Method for regulating a fuel delivery system

Abstract

A method for regulating a fuel delivery system of an internal combustion engine in a motor vehicle having a fuel delivery pump for supplying the internal combustion engine with fuel, the fuel delivery pump having a pump mechanism driveable by an electric motor actuable by a control signal, and a pressure-sensor-free pressure monitor being provided in the fuel delivery system, includes: predefining a target rotational speed for the electric motor based on the control signal; predefining an upper rotational speed limit and/or a lower rotational speed limit for the target rotational speed, wherein the upper rotational speed limit depends on the maximum fuel requirement of the internal combustion engine, and the lower rotational speed limit depends on the minimum fuel requirement of the internal combustion engine; and determining the target rotational speed by a pressure-sensor-free calculation method.

Claims

1. A method for regulating a fuel delivery system of an internal combustion engine in a motor vehicle having a fuel delivery pump for supplying the internal combustion engine with fuel, the fuel delivery pump having a pump mechanism driveable by an electric motor actuable by a control signal, and a pressure-sensor-free pressure monitor being provided in the fuel delivery system, the method comprising: predefining a target rotational speed for the electric motor based on the control signal; predefining an upper rotational speed limit and/or a lower rotational speed limit for the target rotational speed, wherein the upper rotational speed limit depends on the maximum fuel requirement of the internal combustion engine, and the lower rotational speed limit depends on the minimum fuel requirement of the internal combustion engine; determining the target rotational speed by a pressure-sensor-free calculation method; and calibrating the fuel delivery system by: determining an actual fuel volume based on an actual rotational speed and an actual pressure based on a first characteristic diagram, and entering the determined actual fuel volume into an inverse characteristic diagram, produced by switching the axes of the first characteristic diagram.

2. The method as claimed in claim 1, further comprising changing the rotational speed of the electric motor if the determined target rotational speed lies between the determined upper rotational speed limit and the determined lower rotational speed limit.

3. The method as claimed in claim 1, wherein the target rotational speed is formed by a defined rotational speed value reached during an overrun operation of the motor vehicle, wherein, during the overrun operation, a fuel volume that depends on the actual load of the internal combustion engine is consumed.

4. The method as claimed in claim 1, wherein the rotational speed limits are determined based upon: actual fuel requirements of the internal combustion engine and/or target fuel requirements of the internal combustion engine; and actual pressures in the fuel delivery system and/or target pressures in the fuel delivery system.

5. The method as claimed in claim 1, wherein a value for a pressure in the fuel delivery system is used for determining the rotational speed limits, a value for pressure in the fuel delivery system being a preset value determined from characteristic values of the internal combustion engine and/or of the motor vehicle.

6. The method as claimed in claim 1, further comprising determining, during overrun operation of the motor vehicle, a maximum actual fuel requirement of the internal combustion engine and/or a minimum actual fuel requirement of the internal combustion engine and/or the actual fuel requirement of the internal combustion engine based on characteristic values that describe an operating state of the internal combustion engine.

7. The method as claimed in claim 1, further comprising correcting a fuel requirement of the internal combustion engine based on an offset volume, wherein the offset volume represents an additional fuel requirement of fuel-receiving elements in the fuel delivery system.

8. The method as claimed in claim 1, the calibrating of the fuel delivery system further comprising: determining a comparison rotational speed and/or a comparison pressure based on the inverse characteristic diagram; and determining a deviation between the actual rotational speed and the comparison rotational speed or between the actual pressure and the comparison pressure.

9. The method as claimed in claim 1, further comprising: matching the target rotational speed calculated in the pressure-sensor-free calculation method with the determined rotational speed limits; and adapting the determined target rotational speed to a value inside the rotational speed limits if the determined target rotational speed lies outside the rotational speed limits.

