DETERMINATION OF A POINT IN TIME OF A PREDETERMINED OPEN STATE OF A FUEL INJECTOR

Abstract

A method for determining the point in time of a predetermined open state of a fuel injector having a solenoid drive for a combustion engine of a motor vehicle. The method includes detection of a time profile of the current level of a current flowing through the solenoid drive during a boost phase, where the solenoid drive is subjected to a first voltage during a first part of the boost phase and a second voltage during a second part of the boost phase. The second voltage is selected so that the current level of the current flowing through the solenoid drive during the second part of the boost phase essentially remains unchanged, and determination of a point in time at which the detected time profile of the current level has an extreme value, where the determined point in time is the point in time of the predetermined open state.

Claims

1. A method for operating a fuel injector, comprising the steps of: providing a motor vehicle; providing a combustion engine, the combustion engine being part of the motor vehicle; providing a solenoid drive, the solenoid drive being part of the combustion engine; providing a boost phase; detecting a time profile of the current level of a current flowing through the solenoid drive during the boost phase; subjecting the solenoid drive to a first voltage during a first part of the boost phase; subjecting the solenoid drive to a second voltage during a second part of the boost phase; selecting the second voltage such that the current level of the current flowing through the solenoid drive during the second part of the boost phase remains substantially unchanged; determining a point in time at which the detected time profile of the current level has an extreme value, and the determined point in time is the point in time of a predetermined open state of a fuel injector.

2. The method of claim 1 further comprising the steps of providing the second voltage to lower than the first voltage.

3. The method of claim 1, further comprising the steps of ending the first part of the boost phase and beginning the second part of the boost phase when the current level of the current flowing through the solenoid drive reaches a predetermined value.

4. The method of claim 1, further comprising the steps of the current level of the current flowing through the solenoid drive reaching the predetermined value before a movement of an armature of the solenoid drive starts.

5. The method of claim 1, further comprising the steps of providing the first voltage to be approximately 65 Volts.

6. The method of claim 1, further comprising the steps of providing the second voltage to be between 25 Volts and 50 Volts.

7. The method of claim 1, further comprising the steps of providing the determined point in time of the predetermined open state of the fuel injector to be at least one of a start point in time or an end point in time of a fuel injector opening process.

8. The method of claim 1, further comprising the steps of: providing a reference point in time; determining a difference between the reference point in time and the determined the point in time of the predetermined open state of the fuel injector; and actuating the fuel injector; subjecting the solenoid drive to the first voltage pulse, such that the starting time of first voltage pulse and the time duration of the first voltage pulse is determined based on the determined difference.

9. The method of claim 1, further comprising the steps of: providing a reference point in time; determining a difference between the reference point in time and the determined the point in time of the predetermined open state of the fuel injector; and actuating the fuel injector; subjecting the solenoid drive to the first voltage pulse, such that the starting time of first voltage pulse is determined based on the determined difference.

10. The method of claim 1, further comprising the steps of: providing a reference point in time; determining a difference between the reference point in time and the determined the point in time of the predetermined open state of the fuel injector; and actuating the fuel injector; subjecting the solenoid drive to the first voltage pulse, such that the time duration of the first voltage pulse is determined based on the determined difference.

11. A computer program for determining the point in time of a predetermined open state of a fuel injector having a solenoid drive, the computer program stored in non-transitory memory and including instructions which, when executed by a processor, causes the processor to: detect a time profile of the current level of a current flowing through the solenoid drive during a boost phase; subject the solenoid drive to a first voltage during a first part of the boost phase; subject the solenoid drive to a second voltage during a second part of the boost phase; select the second voltage such that the current level of the current flowing through the solenoid drive during the second part of the boost phase remains substantially unchanged; determine a point in time at which the detected time profile of the current level has an extreme value, and the determined point in time is the point in time of a predetermined open state of a fuel injector.

12. The computer program of claim 11, wherein the second voltage to lower than the first voltage.

13. The computer program of claim 11, wherein the first part of the boost phase is ended and the second part of the boost phase is begun when the current level of the current flowing through the solenoid drive reaches a predetermined value.

14. The computer program of claim 11, wherein the current level of the current flowing through the solenoid drive reaches the predetermined value before a movement of an armature of the solenoid drive starts.

15. The computer program of claim 11, wherein the first voltage is approximately 65 Volts.

16. The computer program of claim 11, wherein the second voltage is between 25 Volts and 50 Volts.

17. The computer program of claim 11, wherein the determined point in time of the predetermined open state of the fuel injector to be a start or end point in time of a fuel injector opening process.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:

[0041] The FIGURE shows an example of a profile of voltage, current level and amount of fuel input as functions of time during the actuation of a fuel injector according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] 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.

[0043] Further advantages and features of the present invention arise from the following exemplary description of a preferred embodiment.

[0044] It is noted that the embodiment described below only represents a limited selection of possible versions of embodiments of the invention.

[0045] The FIGURE shows the profile of voltage 110, current level 120 and amount of fuel input 130 as functions of time t during the actuation of a fuel injector according to the invention, in particular during a boost phase B.

[0046] The boost phase B starts with a first part B1, in which the solenoid drive of the fuel injector is subjected to a first boost voltage U1. The first voltage U1 is significantly greater than the voltage of the vehicle battery and is for example approx. 65 V. During the first part B1 of the boost phase B, the current level 120 of the current flowing through the solenoid drive increases strongly and reaches a predetermined maximum value (peak current) 122 at the end of the first part B1 of the boost phase B. At this point in time, the second part B2 of the boost phase B starts, and the solenoid drive of the fuel injector is now subjected to a second boost voltage U2, which is somewhat lower than U1, for example in the region of 25V to 50V. The second boost voltage U2 is selected so that the profile of the coil current 120 during the second part B2 of the boost phase B is essentially horizontal, i.e. the coil current 120 essentially remains constant. Thus, significant changes in the motion inductance cause significant detectable changes in the coil current 120, as has been described above.

[0047] Shortly after the start of the second part B2 of the boost phase B, the actual opening process of the fuel injector starts and the amount of fuel input 130 starts to rise, as seen at 132. The end of the opening process ends at 134, where the amount of fuel input 130 reaches the maximum value thereof. The maximum value is maintained until the start of a subsequent closing process.

[0048] The profile of the current level 120 is sampled and mathematical and/or numerical methods are used to identify extreme values. As the current graph 120 shows, despite the essentially constant current value during the second part B2 of the boost phase B there is a local minimum in the current level 120 both at the start 132 and at the end 134 of the opening phase. The minima are detected and associated with the start 132 and the end 134.

[0049] The engine control unit now compares the detected points in time with reference values and determine whether corrections are necessary in order to achieve the specified injection amounts. Depending on the result of this comparison, the engine control unit then corrects the start time and/or time duration of the actuation. If the point in time of opening is shifted, the engine control unit shifts the start of the actuation accordingly, and if the point in time of the end of the opening is shifted, the engine control unit adjusts the injection duration accordingly.

[0050] The corrections are advantageously carried out pulse-specifically. Furthermore, during the correction, further physical system parameters may be taken into account, such as for example fuel temperature and the time since the previous injection. The corrections may advantageously be stored in the control unit for this as pilot control characteristic curves/fields or calculated using a suitable model.

[0051] 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.