Device for detecting the state of a fuel injector

Abstract

The device for detecting the state of a fuel injector according to the invention comprises: an injector for injecting fuel into an engine combustion chamber; a switch formed by the housing of the injector and the injector nozzle needle, the switch changing its switching state depending on the closed or open state of the injector; an input line for supplying energy to an adjusting element, the adjusting element adjusting the nozzle needle to its two states; an output line for conducting energy from the adjusting element; and an evaluation unit for detecting the switching state of the switch, wherein a first switching contact of the switch is connected to an electrical input line of the injector, a second switching contact of the switch is connected to ground, and the evaluation unit is designed to perform a signal measurement, in particular a voltage measurement at the input line and / or the output line, in order to infer the switching state. The invention is unique in that a signal filter is provided, which comprises only passive components and is connected between the evaluation unit and the input line and / or between the evaluation unit and the output line of the injector to emphasize the signal generated by switching the switch.

Description

Technical Field

[0001] The invention relates to a device for detecting the state of a fuel injector. Background Art

[0002] Nozzles or injectors are usually used to inject fuel into the combustion chamber of an engine. In this case, it is advantageous for an engine having such an injector if a control device is informed of the exact opening time of said injector, so that for example the tolerance range of the fuel injection quantity delivered by the injector is particularly narrow, which is also advantageous for the overall product life of the injector.

[0003] Furthermore, if the exact time at which an injector injects fuel is known, various control or monitoring functions of the engine are facilitated.

[0004] According to the prior art, it is known to use an electrical switch formed by a nozzle needle and an injector housing to detect the state of an injector. When the injector is not energized and the nozzle needle of the injector has not moved out of the nozzle needle seat in the injector housing, the switch is closed to ensure that no fuel escapes from the injector. As soon as the nozzle needle moves out of the nozzle needle seat, there is no longer an electrically conductive connection between them, so the electrical switch changes its state, i.e. becomes open. The switch changes its state again when the nozzle needle moves back into the nozzle needle seat, because this creates an electrically conductive connection, and the switch formed by the components goes into the closed state.

[0005] In the simplest form of state detection of the injector, a total of four lines are introduced into the injector housing, in which the switch is also arranged. Two lines are provided for the injector itself, and the other two lines are assigned to the switch. However, this has the disadvantage that the wiring effort required for a unit designed in this way is high.

[0006] If a 3-pole or 4-pole plug is used, i.e. 3 or 4 lines are extended to the injector via the switch, no additional work is required for the detection circuit. On the other hand, this means that the injector requires additional work due to the multiple components and the larger size of the connection assembly. A 4-line configuration such as Figure 1 shown.

[0007] In a modification of this type, which is also known in the prior art, the switch contacts are arranged in a manner that is not directly accessible or isolated in the housing of the injector. Figure 2 Here, one pole of the switch is connected to a pin on the injector or to the solenoid valve that drives the injector through a resistor. The other pole of the switch is also connected to the injector housing. In this case, the injector itself is usually connected to ground, which can be the engine block when used in a vehicle. In such a solution, there are only two cables or wires leading out of the housing.

[0008] In normal operation, a voltage is applied to the injector or to the solenoid valve that operates the injector, thereby triggering a mechanical and / or hydraulic movement of the nozzle needle. The nozzle needle is raised or lowered to open or close the switch again. For example, the switch can be closed by removing the voltage.

[0009] The problem with this state detection is that there may be an indefinite time delay between the application and removal of voltage to the injector or solenoid valve and the switch release (i.e. the movement of the nozzle needle from its valve seat or back to its valve seat), namely the so-called opening delay when the voltage is applied and the closing delay when the voltage is removed, because the mechanical and / or hydraulic movement of the nozzle needle has a certain inertia. In the case of an opening delay, the switch opens only after the voltage is applied. Due to this opening delay, the energization may have ended while the switch is still open. In the case of a closing delay, the switch closes only after the energization has ended with a certain delay.

[0010] Despite the above-mentioned disadvantages, it is reasonable to measure the voltage applied to the input and / or output lines to detect the switch state, because this allows conclusions to be drawn about the injection state or the closed state of the injector. It must be taken into account here that the switch cannot be loaded with high currents and is limited to a few mA by resistors for efficiency reasons.

[0011] In the energized state, the coil (usually the regulating element of the nozzle needle) generates a magnetic field and causes delayed injection, that is, opening delay. This injection is equivalent to opening the switch. At the end of the energization, the magnetic field degenerates and then ends the injection in a delayed manner, that is, closing delay. This means closing the switch in the injector.

[0012] By closing and opening the switch, the signal of the voltage side contact (high voltage side HS) and the low voltage side contact (low voltage side LS) changes. This signal change can be detected by voltage measurement in the evaluation unit.

