DEVICE FOR DETECTING THE STATE OF A FUEL INJECTOR

Abstract

A device comprises: an injector for injecting fuel into an engine combustion chamber, a switch formed by an injector housing and an injector nozzle needle and which changes its switching state depending on a closed or open state of the injector, an input line for supplying energy to an actuating element which adjusts the nozzle needle in its two states, an output line for conducting energy away from the actuating element, and an evaluation unit for detecting the switching state of the switch, wherein a first switch contact of the switch is connected to an electrical input line of the injector, a second switch contact of the switch is connected to ground, and the evaluation unit is configured to carry out a signal measurementon the input line and/or an output line to conclude a switch state.

Claims

1. A device for detecting a state of a fuel injector, the device comprising: an injector for injecting fuel into an engine combustion chamber, a switch which is formed by an injector housing and an injector nozzle needle and changes its switching state depending on a closed or open state of the injector, an input line for supplying energy to an actuating element which adjusts the injector nozzle needle in its two states, an output line for conducting energy away from the actuating element, and an evaluation unit for detecting the switching state of the switch, wherein a first switch contact of the switch is connected to an electrical input line of the injector, a second switch contact of the switch is connected to ground, and the evaluation unit is configured to carry out a signal measurement in order to conclude a switch state, comprising a signal filter comprising only passive components and connected between the evaluation unit and the input line and/or between the evaluation unit and the output line of the injector in order to emphasize a signal generated by switching the switch.

2. The device according to claim 1, further comprising an electronic control unit which comprises the evaluation unit, is connected by respective connections to the input line and the output line, and is configured to apply a higher voltage to the input line than to the output line for actuating the actuating element.

3. The device according to claim 1, wherein the first switch contact is connected to the input line of the injector via a resistor.

4. The device according to claim 1, wherein the second switch contact is connected to the same ground as an electrical circuit of the injector.

5. The device according to claim 1, wherein the injector and the switch are arranged in a common housing which comprises an input line, an output line and a ground connection.

6. The device according to claim 1, wherein the actuating element is a solenoid valve.

7. The device according to claim 1, wherein the evaluation unit performs the signal measurement either at the input line or the output line in order to conclude the switch state.

8. The device according to claim 1, wherein the passive components for forming the signal filter are resistors, capacitors, coils, oscillators or trimmers.

9. The device according to claim 1, wherein the signal filter comprises or is a pull-up resistor and/or a pull-down resistor in order to detect an absolute voltage at the input line or the output line.

10. The device according to claim 9, wherein the pull-up resistor leading from the input line or output line is connected to a supply voltage.

11. The device according to claim 1, wherein the signal filter is integrated in a cabling leading to the input line or in a cabling leading away from the output line.

12. The device according to claim 1, wherein the signal filter is arranged in an electronic control unit.

13. The device according to claim 1, wherein the injector is a common-rail injector.

14. An internal combustion engine comprising the device according to claim 1.

15. The device according to claim 2, wherein a voltage difference between input line and output line is 12V, 24V or 48V.

16. The device according to claim 4, wherein the ground is a body or an engine block of a vehicle.

17. The device according to claim 6, wherein the solenoid valve is configured to cause a change of state of the injector by raising or lowering the injector nozzle needle, which in turn causes a change of state of the switch.

18. The device according to claim 7, wherein the signal measurement of the evaluation unit takes place at the output line.

19. The device according to claim 11, wherein the cabling leading to the input line and/or the cabling leading away from the output line are arranged in a cable harness.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0035] Further features and details of the invention will become apparent from the following description of the figures, in which:

[0036] FIG. 1: shows a schematic depiction of a fuel injector with a state detection as known from the prior art,

[0037] FIG. 2: shows a schematic depiction of a fuel injector with a reduced number of connection lines and a state detection,

[0038] FIG. 3: shows an embodiment of the present invention in which a fuel injector for state injection is provided with a signal filter,

[0039] FIG. 4: shows an enlarged depiction of the signal filter, as used for example in FIG. 3,

[0040] FIG. 5: shows three different depictions for improving the signal to be detected by increasing the amplitude or making the leading edge steeper, and

[0041] FIG. 6: shows a filtering of the signal to be detected on the low-voltage side of an injector with a pull-up resistor.

DETAILED DESCRIPTION

[0042] FIG. 1 has already been explained in the introductory part of the description. Reference sign 2 shows there a fuel injector which has a total of four connection lines leading to the outside. The input line 4 in this case actuates an actuating element 8, which can lift a nozzle needle out of its nozzle needle seat. The output line 5 is also required there to close a circuit, so that the actuating element 8, which is configured as a coil, for example, can exert a magnetic force on the nozzle needle.

[0043] In order to now detect a state, i.e. whether the nozzle needle is in its nozzle needle seat, the nozzle needle together with the associated nozzle needle seat is used as a switch 3, wherein the two switch contacts (nozzle needle and nozzle needle seat) are each routed to the outside of the injector 2 via a separate line. The disadvantage of this is that separate lines are required to detect a switch state, which further increases the number of pins.

