Drive circuit for an injector arrangement and a diagnostic method

Abstract

The invention relates to a drive circuit for an injector arrangement comprising a fuel injector, and method of detecting faults in the drive circuit. The drive circuit comprises diagnostic means (RH, RL) that is operable to sense a measured voltage (VBIAS) between the injector and a known voltage level (VBAT, VGND). The measured voltage (VBIAS) is biased with respect to the known voltage (VBAT, VGND) to a predicted voltage (VPinjN, VBcalc) unless the drive circuit has a fault. A fault signal is provided on sensing of a measured voltage (VBIAS) that differs from the predicted voltage (VPinjN, VBcalc). The drive circuit may additionally, or alternatively, comprise diagnostic means (RF). The diagnostic means (RF) is operable to sense a detected current (Idect) and to provide a fault signal on detection of a fault, when the detected current (Idect) is at variance from a threshold current (Itrip).

Description

FIGURES

Preferred embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a block diagram illustrating a drive circuit for controlling a piezoelectric fuel injector arrangement in an engine;

FIG. 2 is a circuit diagram illustrating the piezoelectric drive circuit in FIG. 1;

FIG. 3 is a circuit diagram as shown in FIG. 2, having a first diagnostic tool (a resistive bias network) according to a first embodiment of the present invention and a second diagnostic tool (a fault trip circuit) according to a second embodiment of the present invention;

FIG. 4 is the circuit diagram of FIG. 3, configured to detect an injector with an open circuit fault using the resistive bias network;

FIG. 5 is a schematic representation of a voltage waveform across a bank of injectors, illustrating the timing of the use, in an injection cycle, of the resistive bias network shown in FIG. 3;

FIG. 6 is a flow diagram of a diagnostic method using the resistive bias network shown in FIG. 3 whilst the drive circuit is in operation;

FIG. 7 is a flow diagram of a diagnostic method of using the resistive bias network shown in FIG. 3 when the injector arrangement is at start-up;

FIG. 8 is a circuit diagram illustrating a drive circuit shown in FIG. 3 with the fault trip circuit having a discharge switch closed, and having residual charge on a fuel injector, in order to detect a low side to ground potential short circuit fault;

FIG. 9 is a circuit diagram illustrating the drive circuit shown in FIG. 3 with the fault trip circuit having an injector selector switch closed in order to detect a high side to ground potential short circuit fault;

FIG. 10 is a circuit diagram illustrating the drive circuit shown in FIG. 3 with the fault trip circuit having a charge switch closed in order to detect a high side to ground potential short circuit fault;

FIG. 11 is a circuit diagram illustrating the drive circuit shown in FIG. 3 with the fault trip circuit having the charge switch closed in order to detect a low side to ground potential short circuit fault;

FIG. 12 is a circuit diagram illustrating the drive circuit shown in FIG. 3 with the fault trip circuit having a regeneration switch closed in order to detect a high side to ground potential short circuit fault;

FIG. 13 is a circuit diagram illustrating the drive circuit shown in FIG. 3 with the fault trip circuit having a regeneration switch closed and having no or negligible charge on the injector, in order to detect a low side to ground potential short circuit fault; and

FIG. 14 is a flow diagram of a diagnostic method of using the fault trip circuit shown in FIGS. 8 to 13, which is used when the injector arrangement is at start-up.

Claims

1. A drive circuit for an injector arrangement comprising a fuel injector, the drive circuit comprising a diagnostic tool (RH, RL) operable: a) to sense a measured voltage (VBIAS) between the injector and a known voltage level (VBAT, VGND), the measured voltage (VBIAS) being biased with respect to the known voltage (VBAT, VGND) to a predicted voltage (VPinjN, VBcalc) unless the drive circuit has a fault; andb) to provide a fault signal on sensing of a measured voltage (VBIAS) that differs from the predicted voltage (VPinjN, VBcalc).

2. A drive circuit as claimed in claim 1, the drive circuit further comprising a selector switch arrangement (SQ1, SQ2) operable to select the fuel injector into the drive circuit and to deselect the fuel injector from the drive circuit.

3. A drive circuit as claimed in claim 2, wherein the predicted voltage (VBcalc) is the voltage between the fuel injector and the known voltage level (VBAT, VGND) when the injector is deselected from the drive circuit.

4. A drive circuit as claimed in claim 2, wherein the predicted voltage (VPinjN) is substantially the sum of the known voltage (VBAT, VGND) and a voltage (VPinjN) across the fuel injector when the fuel injector is selected in the drive circuit.

5. A drive circuit as claimed in claim 2, wherein the selector switch arrangement (SQ1, SQ2) is operable prior to detection of a fault.

6. A drive circuit as claimed in claim 1, wherein the signal is provided if the measured voltage (VBIAS) is outside a tolerance voltage (VBtol) of the predicted voltage (VBcalc, VPinjN).

