Device for sensing the state of an injector

Abstract

The invention relates to a device for sensing the state of an injector, comprising an injector for injecting fuel into an engine combustion chamber, a switch, which is designed to change the switching state thereof in accordance with the state of the injector, and an evaluating unit for sensing 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 evaluating unit is designed to carry out a first current measurement for a current flowing into the injector and into the switch and a second current measurement for the current flowing into the injector.

Claims

1. A device for state detection of an injector comprising: an injector for injecting fuel into an engine combustion chamber; a switch that is adapted to change its switch state in dependence on a state of the injector; and an evaluation unit for detecting the switch state of the switch, wherein a first switch contact of the switch is connected to an electrical input line of the injector; and a second switch contact of the switch is connected to ground, and the evaluation unit is adapted to carry out a first current measurement for a current (I.sub.HS, I.sub.CT) flowing into the injector and into the switch and a second current measurement for the current (I.sub.LS) flowing into the injector.

2. The device in accordance with claim 1, wherein the evaluation unit is further adapted to determine the switch state of the switch based on a difference of the measured values between the first current measurement and the second current measurement.

3. The device in accordance with claim 1, wherein the injector is adapted to change between an injection state and a closed state; and wherein the switch adopts a first switch state on the injection state of the injector and a second switch state on the closed state of the injector.

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

5. The device in accordance with claim 1, wherein the second switch contact is connected to the same ground as a current circuit of the injector and the ground is the body or an engine block of a vehicle.

6. The device in accordance with claim 1, wherein the evaluation unit further comprises a filter to filter a difference of the two measured values obtained by the first current measurement and the second current measurement.

7. The device in accordance with claim 1, wherein the injector and the switch are arranged in a common housing that comprises an input line, an output line, and a connection to ground.

8. The device in accordance with claim 7, wherein the first current measurement of the evaluation unit is arranged at the input line and the second current measurement of the evaluation unit is arranged at the output line of the housing.

9. The device in accordance with claim 7, wherein the ground is connected to the second contact of the switch.

10. The device in accordance with claim 1, wherein the injector is a solenoid valve injector in which a solenoid valve is adapted to initiate a state change of the injector that in turn also effects a state change of the switch.

11. The device in accordance with claim 1, wherein the switch changes its state due to a movement of an injector component.

12. The device in accordance with claim 1, wherein the injector is a common rail injector.

13. A method for state detection of an injector for injecting fuel into an engine combustion chamber, the method comprising: performing a first current measurement to measure a sum of a current (I.sub.HS) flowing into the injector and a current (I.sub.CT) flowing into a switch, the switch adapted to change its switch state in dependence on a state of the injector; measuring only current (I.sub.LS) flowing through the injector by a second current measurement; and drawing a conclusion on the current (I.sub.CT) actually flowing through the switch from a difference of the first current measurement from the second current measurement.

14. The method in accordance with claim 13, wherein a result of the difference of the first current measurement from the second current measurement is subjected to a filtering.

15. An internal combustion engine having the device in accordance with claim 1.

16. The device in accordance with claim 11, wherein the switch changes its state due to a movement of a valve needle of the injector.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Further advantages, features, and details of the present invention will become clear on the basis of the following description of the Figures. There are shown:

(2) FIGS. 1-3: schematic representations to explain the already known prior art;

(3) FIG. 4: a schematic representation of the device in accordance with the invention;

(4) FIG. 5: a first specific embodiment of the present invention in a schematic representation; and

(5) FIG. 6: a second specific embodiment of the present invention in a schematic representation.

DETAILED DESCRIPTION

(6) FIGS. 1 to 3 were already explained in the introductory part of the description. In this respect, reference numeral 2 shows an injector that closes or opens a switch 3 on a change of its state. A first contact of the switch 3 is here connected to one of the two lines emanating from the injector 2 via a resistor 6. This has the result that on a closed state of the switch 3, a current flows through the resistor 6 that flows to ground 5 via the housing 8 of the device.

(7) Exemplary values for the flowing current are drawn in FIG. 2 and FIG. 3. FIG. 2 thus shows the state in which the injector 2 is not energized, but the switch 3 is in a closed state. A current of 10 mA accordingly flows through the switch 3 by a corresponding design of the resistor 6.