[0013] The change when the switch is open is used to determine the start of injection, and the closing switch indicates the end of injection.

[0014] Since the evaluation unit for such state detection is usually located in the control device of the engine, the so-called ECU (electronic control unit), it is advantageous that the signal detection of the injector is compatible with a large number of ECUs on the market. However, since the pins of the ECU only partially allow voltage measurement on the output side or input side of the injector, it is advantageous to implement such a state detection and thus voltage measurement only on one contact of the injector. Here, the low voltage side LS is preferably selected.

[0015] Since interference influences from external input can only be offset by more complex differential measurements, there is a superposition of effective signals and interference during the measurement of only one contact, which makes it more difficult to detect the voltage signal associated with the switch state change. Summary of the invention

[0016] The object of the present invention is therefore to overcome the above-mentioned disadvantages of the prior art and to provide a device for detecting the state of an injector which is more advantageous than the known prior art.

[0017] This is achieved by a device according to an aspect of the invention.An advantageous embodiment is another aspect of the invention.

[0018] The invention enables clear detection of the state of the switch in a noisy environment causing fluctuations in the signal to be detected. In addition, the invention also makes it possible to operate the injector using only two line cables. In the case of state detection, a third or even a fourth line cable is not required.

[0019] The device for detecting the state of a fuel injector according to the invention comprises: an injector. It is used to inject fuel into the combustion chamber of the engine; a switch formed by the injector housing and the injector nozzle needle, the switch changing its switching state depending on the closed or open state of the injector; an input line for supplying energy to an adjusting element, the adjusting element adjusting the nozzle needle to its two states; an output line for conducting energy from the adjusting element; and an evaluation unit for detecting the switching state of the switch, wherein a first switching contact of the switch is connected to an electrical input line of the injector, a second switching contact of the switch is connected to ground, and the evaluation unit is designed to perform signal measurements, in particular voltage measurements at the input line and / or the output line, in order to infer the switching state. The uniqueness of the invention lies in the provision of a signal filter, which comprises only passive components and is connected between the evaluation unit and the input line and / or between the evaluation unit and the injector output line to emphasize the signal generated by switching the switch.

[0020] According to an optional improvement, the injector also has an electronic control unit including the evaluation unit, which is connected to the input line via a first connection and to the output line via a second connection, and provides a higher voltage, in particular a power supply voltage, to the input line than to the output line for driving the adjustment element, wherein the voltage difference between the input line and the output line is preferably 12V, 24V or 48V.

[0021] Furthermore, according to the invention it can be provided that the first switch contact is connected to the input line of the injector via a resistor. This results in a voltage change being detected when the switch is closed and opened.

[0022] According to a further development of the invention, it can be provided that the second switch contact is connected to the same ground as the circuit controlling the injector, the ground preferably being the body or the engine block of the vehicle.

[0023] Furthermore, according to the invention it can be provided that the injector and the switch are arranged in a common housing which comprises input lines, output lines and a ground connection and preferably has no further connections for electrical signals.

[0024] According to an optional development of the invention, it can be provided that the adjusting element is a solenoid valve which is preferably designed to bring about a change in the state of the injector and thus of the state of the switch by raising or lowering the nozzle needle.

[0025] Furthermore, according to the invention, the evaluation unit can perform a signal measurement, in particular a voltage measurement, at the input line or at the output line in order to derive the switch state, wherein the signal measurement of the evaluation unit preferably takes place at the output line.

[0026] The input line may be HS, ie, a line to which a high voltage is applied, and the output line may be a low voltage side LS, ie, a line to which a low voltage is applied. The current is controlled by HS.

[0027] According to the invention, it can be provided that the passive components for forming the signal filter are resistors, capacitors, coils, oscillators or trimming capacitors. The advantage here is that the combination of passive components does not require voltage levels other than the existing voltage (e.g. the supply voltage). No additional effort is required due to the generation of a stable control voltage. This is especially true because this must also be protected against interfering influences.

[0028] According to an optional further embodiment, it can be provided that the signal filter comprises a pull-up resistor and / or a pull-down resistor for amplifying the voltage change detected by the evaluation unit. By providing the pull-up resistor and / or the pull-down resistor, the signal level generated by the switching of the switch can be increased. Since the interference on the line to be tested does not increase accordingly, the SNR (signal-to-noise ratio) increases, so that the switching state of the switch and thus the switching state of the test injector can be detected more reliably.

[0029] In this case, a pull-up resistor from the input line or the output line may be connected to a power supply voltage so that, for example, opening the switch using the pull-up resistor arranged in the output line causes the signal level to increase to the level of the power supply voltage.

