Feedback control method for a fuel delivery system

Abstract

A feedback control method for a fuel delivery system of an internal combustion engine, having a fuel delivery pump for supplying fuel, the fuel delivery pump having a pump mechanism driven by an electric motor, which is controlled by a generated control signal. The current fuel volume delivered by the fuel delivery pump and the prevailing fuel requirement of the internal combustion engine are included in the control signal. The prevailing fuel requirement is determined using characteristic variables that characterize the operating state of the internal combustion engine.

Claims

1. A feedback control method for a fuel delivery system of an internal combustion engine in a motor vehicle, having a fuel delivery pump that supplies the internal combustion engine with fuel, the fuel delivery pump has a pump mechanism driven by an electric motor, the electric motor controlled by a control signal, comprising: generating the control signal for the electric motor, wherein a current fuel volume delivered by the fuel delivery pump and a prevailing fuel requirement of the internal combustion engine are included in determining the control signal; determining the prevailing fuel requirement based at least in part on characteristic variables that characterize an operating state of at least one of the internal combustion engine and the motor vehicle; and calibrating the fuel delivery system, by: determining the actual fuel volume by a characteristic map using a current rotational speed and a current pressure applied to an inverse characteristic map; determining at least one of a comparative rotational speed and a comparative pressure from the inverse characteristic map; and determining a deviation between at least one of: the current rotational speed and the comparative rotational speed and the current pressure and the comparative pressure.

2. The method as claimed in claim 1, further comprising: determining the current fuel volume delivered by the fuel delivery pump from a current pressure prevailing in the fuel delivery system and a current rotational speed of the pump mechanism of the fuel delivery pump based at least in part on at least one characteristic map.

3. The method as claimed in claim 2, further comprising: determining the prevailing fuel requirement of the internal combustion engine based at least in part on at least one of: a gas pedal position, a charging pressure of a turbocharger, a rotational speed of the internal combustion engine, a delivered air mass, a fuel/air ratio in the internal combustion engine, a lambda value, and an air temperature.

4. The method as claimed in claim 1, wherein the current fuel volume delivered by the fuel delivery pump is determined at a time at which a delivered current fuel volume is still unchanged in comparison with an already changed fuel requirement of the internal combustion engine.

5. The method as claimed in claim 4, further comprising: determining a fuel volume setpoint to be delivered from a difference between the current fuel volume delivered by the fuel delivery pump and the fuel requirement of the internal combustion engine; and determining a rotational speed setpoint for the fuel delivery pump from the a fuel volume setpoint.

6. The method as claimed in claim 5, wherein the fuel volume setpoint is processed with a pressure setpoint in the fuel delivery system to form the rotational speed setpoint.

7. The method as claimed in claim 6, wherein the pressure setpoint in the fuel delivery system is determined by a differential value, input into a PID controller, between a default value for the pressure and a current pressure.

8. The method as claimed in claim 5, further comprising: correcting the fuel volume setpoint by an offset value, wherein the offset value is caused by additional elements in the fuel delivery system.

9. The method as claimed in claim 4, wherein the fuel requirement of the internal combustion engine changes before the current fuel volume delivered by the fuel delivery pump is changed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following, the invention will be explained in detail by using exemplary embodiments and with reference to the drawings, in which:

(2) FIG. 1 is a characteristic map that represents the delivered volume over the rotational speed, curves of identical pressure being illustrated in the characteristic map;

(3) FIG. 2 is a block diagram that represents the determination of the fuel requirement of an internal combustion engine from engine-specific characteristic variables;

(4) FIG. 3 is a block diagram that shows an exemplary representation of the method; and

(5) FIG. 4 is a block diagram of a fuel delivery system of an internal combustion engine.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

(6) FIG. 1 is a characteristic map 1, which represents the relationships between the volume delivered by the fuel delivery pump, the rotational speed of the fuel delivery pump and the pressure in the fuel delivery system. The rotational speed is plotted on the X axis, which is identified by the designation 2. The delivery volume of the fuel delivery pump is plotted on the Y axis, which is identified by the designation 3. In the quadrant 4 spanned by the axes 2, 3, a plurality of curves 5 are illustrated. The curves 5 are isobars and thus describe regions of constant pressure. The characteristic map 1 is specific to a specific fuel delivery system. The characteristic map changes, amongst other things, depending on the fuel delivery pump used, the lines used, and many other factors. In qualitative terms, however, the characteristic maps for the three variables described always look like the characteristic map 1 illustrated in FIG. 1.

(7) On the basis of the characteristic map 1, given knowledge of two variables, the respective third variable can be determined. Starting from a known rotational speed which, for example, can be given by the rotational speed 6, the associated delivery volume at a known pressure 7 can be determined. Going further, a changed associated rotational speed 10 for a constant delivery volume 8 at a changed pressure 9 can also be determined. This is expedient, for example, if a known delivery volume 8 is to be delivered at an increased pressure 9, since in this way the necessary rotational speed 10 can easily be determined.