10. A method for regulating a fuel delivery system of an internal combustion engine in a motor vehicle having a fuel delivery pump for supplying the internal combustion engine with fuel, the fuel delivery pump having a pump mechanism driveable by an electric motor actuable by a control signal, and a pressure-sensor-free pressure monitor being provided in the fuel delivery system, the method comprising: predefining a target rotational speed for the electric motor based on the control signal; predefining an upper rotational speed limit and/or a lower rotational speed limit for the target rotational speed, wherein the upper rotational speed limit depends on the maximum fuel requirement of the internal combustion engine, and the lower rotational speed limit depends on the minimum fuel requirement of the internal combustion engine; and determining the target rotational speed by a pressure-sensor-free calculation method, wherein a target fuel volume to be delivered by the fuel delivery pump and a target pressure are used for the determination of the target rotational speed, wherein the target rotational speed is determined based on a characteristic diagram that maps a physical relationship between the rotational speed, the delivered fuel volume and a pressure prevailing in the fuel delivery system.

11. A method for regulating a fuel delivery system of an internal combustion engine in a motor vehicle having a fuel delivery pump for supplying the internal combustion engine with fuel, the fuel delivery pump having a pump mechanism driveable by an electric motor actuable by a control signal, and a pressure-sensor-free pressure monitor being provided in the fuel delivery system, the method comprising: predefining a target rotational speed for the electric motor based on the control signal; predefining an upper rotational speed limit and/or a lower rotational speed limit for the target rotational speed, wherein the upper rotational speed limit depends on the maximum fuel requirement of the internal combustion engine, and the lower rotational speed limit depends on the minimum fuel requirement of the internal combustion engine; determining the target rotational speed by a pressure-sensor-free calculation method; and determining the upper rotational speed limit based on: a maximum fuel requirement of the internal combustion engine; a value for pressure in the fuel delivery system; and a characteristic diagram specific to a respective fuel delivery system and that describes a relationship between a delivered fuel volume, the pressure in the fuel delivery system and a rotational speed of the fuel delivery pump.

12. A method for regulating a fuel delivery system of an internal combustion engine in a motor vehicle having a fuel delivery pump for supplying the internal combustion engine with fuel, the fuel delivery pump having a pump mechanism driveable by an electric motor actuable by a control signal, and a pressure-sensor-free pressure monitor being provided in the fuel delivery system, the method comprising: predefining a target rotational speed for the electric motor based on the control signal; predefining an upper rotational speed limit and/or a lower rotational speed limit for the target rotational speed, wherein the upper rotational speed limit depends on the maximum fuel requirement of the internal combustion engine, and the lower rotational speed limit depends on the minimum fuel requirement of the internal combustion engine; determining the target rotational speed by a pressure-sensor-free calculation method; and determining the lower rotational speed limit based on: a minimum fuel requirement of the internal combustion engine; a value for pressure in the fuel delivery system; and a characteristic diagram specific to a respective fuel delivery system and that describes a relationship between a delivered fuel volume, the pressure in the fuel delivery system and a rotational speed of the fuel delivery pump.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following text, the invention will be explained in detail on the basis of exemplary embodiments with reference to the drawings, in which:

(2) FIG. 1 shows a characteristic diagram illustrates the delivered volume against the rotational speed, wherein curves of equal pressure are illustrated in the characteristic diagram;

(3) FIG. 2 shows a block diagram of a stoichiometry module for determining the fuel requirement of an internal combustion engine;

(4) FIG. 3 shows an exemplary use of a stoichiometry module as it is already shown in FIG. 2; and

(5) FIG. 4 shows a block diagram that illustrates one possible embodiment of the method according to the invention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

(6) FIG. 1 is a characteristic diagram 1 illustrating 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 denoted with the reference numeral 2. The delivery volume of the fuel delivery pump is plotted on the Y-axis, which is denoted with the reference numeral 3. In the quadrant 4 spanned by the axes 2, 3, a plurality of curves 5 is illustrated. The curves 5 are isobars and thus describe ranges of constant pressure. The characteristic diagram 1 is specific to a specific fuel delivery system. The characteristic diagram changes depending on, inter alia, the fuel delivery pump used, the lines used and many other factors. Qualitatively, however, the characteristic diagrams for the three described variables always look like the characteristic diagram 1 illustrated in FIG. 1.