[0030] If this level is too high for the evaluation unit to detect, a voltage divider can be formed by a further resistor to ground, which is connected in series with the pull-up resistor and, by appropriately sizing the resistor values, the desired voltage level can be achieved when the switch is opened.

[0031] According to the invention, it can also be provided that the signal filter is integrated in the cabling leading to the input line or in the cabling leading away from the output line, preferably arranged in a cable harness.

[0032] Since the signal filter can be arranged in a cable harness or in a corresponding cabling of an input or output line, a filter can also be integrated subsequently, so that the injector does not have to be replaced.

[0033] It can also be provided that the signal filter is arranged in an electronic control unit, wherein not every control unit has the capability to switch or subsequently add a signal filter. It is therefore sometimes advantageous if the signal filter consists only of passive components and can also be arranged in the cabling.

[0034] According to the invention, it can be provided that the injector is a common rail injector.

[0035] The invention also relates to an internal combustion engine having a device according to one of the above-described variants. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Further advantages, features and details of the present invention will become apparent from the following description of the drawings. The drawings show:

[0037] Figure 1 A schematic diagram showing a fuel injector with state detection known in the prior art,

[0038] Figure 2 A schematic diagram showing a fuel injector with fewer connecting lines and with state detection,

[0039] Figure 3 An embodiment of the invention is shown in which a fuel injector for state injection is equipped with a signal filter,

[0040] Figure 4 Shown as Figure 3 A magnified schematic diagram of the signal filter used in

[0041] Figure 5 Three different schematic diagrams showing how to improve the signal to be detected by increasing the amplitude or making the leading edge steeper, and

[0042] Figure 6 Filtering of the signal to be detected on the low voltage side of the injector with a pull-up resistor is shown. DETAILED DESCRIPTION

[0043] Figure 1 This has already been explained in the background section of the description. A fuel injector is shown which has a total of four connecting lines leading outward. In this case, the input lines control an actuating element which can lift the nozzle needle out of the nozzle needle seat. In order to close the circuit, an output line is also required so that the actuating element, which is designed, for example, as a coil, can generate a magnetic force on the nozzle needle.

[0044] In order to detect whether the nozzle needle valve is in its nozzle needle valve seat, the nozzle needle valve and its associated nozzle needle valve seat are used together as a switch, wherein the two switching contacts (nozzle needle valve and nozzle needle valve seat) are respectively led out to the outside of the injector through separate lines. The disadvantage of this is that a separate line is required to detect the switching state, which further increases the number of pins.

[0045] Figure 2 Schematic diagram of an improved injector with integrated status detection. The contacts of the switch are not directly accessible, since one pole of the switch is connected to the input line and the other pole of the switch is connected to ground. This is usually implemented in that the fuel injector itself is connected to the ground of the motor block. In normal operation, voltage is applied to the regulating element (usually a solenoid valve), which leads to a mechanical and / or hydraulic movement of the nozzle needle, thereby opening the switch. By removing the voltage, the switch is closed again.

[0046] In order to be able to detect the switching state, the voltage or a very small voltage change must be measured at the fuel injector contacts.

[0047] Figure 3The schematic structure of the device according to the invention is shown, which has an injector, a filter and an evaluation unit, which can also be integrated into an electronic control unit (ECU). The injector is operated via two connections HS (high voltage side) and LS (low voltage side). In the energized state, a magnetic field is established by the regulating element, which has a delay, namely the opening delay, and lifts the nozzle needle from the nozzle needle seat, thereby triggering the injection. In this case, the injection is equivalent to opening the switch. After the end of the energization, the magnetic field disappears, and the injection is then ended with a delay, namely the closing delay. This means that the switch in the injector is closed. By closing and opening the switch, the signal at the input line and at the output line changes. This signal change can be detected by voltage measurement in the evaluation unit. The change when the switch is opened is used to determine the start of injection, and the end of injection is indicated when the switch is closed. It is advantageous here that the voltage only needs to be measured at the output line (or LS) of the injector, because this does not require a differential measurement, so a less complex evaluation unit can be used for state detection. As mentioned in the background section, interference influences complicate level detection and can only be removed by differential measurement, whereby measurement at only one contact point, for example at an output channel, results in a superposition of the useful signal and interference influences. Signal filters are provided to filter these interference influences.

[0048] Figure 4 Possible combinations of components for improving signal quality or filtering the desired signal are shown. For this purpose, passive components must be selected in order to keep the control costs as low as possible. In the figure, the filter is used by way of example on the low voltage side, but it is clear to a person skilled in the art that a correspondingly modified filter can also be applied on the high voltage side if necessary.

