, the distance is increased. A method according to claim 1, characterized in that starting from a distance at which the first injection has no influence on the second injection, the distance is reduced. A method according to claim 1, characterized in that starting from the manipulated variable, the correction values are determined. Device for controlling an internal combustion engine, having means which determine correction values (QKK) for correcting a quantity of fuel (QK) characterizing the quantity of fuel to be injected in certain operating states, the means changing the distance (D) between a first partial injection and a second partial injection and the dependence a manipulated variable (QKL) of a regulator ( 153 ), which adjusts the speed to a desired value, determine the distance (D) of the first and the second partial injection.

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