[0044] FIG. 2 shows a schematic depiction of a further developed injector 2 which has integrated state detection. The contacts of the switch 3 are not directly accessible here, since one pole of the switch 3 is connected to the input line 4 and the other pole of the switch 3 is routed to ground 10. This is usually implemented so that the injector 2 itself is connected to the ground 10 of the engine block. In normal operation, a voltage is applied to the actuating element 8, which is usually a solenoid valve, which causes a mechanical and/or hydraulic movement of the nozzle needle and thus opens the switch 3. When the voltage is removed, the switch 3 is closed again.

[0045] In order to be able to detect the switch state, the voltage or a very small voltage change at the injector contacts 4, 5 must be measured.

[0046] FIG. 3 shows a schematic structure of a device 1 according to the invention with an injector 2, a filter 7 and an evaluation unit 6, which can also be integrated in an electronic control unit (ECU). The injector 2 is operated via the two connections HS (high side) and LS (low side). In the energized state, a magnetic field is built up via the actuating element 8 and, with a delay, the opening delay, causes the nozzle needle to be lifted out of its nozzle needle set, thus triggering an injection. The injection is equivalent here to an opening of the switch 3. At the end of the current supply, the magnetic field is removed, whereupon the injection ends with a delay, the closing delay. This means a closing of the switch 3 in the injector 2. The signal at the input line 4 and the output line 5 is changed by the closing and the opening of the switch 3. This signal change can be detected by means of a voltage measurement in the evaluation unit 6. The change when the switch 3 is opened serves to determine the start of injection and the closing of the switch 3 indicates the end of the injection. The voltage only has to be measured at the output line 5 (or the LS) of the injector 2, which may mean no differential measurement is required, so that less complex evaluation units 6 can be used for a state detection. Since, as already explained in the introductory part, interference that can make level detection more difficult only cancels out with differential measurement, a measurement at only one contact, for example at the output channel 5, results in an overlapping of the useful signal with the interference. In order to filter this interference, the signal filter 7 is provided.

[0047] FIG. 4 shows a possible combination of components for improving the signal quality or filtering the desired signal. Passive components should be selected for this purpose in order to keep the control effort as low as possible. In FIG. 4, the filter 7 is applied by way of example on the low side, wherein it is clear to a person skilled in the art that a correspondingly modified filtering can also be applied on the high side if this is desired.

[0048] It can be seen that a pull-up resistor 11 is provided on the low side, i.e. on the output channel 5 of the injector, which connects the output channel 5 to the supply voltage Vcc. This allows a significantly higher signal amplitude to be achieved by filtering the useful signal, which can be seen in the left in FIG. 5, for example. An alternative to this can be found in the middle illustration, in which the useful signal is not boosted, but the magnitude of the carrier signal is reduced. This also thus results in a clear signal swing. The right-hand illustration in FIG. 5 contains a third variant for signal optimization, in which for example the amplitude is not increased, but a steeper edge rise is initiated during the switching process. Based on the control logic stored in the evaluation unit, one or a combination of the three methods shown in FIG. 5 can be effective in achieving the desired filtering of the target signal.

[0049] FIG. 6 shows the switching operations of the injector 2 and the associated change in voltage on the output line 5 or the low side. When the nozzle needle is lifted, the switch 3 opens and the contact via the internal resistor injector to ground is open-circuited. This raises the potential on the output line 5, where the signal swing is increased with the help of a resistor 11 that proceeds from said output line and leads to the supply voltage Vcc.

[0050] The resistance ratio of the described sides is determined by the evaluation unit 6 used, which can also be integrated in a control unit ECU. Limitations arise here due to the internal circuits in the control unit or the evaluation unit 6. Since the intended components of the filter 7 ultimately only work with ground 10 and supply voltage Vcc, no further source is necessary to implement the filter 7. This means that the filter can also be arranged in a cable harness and is therefore extremely easily retrofitted. If, on the other hand, there are evaluation units 6 or control units that can only carry out voltage detection in a certain voltage range, a suitable voltage splitter can be created in addition to the pull-up resistor 11 by means of a further resistor 12 that is connected to the ground 10 and proceeds from the output line 5. This configuration is shown in FIG. 4. If the switch 3 opens and the control element 8 is a coil, a defined voltage value is applied to the output channel 5 due to the voltage splitter consisting of the pull-up resistor 11 and the additional resistor 12.

[0051] Certain embodiments of the present invention improve the signal quality for a single-point measurement of an injector. In some embodiments, the single-point measurement allows simple adaptation to different control units from different manufacturers since most control units can monitor at least one contact for the control of the injector at its voltage level. In addition, certain embodiments can be realized in the control unit but can also be subsequently integrated into the cable harness if the control unit lacks internal resources. By combining these approaches, the signal-to-noise ratio can be increased, whereby a reliable status detection of the switching process can be realized even with a lower resolution of the voltage detection.

[0052] The use of passive components does not require any further voltages than those already present. This means that there is no additional outlay due to the additional provision of a stable control voltage, which would also have to be protected against interference. In an exemplary variant, it is sufficient to connect the LS contact to the supply voltage via a resistor 11 to increase the signal amplitude during the switching process.

[0053] In general terms, the circuit embodied in accordance with the invention uses a combination of passive components using supply voltage and ground.