7. A drive circuit as claimed in claim 1, wherein the measured voltage (VBIAS) is sensed across part of a potential divider connected to the injector and the known voltage (VBAT, VGND).

8. A drive circuit as claimed in claim 1, wherein the drive circuit further comprises a further diagnostic tool (RF) in a connection of the drive circuit to a ground potential (VGND), the further diagnostic tool (RF) being operable: a) to sense a detected current (Idect); andb) to provide a signal on detection of a fault, wherein the signal is provided when the detected current (Idect) is at variance from a threshold current (Itrip).

9. A drive circuit as claimed in claim 1, further comprising: i) a first charge storage device (C1) for operative connection with the fuel injector during a charging phase so as to cause a charge current to flow therethrough;ii) a second charge storage device (C2) for operative connection with the fuel injector during a discharge phase so as to permit a discharge current to flow therethrough; andiii) a switch arrangement (Q1, Q2) for operably controlling the connection of the fuel injector to the first charge storage device (C1) or the second charge storage device (C2).

10. A drive circuit as claimed in claim 9, wherein the switch arrangement comprises a charge switch (Q1) operable to close so as to activate the charging phase.

11. A drive circuit as claimed in claim 9, wherein the switch arrangement comprises a discharge switch (Q2) operable to close so as to activate the discharge phase.

12. A drive circuit as claimed in claim 9, further comprising a power supply and regeneration switch (RSQ) operable at the end of the charging phase to transfer charge from the power supply to the first charge storage device (C1), before a subsequent discharging phase.

13. A drive circuit for an injector arrangement comprising a fuel injector, the drive circuit comprising a diagnostic tool (RF) in a connection of the drive circuit to a ground potential (VGND), the diagnostic tool (RF) being operable: a) to sense a detected current (Idect); andb) to provide a signal on detection of a fault, wherein the signal is provided when the detected current (Idect) is at variance from a threshold current (Itrip).

14. A drive circuit as claimed in claim 13, wherein the signal is provided when the detected current (Idect) is greater than the threshold current (Itrip).

15. A drive circuit as claimed in claim 13, wherein the connection of the drive circuit to the ground potential (VGND) is connected to a charge storage arrangement (C1, C2).

16. A drive circuit as claimed in claim 15, wherein the charge storage arrangement comprises: i) a first charge storage device (C1) for operative connection with the fuel injector during a charging phase so as to cause a charge current to flow therethrough; andii) a second charge storage device (C2) for operative connection with the fuel injector during a discharge phase so as to permit a discharge current to flow therethrough.

17. A drive circuit as claimed in claim 16, wherein the connection of the drive circuit to the ground potential (VGND) is connected to a switch arrangement (Q1, Q2) for operably controlling the connection of the fuel injector to the first charge storage device (C1) or the second charge storage device (C2).

18. A drive circuit as claimed in claim 17, wherein the switch arrangement comprises a charge switch (Q1) operable to close so as to activate the charging phase.

19. A drive circuit as claimed in claim 17, wherein the switch arrangement comprises a discharge switch (Q2) operable to close so as to activate the discharging phase.

20. A drive circuit as claimed in claim 19, wherein the connection of the drive circuit to the ground potential (VGND) is connected to the discharge switch (Q2).

21. A drive circuit as claimed in claim 16, further comprising a power supply and a regeneration switch (RSQ) operable at the end of the charging phase to transfer charge from the power supply to the first charge storage device (C1), before a subsequent discharging phase.

22. A drive circuit as claimed in claim 13, further comprising a selector switch (SQ1, SQ2) operable to select the fuel injector into the drive circuit and to deselect the fuel injector from the drive circuit.

23. A drive circuit for an injector arrangement comprising a fuel injector, the drive circuit comprising: i) a first charge storage device (C1) for operative connection with the fuel injector during a charging phase so as to cause a charge current to flow therethrough;ii) a second charge storage device (C2) for operative connection with the fuel injector during a discharge phase so as to permit a discharge current to flow therethrough; iii) a switch arrangement (Q1, Q2) for operably controlling the connection of the fuel injector to the first charge storage device (C1) or the second charge storage device (C2); andiv) a diagnostic tool (RH, RL; RF) operable to provide a signal on detection of a fault.

24. A drive circuit as claimed in claim 23, further comprising a selector switch arrangement (SQ1, SQ2) operable to select the fuel injector into the drive circuit and to deselect the fuel injector from the drive circuit.

25. A drive circuit as claimed in claim 24, wherein the diagnostic tool (RH, RL) is operable to: sense a measured voltage (VBIAS) between the injector and a known voltage level (VBAT, VGND) when the injector is deselected from the drive circuit; andprovide a short circuit fault signal on sensing of a measured voltage (VBIAS) that differs from a first predicted voltage (VPinjN, VBcalc).

26. A drive circuit as claimed in claim 24, wherein the diagnostic tool (RH, RL) is operable to: sense a measured voltage (VBIAS) between the injector and the known voltage level (VBAT, VGND) when the injector is selected in the drive circuit; andprovide an open circuit fault signal on sensing of a measured voltage (VBIAS) that differs from a second predicted voltage (VPinjN, VBcalc).