(7) On the basis of the characteristic diagram 1, if two variables are known, it is possible to determine the respective third variable. Starting from a known rotational speed, which may be given, for example, by the rotational speed 6, at a known pressure 7, the associated delivery volume 8 can be determined. Furthermore, for a constant delivery volume 8 at a changed pressure 9, it is then also possible for a changed, associated rotational speed 10 to be determined. This is appropriate, for example, if a known delivery volume 8 is to be delivered at an increased pressure 9 since the required rotational speed 10 can be determined easily in this way.

(8) The pressure 7, 9 in the fuel delivery system increases along the arrow 11. For the purpose of checking and/or calibrating values, it is also possible for a so-called inverse characteristic diagram to be used, wherein in the case of the inverse characteristic diagram, the X-axis 2 and the Y-axis 3 are transposed. For the purpose of calibration, starting from two known values, it is possible for the respectively missing third value to be determined. With knowledge of the third determined value, it is then possible, with the aid of a known second value, for the still unknown value of the three values to be deduced in the inverse characteristic diagram or in reverse in the characteristic diagram 1. The latter value can then be matched with the actually measured value, and, on the basis of the difference that sometimes occurs, calibration can be carried out.

(9) FIG. 2 shows a block diagram 20. The block 21 represents an interface to the remaining motor vehicle. Various pieces of information in the form of characteristic values can be taken from the block 21. In the example of FIG. 2, output from the distributor block 22 are the characteristic values target pressure via the signal line 23, the accelerator pedal position via the signal line 24, and the boost pressure of the turbocharger via the signal line 25. In alternative configurations, other values may also be used, additionally or alternatively. These include in particular different temperatures, the fuel/air ratio, the motor rotational speed or the measurement values of the lambda probe.

(10) The block 26 forms a so-called stoichiometry module. The fuel requirement is calculated in the block 26 on the basis of the characteristic values from the block 21 or 22. For example, the minimum fuel requirement, the maximum fuel requirement and a fuel requirement for the overrun operation may be determined. Output from the stoichiometry module 26 via the signal line 27 is the currently maximum possible fuel requirement, via the signal line 28 is the currently minimum possible fuel requirement and via the signal line 29 is the fuel requirement during the overrun operation of the motor vehicle. The different fuel requirements may subsequently be processed to form further characteristic values.

(11) The stoichiometry module 26 serves in particular for determining the possible fuel requirement of the internal combustion engine with the aid of characteristic values which originate directly from the operation of the internal combustion engine.

(12) The block diagram shown in FIG. 2 is illustrated again in Figure as part of the block diagram illustrated there. Here, the reference signs are retained for identical elements.

(13) FIG. 3 shows a stoichiometry module 26, as it has been shown already in FIG. 2. FIG. 3 reflects a specific application for a particular operational situation of the internal combustion engine. The rotational speed 30 of the internal combustion engine, the accelerator pedal position 31 of the motor vehicle and the boost pressure 32 of the turbocharger installed at the internal combustion engine are passed into the stoichiometry module 26. A value for the fuel requirement of the internal combustion engine is passed on to an output display 34 via the signal line 33. The value indicated on the display 34 is the maximum fuel requirement of the internal combustion engine in the situation considered. A second value is output to the second display 36 via the signal line 35. The value corresponds to the minimum fuel requirement of the internal combustion engine in the situation considered.

(14) The values output on the displays 34 and 36 always relate to the input variables coming from the blocks 30, 31 and 32. The maximum and the minimum fuel requirement thus constantly relate to the operating state of the internal combustion engine that prevailed at the moment of acquisition of the input variables coming from the blocks 30, 31 and 32.

(15) FIG. 4 shows a block diagram 40. The stoichiometry module from FIG. 2 is shown by the reference sign 26. Identical elements are provided with the same reference signs. In addition to the input variables, which originate from the motor vehicle via block 21, the rotational speed of the fuel delivery pump, in particular the target rotational speed, is provided as an input variable via the block 41. The target rotational speed 41 may be determined via a pressure-sensor-free method and serves for the adaptation of the fuel volume delivered by the fuel delivery pump.

