DE102005011836A1 - Method for controlling internal combustion engine involves determination of correction value in specific operating condition for correction of injected fuel characteristic value - Google Patents

Abstract

The method involves determination of correction value (QKK) in specific operating condition for correction of the injected fuel characteristic value (Qk). The distance between the first partial injection and a second partial injection is changed. Depending on the regulation variable (QKL) of regulator (153), the distance between the first partial injection and second partial injection is determined. An independent claim is also included for the device for controlling internal combustion engine.

Description

The 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 described.

The Pressure wave correction corrects the influence of the pressure wave the injection quantity. This is done essentially by the fact that for the respective Operating point determined a correction amount and with the desired spray quantity is charged. The operating point is essentially through determines the distance between the two partial injections. In conventional Systems undergo experimental correction on a hydraulic test bench Injection quantity measurements determined.

These Procedure provides only limited suitable values, since the operating conditions on a test bench and are different in the motor vehicle. Influences such as injection back pressure, Thermal stress due to the combustion affect the injection quantity A out. Quantity corrections that are measured at the hydraulic test bench can therefore only conditionally transmitted to the engine operation become.

Thereby, that in certain operating conditions the internal combustion engine, the correction values are determined thereby that the distance between a first and a second injection is changed and the dependence the manipulated variable of a Regulated from the distance of the first and second injection will, can the correction values are determined much easier.

The inventive approach allows a direct condition on the vehicle. This will increase the accuracy the correction increased significantly. The effort of determining the correction values, in particular their Duration, is significantly reduced. It is particularly advantageous if the output signal of a speed controller, in particular the Idle controller, is used. Starting from the change the manipulated variable of this Regulator at a change of the distance In a simple way, the correction values for the amount of fuel can be determined.

Especially It is advantageous that this method both on the test bench as can also be carried out in normal driving. This is how the procedure works Preferably at the first start of the vehicle or the Internal combustion engine performed. Furthermore, the method may be after a repair of the internal combustion engine or the control can be easily performed. In principle it even possible to carry out the procedure during operation under suitable operating conditions.

drawing

The Invention is shown below with reference to a drawing and Embodiments explained. It demonstrate:

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 of an accelerator pedal position sensor 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 it, 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, depending on the distance between the first and the second partial injection and other operating parameters, such as. The speed or the injected fuel quantity a correction turwert QKK determined with the injected fuel quantity QK in the node 154 is corrected.

at a simple embodiment is provided for this purpose that in one Map dependent stored from the distance of the two partial injections of the correction value is.

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

aim The procedure described below is these correction values to determine. With the procedure according to the invention is the dependence the correction values QKK determined by various operating characteristics. In the simplest embodiment the correction value becomes dependent determined by Astand D of the two partial injections. In an improved Embodiment will be additional Operating parameters, such as the speed and / or a fuel quantity QK to be injected 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 to a constant value. regulated. 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 will now the distance between the first and the second partial injection varied. This has the consequence that the output signal QKL of the idle controller changes according to the pressure wave.

According to the invention, it is provided that this process for several operating points is repeated. That is, depending on which operating points the pressure wave correction is done this measuring method for this Operating conditions performed.

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.

alternative to the over the time can also be applied by crankshaft angle.

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 becomes set the load to a constant value or check that 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. This means that in the simplest case the values are multiplied by a fixed value.

Especially It is advantageous if the program run for another operating state again carried out is, i. For example, it can be provided that for different pressure values of the Rail map different maps are included. Furthermore can be provided that for different injection quantities and / or speeds corresponding Characteristic curves are recorded. For this it is necessary that not an idle controller, but a common one Speed controller is used. It regulates the speed to a constant value.

The inventive approach can be carried out in principle in all operating states, in which the load that is taken off the internal combustion engine, is constant. That The procedure can be on the fly if such operating conditions present, carried out become. Furthermore, the procedure becomes during initial startup or workshop visit. There, the conditions can be specified be that the load is constant.

The Procedure can be complete from the controller, that usually the internal combustion engine controls are performed in the vehicle. Further Is it possible individual functions in an external device, in particular in a test device or diagnostic device run allow. This is especially true for the determination of the correction values from the output QKL of the regulator. Furthermore, this external Device the Examination by Specification of certain operating states initialize.

Claims (8)

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 ) is determined from the distance (D) of the first and the second partial injection. Method according to claim 1, characterized in that that it is the size of the Activation time of an actuating element for the amount of fuel to be injected is. Method according to claim 1, characterized in that that the size is one Fuel quantity signal is. Method according to claim 1, characterized in that that starting from the distance zero, the distance is increased. Method according to claim 1, characterized in that that starting from a distance at which the first injection has no influence on the second injection, the distance decreases becomes. Method according to claim 1, characterized in that that starting from the manipulated variable, the correction values be determined. Method according to claim 1, characterized in that the controller controls the speed to a setpoint. Device for controlling an internal combustion engine, having means which, in certain operating states, determine correction values (QKK) for correcting a variable (QK) characterizing the quantity of fuel to be injected, 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 determine the distance (D) of the first and the second partial injection.