[0049] It can be seen that the pull-up resistor is set on the low voltage side, that is, the output channel of the injector, and the resistor connects the output channel to the power supply voltage V CC . Therefore, by filtering the useful signal, significantly higher signal amplitudes can be achieved, such as Figure 5 An alternative to this approach is shown in the middle diagram, in which the useful signal does not rise, but the value of the carrier signal decreases. This also results in a clear signal rise (Signalhub). Figure 5 The right figure in Figure 1 includes a third variant of signal optimization, in which the amplitude is not increased, but a steeper leading edge rise is generated during the switching process. According to the control logic stored in the evaluation unit, Figure 5 One or a combination of the three methods shown in can effectively achieve the desired filtering of the target signal.

[0050] Figure 6The switching process of the injector and the associated change in the voltage on the output line or low voltage side are shown. When the nozzle needle is lifted, the switch is open and the contact from the injector to ground via the internal resistor is in an open circuit state. This increases the potential of the output line, which is increased by drawing the supply voltage V from the output line and introducing it. CC The resistor increases and the signal rises.

[0051] The resistance ratio of the two sides is determined by the evaluation unit used, which can also be integrated into the control unit ECU. Restrictions arise here due to the internal circuits in the control device or the evaluation unit. Since the filter setting components are ultimately connected only to ground and the supply voltage V CC The filter can therefore also be arranged in a cable harness and is therefore extremely easy to retrofit. If, on the other hand, an evaluation unit or control unit is present which can only perform voltage detection within a certain voltage range, a suitable voltage divider can be created by connecting ground and another resistor leading from the output line in addition to the pull-up resistor. This configuration is shown in Figure 4 If the switch is open and the regulating element is a coil, a defined voltage value is applied to the output channel due to the voltage divider consisting of the pull-up resistor and another resistor.

[0052] The invention has the advantage that it improves the signal quality of the single-point measurement of the injector. This is particularly advantageous because the single-point measurement allows easy adaptation to different control units from different manufacturers, since most control units can monitor at least one contact in order to control the injector at its voltage level. Furthermore, the proposed solution has the advantage that it can be implemented both in the control unit and subsequently integrated into the cable harness without control unit internal resources. By combining these methods, the signal-to-noise ratio can be increased, so that reliable state detection of the switching process can be achieved even with a lower voltage detection resolution.

[0053] Furthermore, the use of passive components does not require any voltage other than that already present, which is advantageous. This also avoids any additional effort due to the additional provision of a stable control voltage, which must also be protected against interference. In an exemplary variant, it is sufficient to connect the LS contact to the supply voltage via a resistor to increase the signal rise amplitude during the switching transition.

[0054] In the circuit according to the invention, a combination of passive components with supply voltage and ground is usually used.

Claims

1. A device for detecting the state of a fuel injector, wherein include: injectors, which are used to inject fuel into the engine combustion chamber; a switch formed by an injector housing and an injector nozzle needle valve, the switch changing a switching state of the switch according to a closed or open state of the injector; an input line for supplying energy to an adjusting element which adjusts the nozzle needle into its two states, an output line for conducting energy from the regulating element; as well as an evaluation unit for detecting a switching state of the switch, in A first switch contact of the switch is connected to an electrical input line of the injector; The second switch contact of the switch is grounded; as well as The evaluation unit is designed to perform a voltage measurement at the input line and / or the output line in order to infer a switch state; It is characterized in that 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 to emphasize the signal generated by switching the switch; an electronic control unit comprising the evaluation unit, the electronic control unit being connected to the input line and the output line via corresponding connections and being designed to supply a higher voltage to the input line than to the output line for driving the regulating element; wherein the first switch contact is connected to the input line of the injector only through a resistor; wherein the signal filter comprises a pull-up resistor and / or a pull-down resistor for detecting an absolute voltage at the input line or the output line, The pull-up resistor from the input line or the output line is connected to a power supply voltage (V CC ).

2. The device according to claim 1, wherein the electronic control unit is designed to provide a power supply voltage (V CC ). 3 . The device according to claim 1 , wherein a voltage difference between the input line and the output line is 12 V, 24 V, or 48 V.

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

5. The apparatus of claim 4, wherein the ground is a vehicle body or an engine block.

6. The apparatus of claim 1, wherein the injector and the switch are arranged in a common housing including input wires, output wires, and a ground connection.

7. The device according to claim 1, wherein the regulating element is a solenoid valve.

8. The device of claim 7, wherein the solenoid valve is designed to cause a change in the state of the injector by lifting or lowering the nozzle needle, thereby causing a change in the state of the switch.

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

10. The device according to claim 9, wherein the signal filter is arranged in a cable harness.

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

12. An arrangement according to any preceding claim, wherein the injector is a common rail injector.

13. An internal combustion engine having a device according to any one of the preceding claims 1 to 12.

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