(8) In contrast, FIG. 3 shows the state in which the injector 2 is energized and the switch 3 is also closed. It can be recognized that 10 A also flow through the injector 2 in addition to the 10 mA that flow through the resistor 6 and the switch 3 to ground 5. If information were now required on the switch state, it was usual in the prior art to determine the inflowing current that is a combination of current flowing through the switch and current flowing through the injector 2. The disadvantages discussed in more detail in the introductory part of the description result in this respect.

(9) FIG. 4 shows a schematic representation of the present invention. The device 1 in this respect has an injector 2 that is suitable to discharge fuel into a combustion chamber in a metered manner. For this purpose, the injector 2 can adopt a first state in which no fuel exits and a second state in which fuel is discharged. If the injector 2 is in the second state in which fuel is discharged, a switch 3 is closed. Since a first contact 31 of the switch 3 is connected to a current supply line 21 of the injector 2 via a resistor 6, a current flow results from the energy source of the device 1 in the direction of ground 5 and runs through the switch 3. The second contact 32 of the switch 3 is connected to ground 5 via connection 83. The connection 83 can here take place via the housing 8 of the device 1 that is connected to ground 5. It is thus not necessary that a further line has to be provided that is led out of the housing 8. This improves the handling of the device 1 and reduces the number of components susceptible to error. The second contact 32 of the switch 3 is here only connected to the outer housing 8 of the device 1.

(10) Two lines 81, 82 run from the housing 8, with the first line 81 having a branch to the resistor 6 between the housing 8 and the current input of the injector 2. The second line 82 running out of the housing 8 here connects the ground 5 to the current output of the injector 2.

(11) A respective current measurement 41, 42 is furthermore provided at these two lines 81, 82. The results of the two current measurements 41, 42 are supplied to a difference module 43 that outputs the amount of the difference of the two measured values as the result. It is thereby possible that the relatively small current that flows through the switch 3 can be simply detected on a presence of noise or other superpositions on the current.

(12) Provision can also be made that the evaluation unit 4 is integrated in the housing 8.

(13) FIG. 5 shows a specific implementation of the present invention. The current here is output, starting from a control logic 9, in the direction of an injector, that for reasons of simplicity is shown as an injector coil 23 in the present case, and of the resistor 6. Before a division of the current into the current through the resistor in the direction of ground 5 and the current through the injector coil 23 in the direction of ground 5, the current is measured with the aid of a shunt resistor 411 and an operational amplifier 412. This first current measurement 41 here measures both the current I.sub.CT flowing through the resistor 6 and the current I.sub.HS flowing through the injector.

(14) The second current measurement 42 here likewise takes place with the aid of a shunt resistor 421 in which the current flowing therethrough is determined by a further operational amplifier 422. The two operational amplifiers 412 and 422 here have the same amplification factors k. In addition, the two outputs of the operational amplifiers (OPV) 412 and 422 are given to a difference module 43. It is thus possible to determine the voltage difference of the voltage dropping over the two shunt resistors 411 and 421 and to forward its difference to a filter 7. Since the voltage that drops over the shunt resistors 411 and 421 and that is amplified by the factor k by the two OPVs 412 and 422, is substantially proportional to the current flowing through the shunt resistor, a measure thus results for the current flow in which the respective shunt resistor 412 and 422 is positioned.

(15) FIG. 6 shows a further embodiment of the invention with a transformer. A transformer 423 can also be used as an alternative to the measurement by operational amplifiers 412 and 422. This only works with alternating current, but is also able to detect the time of the switch actuation of the switch 3. In this respect, the polarity of the impulse from the transformer 423 would indicate the opening or closing of the switch 3.

(16) The general functional principle of the schematic implementation shown in FIG. 6 here does not differ from the solutions described in detail above so that a detailed description can be dispensed with.

(17) It is additionally clear to the skilled person that a detection can be performed by a plurality of different circuits of which only a few very specific ones have been shown.

(18) If the injector is not energized, the detection does not work. For example when all the currents have already decayed, but the injector is still open due to the inertia. The closing time would not be able to be detected in such a case.

(19) This can be solved in that a small current is fed from the onboard network voltage into the injector via a resistor on the injector line to which the resistor is connected. A current of a few mA is likewise sufficient in this respect that flows permanently as an “offset current” and thus also enables a detection at any time, even if the injector is not even controlled.