Method for increasing the accuracy of pressure detection without using a sensor

Abstract

A method for determining a pressure value in a fluid conveying system of a motor vehicle, the vehicle having an actuable electric motor and having a fluid feed pump drivable by the electric motor, includes: determining a rotational speed of the electric motor; determining an actuation current of the electric motor; acquiring a pressure value as a function of the determined rotational speed and the determined actuation current of the electric motor; processing the acquired pressure value with at least one external state variable in a controller; and correcting the acquired pressure value.

Claims

1. A method for determining a pressure value in a fluid conveying system of a motor vehicle, the vehicle having an actuable electric motor and having a fluid feed pump drivable by the electric motor, the method comprising: determining a rotational speed of the electric motor; determining an actuation current of the electric motor; acquiring a pressure value as a function of the determined rotational speed and the determined actuation current of the electric motor; processing the acquired pressure value with at least one external state variable in a controller (18); and correcting the acquired pressure value based at least in part on the processing of the acquired pressure value with at least one external state variable.

2. The method as claimed in claim 1, further comprising adapting, by the controller (18), the actuation current of the electric motor as a function of the at least one external state variable and/or the acquired pressure value and/or the corrected pressure value.

3. The method as claimed in claim 1, wherein the at least one external state variable comprises a plurality of external state variables formed at least partially by measurement variables and/or calculated variables from other controllers and/or sensors of the motor vehicle.

4. The method as claimed in claim 1, wherein the at least one external state variable comprises a plurality of external state variables and the external state variables originate from models (9), wherein different external state variables can be output by the models (9) as a function of predefinable input variables.

5. The method as claimed in claim 4, wherein the models (9) from which the external state variables originate corresponds to a characteristic diagram stored as an emergency running program for the motor vehicle.

6. The method as claimed in claim 5, wherein each model (9) is used to infer unknown variables from known variables, and wherein each model (9) has empirically acquired data records and/or data records acquired by simulation, to determine the unknown variables.

7. The method as claimed in claim 3, further comprising comparing the acquired pressure value with the external state variables to determine a limitation of a working range of the fluid conveying system.

8. The method as claimed in claim 7, further comprising calibrating the fluid conveying system based on the comparison of the external state variables with the acquired pressure value.

9. The method as claimed in claim 1, wherein the acquiring of the pressure value is performed as a function of at least one directly input external state variable.

10. The method as claimed in claim 1, further comprising determining an internal state variable of the fluid conveying system indirectly as a function of the at least one external state variable.

11. The method as claimed in claim 1, wherein the acquired pressure value corresponds to the pressure in the fluid to be conveyed at an output of the fluid feed pump and/or at a location downstream of the fluid feed pump and/or at a location upstream of the fluid feed pump.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

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

(2) FIG. 1 shows a flowchart illustrating the method according to an embodiment of the invention; and

(3) FIG. 2 shows a block diagram which shows, for example, the structure of a model in a simulation program, the transition from external state variables from a vehicle-side model into a controller used to determine the pressure value is shown here.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

(4) FIG. 1 shows a flowchart 1 that illustrates the method according to an embodiment of the invention. In block 2, the rotational speed of the electric motor that drives the fuel feed pump is detected. In block 3, the actuation current of the electric motor is detected. Both detection operations can take place in a variety of ways by known methods.

(5) In block 4, a pressure value is acquired on the basis of the acquired rotational speed and the acquired actuation current of the electric motor. This pressure value represents the pressure in the fuel which is to be conveyed. Subsequently, in block 5 the acquired pressure value is processed with at least one external state variable. In this context, the processing can take place in a variety of ways. In addition to an offsetting, it is also possible to compare the values or to carry out a correction. The type of processing with the acquired pressure value can vary depending on the external state variable that was used.

(6) Finally, in block 6 the pressure value is corrected. In this context, the previously acquired pressure value is corrected as a function of the processing with the external state variables. The corrected pressure value can then be used again as a basis for further calculations or processing operations. In particular, selective adaptation of the actuation current of the electric motor can take place in order to change the delivery capacity of the fuel feed pump.

(7) The arrow 7 stands symbolically for the passing on of the corrected pressure value to, for example, a further controller. Alternatively, the arrow 7 can also stand for an adapted actuation of the electric motor that has taken place as a function of the corrected pressure value. As a result, a fuel conveying operation that is better adapted to the given boundary conditions can be achieved by the fuel feed pump.

(8) FIG. 2 shows a schematic overview 8 in the form of a block diagram. FIG. 2 illustrates a block 9 which corresponds to a model such as can be stored in the vehicle, for example in a controller. The block 9 stands symbolically for this model.

(9) Within the block 9, the blocks 10, 11, 12, 13, 14 and 15 are illustrated. These blocks 10 to 15 stand for individual input variables, which can be read into the model 9. The input variables can be formed, as already illustrated in the preceding part of the description, by a wide variety of values, inter alia measured values of sensors or calculated values. Examples here are values such as the rotational speed of the motor, the fuel consumption, the external temperature, the temperature of the fuel high pressure pump or the quality of the fuel.

(10) The input variables are processed within the model 9. These include, in particular, weightings and calculations. The individual values are combined in the bar 16 and passed on individually in a selected form or as a combined signal to the block 18 along the signal conduction path 17.

(11) The block 18 symbolizes a controller that actuates the electric motor of the fuel feed pump. Further state variables or external requirements can also be fed into this controller 18 via the signal line 19. For example the processing of the acquired values for the actuation current of the electric motor and the value of its rotational speed with one or more of the external state variables takes place within the controller 18. Finally, a control signal is fed back to the electric motor from the controller 18, as a result of which the rotational speed of the electric motor can be adapted.

(12) FIGS. 1 and 2 do not have a restrictive character and serve to clarify the inventive concept.

(13) 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.