(16) Furthermore, an offset volume is introduced via block 42. The offset volume represents an additional volume that has to be delivered in addition to the fuel volume required by the internal combustion engine by the fuel delivery pump in order to ensure fault-free operation of the fuel delivery system. The offset volume may be required, for example, for the operation of an ejector pump.

(17) The currently maximum fuel requirement of the internal combustion engine is output from the stoichiometry module 26 via the signal line 43. This is added to the offset volume in the summation block 44 and entered into the block 45. Additionally, a presetting for a target pressure to be reached in the fuel delivery system is also passed into the block 45, which target pressure is branched off from the signal line 23.

(18) The target pressure coming from the signal line 23 is likewise entered into the block 46. Additionally, the currently minimum fuel requirement is passed into the block 46 via the signal line 47. The minimum fuel requirement is not offset with the offset volume since the actually minimum fuel requirement of the internal combustion engine goes into the block 46 for further processing. In an alternative configuration, it is also possible, however, for the minimum fuel requirement to be offset with the offset volume.

(19) The target pressure from the signal line 23 likewise goes into the block 47. Moreover, during overrun operation, the fuel requirement, which is output from the stoichiometry module 26 along the signal line 49, goes into the block 47. Before the block 47, the fuel requirement in overrun operation is, in the summation block 48, likewise offset with the offset volume from block 42.

(20) In the blocks 45, 46 and 47, a rotational speed presetting is then determined from the target pressure and the respectively determined fuel volume, the latter of which is composed of the respective fuel requirement and if appropriate the offset volume, in each case with the aid of characteristic diagrams, as they are illustrated for example in FIG. 1. The upper rotational speed limit is determined from the block 45, and the lower rotational speed limit is determined from block 46. These two rotational limits span a target range for a target rotational speed for the fuel delivery pump. A rotational speed presetting, which is used as a target rotational speed in particular if the motor vehicle is in overrun operation, is determined in block 47.

(21) Not only the rotational speed limits determined in the blocks 45 and 46 but also the target rotational speed from the block 41 go into the block 49. A check as to whether or not the target rotational speed lies inside the rotational speed limits takes place in block 49. If the target rotational speed lies inside the limits, the fuel delivery pump is subsequently regulated to the determined target rotational speed.

(22) In addition to the target rotational speed from block 41 and the rotational speed presetting for the overrun operation from block 47, the upper rotational speed limit from block 45 also goes into the block 50. In this way, it is possible to check whether the target rotational speed, predefined during overrun operation, for the fuel delivery pump is below the upper rotational speed limit, and by how much the target rotational speed from block 41 if appropriate differs from the rotational speed determined in the block 47. Adaptation of the rotational speed determined in block can take place in block 50. Alternatively, the target rotational speed determined from block 41 can be adapted, or some other processing can be performed.

(23) Finally, a target rotational speed is output from both the block 49 and from the block 50, which speed, in the case of the block 49, in any case lies inside the rotational speed limits. A target rotational speed lying outside the rotational speed limits either is not passed, or is on correspondingly corrected to a value inside the rotational speed limits, by the block 49.

(24) A check as to whether the motor vehicle or the internal combustion engine actually being operated in overrun operation takes place in the block 51. If this is the case, the target rotational speed coming from the block 50 is output from the block 51. If overrun operation is not present, the target rotational speed determined in the block 49 is output from block 51.

(25) In the block 52 connected downstream, there may occur a weighting of the target rotational speed or a signal conversion into a format that is suitable for the actuation of the fuel delivery pump or of the associated electric motor. The determined target rotational speed is then passed as a control signal to the fuel delivery pump or to the electric motor of the fuel delivery pump via the block 53.

(26) FIG. 4 shows an exemplary embodiment of a block diagram for realizing a method according to the invention. The illustration of FIG. 4 is in particular not of a restrictive nature and does not exclude possible solutions that are not explicitly shown.

(27) The exemplary embodiments of FIGS. 1 to 3 are also in particular not of a restrictive nature, and serve for illustrating the concept of the invention.

(28) Thus, while there have been 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.