METHOD FOR DETERMINIG THE LOADING STATUS OF A FILTER

Abstract

A method for determining the load status of a filter mounted in a fuel supply system, comprising a fuel supply pump and a control unit for controlling the fuel supply pump, the time curve of the rotational speed of the fuel supply pump being detected over a predetermined period of time, and at least one value of the time curve of the rotational speed and its associated detection time being compared with a comparative value stored in a control unit

Claims

1. A method for determining the loading state of a filter situated in a fuel supply system, comprising the steps of: providing a fuel supply pump; providing a control unit for controlling the fuel supply pump; providing a temporal progression of the rotational speed of the fuel supply pump, the temporal progression having at least one value; and providing at least one comparative value stored in the control unit; detecting the temporal progression of the rotational speed of the fuel supply pump over a predefined period of time; comparing the at least one value of the temporal progression of the rotational speed and its associated detection time with the at least one comparative value stored in the control unit.

2. The method of claim 1, further comprising the steps of: providing at least one predefined rotational speed of the fuel supply pump; comparing the detection time at which the at least one predefined rotational speed is reached with the at least one comparative value assigned to the predefined rotational speed; deriving the loading state of the filter from the difference between the detection time and the temporal comparative value.

3. The method of claim 1, further comprising the steps of defining the detection time by a pre-definable current intensity.

4. The method of claim 1, further comprising the steps of detecting the temporal progression of the rotational speed over the predefined period of time, such that the predefined period of time corresponds to a run-up of the fuel supply pump from a standstill.

5. The method of claim 1, further comprising the steps of continuously comparing the detected temporal progression and the stored comparative values.

6. The method of claim 1, further comprising the steps of determining the comparative values based on the temperature of the fuel.

7. The method of claim 1, further comprising the steps of determining the comparative values based on the fuel quality of the fuel.

8. The method of claim 1, further comprising the steps of: providing a reference point; calculating the pressure in the fuel delivery system; operating the fuel supply pump with a constant current intensity at the reference point such that the fuel supply pump reaches a constant rotational speed that is dependent on the pressure in the fuel delivery system.

9. The method of claim 8, further comprising the steps of: comparing the constant rotational speed of the fuel supply pump with a comparative rotational speed stored in the control unit; detecting the pressure in the fuel supply system based on the difference between the constant rotational speed of the fuel supply pump and the rotational speed stored in the control unit.

10. The method of one of preceding claims 8, further comprising the steps of: providing a minimum quantity of fuel; and providing a maximum quantity of fuel that is presently demanded; approaching the reference point only when the minimum quantity of fuel required at the reference point is greater than the maximum quantity of fuel that is presently demanded.

11. The method of claim 1, further comprising the steps of: providing a display system; storing at least one limit value in the control unit, outputting a message on the display system if the limit value is exceeded.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Advantageous refinements of the present invention are described in the dependent claims and in the description of the Figures that follows. The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:

[0050] FIG. 1 is a diagram showing the temporal progression of the rotational speed of a fuel supply pump, with the continuous time on the X-axis and a rotational speed of a fuel supply pump on the Y-axis;

[0051] FIG. 2 is a schematic representation of the current uptake of a fuel supply pump with respect to the rotational speed, wherein the curves for different pressures in the fuel supply system are represented;

[0052] FIG. 3 is a schematic representation of the prevailing pressure in the fuel supply system with respect to the rotational speed of the fuel supply pump, wherein the curves for different current intensities are represented; and

[0053] FIG. 4 is a flow chart for illustrating the method according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0054] The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

[0055] FIG. 1 shows a diagram 1 in which the temporal progression of the rotational speed of a fuel supply pump is represented. The time is continuously plotted on the X-axis 2, proceeding from the zero point 3. The rotational speed is plotted on the Y-axis 4, increasing from the zero point 3.

[0056] The curve 5 represents one possible progression of the rotational speed of the fuel supply pump in an operating situation. In the exemplary embodiment in FIG. 1, the zero point 3 forms an operating point at which the fuel supply pump is at a standstill. The temporal progression of the rotational speed represented by the curve 5 corresponds to a run-up of the fuel supply pump from a standstill. This run-up is triggered by an energization of the fuel supply pump. Fuel supply pumps are controlled, inter alia, by varying the current intensity.