(8) Along the arrow 11, the pressure 7, 9 in the fuel delivery system increases. For the purpose of checking and/or calibrating values, a so-called inverse characteristic map can also be used, wherein in this inverse characteristic map the X axis 2 and the Y axis 3 are interchanged with each other. For the purpose of calibration, starting from two known values, the respective missing third value can be determined. Given knowledge of the third determined value, it is then possible in the inverse characteristic map, or in reverse fashion in the characteristic map 1, for conclusions about the as yet unknown value of the three values to be drawn with the aid of a known second value. Said unknown value can then be compared with the actual measured value and, by using the difference which occurs under certain circumstances, a calibration can be carried out.

(9) FIG. 2 shows a block diagram 20. Block 21 represents an interface to the rest of the vehicle. Different information in the form of characteristic variables can be taken from block 21. In the example of FIG. 2, from the distributor block 22, the characteristic value engine rotational speed is output via the signal line 23, the gas pedal position is output via the signal line 24, and the charging pressure of the turbocharger is output via the signal line 25. In alternative configurations, other values can also be used. These include in particular different temperatures, the fuel/air ratio or the measured value from the lambda probe.

(10) Block 26 forms a so-called stoichiometry module. In block 26, on the basis of the characteristic values from block 21 and/or 22, the fuel requirement is calculated. It is possible, for example, for the minimum fuel requirement, the maximum fuel requirement, and an idling fuel requirement to be determined. All three fuel consumption rates or else only an individual fuel consumption rate can finally be passed on via the signal line 27 to following applications.

(11) The stoichiometry module is used in particular to determine the instantaneous current fuel requirement of the internal combustion engine with the aid of characteristic values which originate directly from the operation of the internal combustion engine. By a subsequent comparison of the instantaneous fuel requirement of the internal combustion engine and the actually delivered quantity of fuel, it is possible to determine the difference, which can be used as target value for changed control of the electric motor.

(12) FIG. 3 shows a block diagram 30, wherein the block diagram 30 depicts an exemplary embodiment of the method according to the invention. The lower left-hand region is formed by the stoichiometry module 26 already shown in FIG. 2. The same designations are therefore used for corresponding constituents.

(13) From block 31, the rotational speed of the fuel delivery pump is entered into the box 32, which is used to determine the fuel volume delivered by the fuel delivery pump. Also input into block 32 is a value for the pressure prevailing in the fuel delivery system, which is introduced into the block diagram via block 33. This pressure value from block 33 can be measured, for example, by a pressure sensor.

(14) In block 32, with the aid of a characteristic map as shown, for example, in FIG. 1, the fuel volume delivered is determined as a function of the measured pressure and the associated rotational speed. The fuel volume delivered is led via signal line 34 into block 35, where the instantaneously delivered fuel volume is compared with the fuel requirement determined in block 26. The differential value generated here represents a measure of the more or less fuel needed. The differential value generated is passed on into block 37 via the signal line 36.

(15) Also entered into block 37 is a value for the pressure setpoint in the fuel delivery system, weighted by a controller 38, in particular a PID controller. Said pressure setpoint is determined from a default value 39 entered into the block diagram, in that, in a differential block 40, the default value 39 is set against the value originating from block 33 of the pressure prevailing in the fuel delivery system. The difference from the differential block 40 is entered into the controller 38, wherein the value is weighted in accordance with a defined algorithm or default values predefined externally. In an alternative configuration, the default value 39 can also be predefined externally without undergoing any further correction.

(16) In block 37, finally, by using the weighted pressure value from the controller 38 and the differential value of the fuel volume determined in block 35, a default rotational speed is determined for the fuel delivery pump. The default rotational speed is output to block 42 via signal line 41.

(17) In block 37, it is possible to use a characteristic map, as is already used for example in block 32. In addition, predefined algorithms can be used to determine the rotational speed setpoint or a default rotational speed.

(18) In alternative developments, the individual blocks can also be interlinked further with one another, so that, for example, the function of the controller in block 38 depends on the results determined in other blocks. In this way, the control quality can be increased considerably.

(19) The different features of the individual exemplary embodiments can also be combined with one another.

(20) The exemplary embodiments of FIGS. 1 to 3 in particular have no restrictive character and are used to illustrate the idea of the invention. In particular, FIG. 3 shows only one possible configuration of the method according to the invention, without ruling out other alternatives covered by the protective scope of the claims.

(21) FIG. 4 is a block diagram of a fuel delivery system of an internal combustion engine 102. A fuel delivery system of the internal combustion engine has a fuel delivery pump 104 for supplying fuel, the fuel delivery pump 104 has a pump mechanism driven by an electric motor 106, which is controlled by a generated control signal in a controller 108. The current fuel volume delivered by the fuel delivery pump 104 and the prevailing fuel requirement of the internal combustion engine are included in the control signal. The prevailing fuel requirement is determined using characteristic variables that characterize the operating state of the internal combustion engine which can include one or more of a pressure measured by a pressure sensor 110 and a position of a gas pedal 112.

(22) Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.