[0057] The temporal progression of the rotational speed 5 shown in FIG. 1 is the reaction of a fuel supply pump to a step function, i.e., the abrupt application of a voltage and, therefore, the flowing of a current. The rotational speed of the fuel supply pump increases in accordance with the design-specific boundary conditions and the environmental conditions of the fuel supply pump, such as, for example, the pressure ratios in the fuel to be delivered, at a level predefined by the applied voltage or the flowing current. Given a constant current intensity, a constant rotational speed will set in, provided the boundary conditions and environmental conditions remain unchanged.

[0058] The curve 5 shows a rotational speed progression for an exemplary fuel supply pump in a fuel supply system comprising a new, non-loaded filter. For each fuel supply pump having the boundary conditions and environmental conditions, a characteristic temporal progression of the rotational speed results in response to a defined step function.

[0059] By changing the pump type or, by changing the environmental conditions in the fuel supply system, changes result in the temporal progression 5 of the rotational speed. In FIG. 1, the two exemplary rotational speed curves 6 and 7 show a run-up of the fuel supply pump, wherein the rotational speed curves 6 and 7 are each based on changed environmental conditions.

[0060] In FIG. 1, it is apparent that, in the case of the rotational speed curves 6 and 7, a given rotational speed is reached at a later point in time than is the case with the rotational speed curve 5. This is caused, for example, by a higher prevailing pressure in the fuel supply system. The pressure in the fuel supply system is influenced, inter alia, by the loading state of the filter. An increased loading state results in an increased pressure in the fuel supply system, which, in turn, contributes to a delayed attainment of the desired rotational speed of the fuel supply pump.

[0061] Within the scope of the method according to the invention for determining the loading of the filter, a rotational speed curve 5, which is characteristic of the fuel supply system in the starting state, is compared with the rotational speed curves 6 and 7. The loading state of the filter is inferred from the time difference which is detected for a certain rotational speed level.

[0062] The arrow 8 shows the direction in which the rotational speed curves 6, 7 travel due to the increasing loading of the filter or the increasing pressure in the fuel supply system.

[0063] FIG. 2 shows a schematic representation of the current uptake of a fuel supply pump with respect to the rotational speed. The curves 10, 11, 12, 13 and 14 show the current uptake for a constant pressure in the fuel supply system in each case. The curve 10 shows the lowest pressure and the curve 14 shows the highest pressure. The pressure increases in the direction of the arrow 15.

[0064] The rotational speed of the fuel supply pump is plotted on the X-axis 18 and the current uptake of the fuel supply pump is plotted on the Y-axis 19.

[0065] The curves 16 and 17 represent limit value curves which are, for example, limits for generating a warning message, which is output when pressures associated with the limits are exceeded.

[0066] Given a constant pressure in the fuel supply system, there is a defined current uptake for each rotational speed of the fuel supply pump. Due to the approach to a defined reference point in a targeted manner, as is described in the method according to the invention, a change in the pressure in the fuel supply system is detected and, therefore, the loading of the filter may be inferred.

[0067] FIG. 3 shows a schematic representation of the pressure prevailing in the fuel supply system with respect to the rotational speed of the fuel supply pump. The rotational speed of the fuel supply pump is plotted on the X-axis 20. The pressure in the fuel supply pump is plotted on the Y-axis 21. The curves 22, 23, 24, 25 and 26 each represent lines having a constant current intensity. The current intensity increases in the direction of the arrow 27 in this case. The curves 28 and 29 represent limit values, and if the limit values are exceeded, for example, a warning message is generated.

[0068] FIGS. 2 and 3 also show the close correlation between the rotational speed, the current flowing to the fuel supply pump, and the pressure prevailing in the fuel supply system. Due to the close connection of the three variables to each other, when two of the three variables are known, it is possible to determine the third variable with high accuracy. In addition, due to the great correlation between the pressure prevailing in the fuel supply system and the loading state of the filter, the loading state is determined with high accuracy on the basis of the rotational speed of the fuel supply pump and the current flowing to the fuel supply pump.

[0069] FIG. 4 shows a flow chart for the method according to the invention. In block 30, a temporal progression of the rotational speed of the fuel supply pump is detected. In block 31, the detected values are compared, in entirety or in a selected form, with corresponding comparative values that have already been stored, in order to obtain a finding regarding the loading state on the basis of the deviation, such as the time difference.

[0070] FIGS. 1 to 4 are used for illustrating the inventive idea and are not limiting in character.

[0071] The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.