27. A drive circuit for an injector arrangement comprising a fuel injector, the drive circuit comprising: i) a first charge storage device (C1) for operative connection with the fuel injector during a charging phase so as to cause a charge current to flow therethrough;ii) a second charge storage device (C2) for operative connection with the fuel injector during a discharge phase so as to permit a discharge current to flow therethrough;iii) a switch arrangement (Q1, Q2) for operably controlling the connection of the fuel injector to the first charge storage device (C1) or the second charge storage device (C2);iv) a selector switch arrangement (SQ1, SQ2) operable to select the fuel injector into the drive circuit and to deselect the fuel injector from the drive circuit; andv) a diagnostic tool (RH, RL; RF) operable to: a) sense a measured voltage (VBIAS) between the injector and a known voltage level (VBAT, VGND) when the injector is deselected from the drive circuit; andb) provide a short circuit fault signal on sensing of a measured voltage (VBIAS) that differs from a first predicted voltage (VPinjN, VBcalc).

28. A drive circuit or an injector arrangement comprising a fuel injector, the drive circuit comprising: a selector switch arrangement (SQ1, SQ2) operable to select the fuel injector into the drive circuit and to deselect the fuel injector from the drive circuit; anda diagnostic tool (RH, RL) operable to: a) sense a measured voltage (VBIAS) between the injector and a known voltage level (VBAT, VGND) when the injector is deselected from the drive circuit; andb) provide a short circuit fault signal on sensing of a measured voltage (VBIAS) that differs from a first predicted voltage (VPinjN, VBcalc).

29. A drive circuit as claimed in claim 28, wherein the diagnostic tool (RH, RL) is further operable to: c) sense a measured voltage (VBIAS) between the injector and the known voltage level (VBAT, VGND) when the injector is selected in the drive circuit; andd) provide an open circuit fault signal on sensing of a measured voltage (VBIAS) that differs from a second predicted voltage (VPinjN, VBcalc).

30. An injector bank for an automotive engine, the injector bank comprising a fuel injector and a drive circuit as claimed in claim 28, wherein the fuel injector is operable by the drive circuit.

31. An engine control module for controlling the operation of an engine, the engine comprising a microprocessor for controlling the operation of the engine, a memory for recording data, and a drive circuit as claimed in claim 28, wherein the drive circuit is controllable by the microprocessor.

32. A method of detecting faults in a drive circuit for an injector arrangement comprising a fuel injector, the method comprising: a) sensing a measured voltage (VBIAS) between the injector and a known voltage level (VBAT, VGND), the measured voltage (VBIAS) being biased with respect to the known voltage (VBAT, VGND) to a predicted voltage (VPinjN, VBcalc) unless the drive circuit has a fault; andb) providing a fault signal on sensing of a measured voltage (VBIAS) that differs from the predicted voltage (VPinjN, VBcalc).

33. A method as claimed in claim 32, wherein the method further comprises operating selector a switch arrangement (SQ1, SQ2) to select the fuel injector into the drive circuit and to deselect the fuel injector from the drive circuit.

34. A method as claimed in claim 32, further comprising: i) sensing a detected current (Idect) through a connection of the drive circuit (20a) to the ground potential (VGND); andii) providing a signal when the detected current (Idect) is at variance from a threshold current (Itrip).

35. A method as claimed in claim 32, the injector arrangement comprising more than one fuel injector, wherein the method comprises selecting each fuel injector in turn.

36. A method of detecting faults in a drive circuit for an injector arrangement comprising a fuel injector, the method comprising: a) sensing a detected current (Idect) through a connection of the drive circuit(20a) to the ground potential (VGND); andb) providing a signal when the detected current (Idect) is at variance from a threshold current (Itrip).

37. A method as claimed in claim 36, comprising providing the signal when the detected current (Idect) is greater than the threshold current (Itrip).

38. A method as claimed in claim 36, the drive circuit further comprising a switch arrangement in which a charge switch (Q1) is operable to activate a charging phase, wherein the method further comprises operating the charge switch (Q1) prior to detection of a fault associated with the drive circuit.

39. A method as claimed in claim 36, the switch arrangement comprising a discharge switch (Q2) operable to activate the discharge phase, wherein the method further comprises operating the discharge switch (Q2) prior to detection of a fault associated with the drive circuit.

40. A method as claimed in claim 36, the drive circuit further comprising a power supply and a regeneration switch (RSQ) for operably transferring charge from the power supply to a first charge storage device (C1), wherein the method further comprises operating the regeneration switch (RSQ) prior to detection of a fault.

41. A method as claimed in claim 36, the drive circuit further comprising a selector switch arrangement (SQ1, SQ2) for selecting the fuel injector into the drive circuit and for deselecting the fuel injector from the drive circuit, the method further comprising operating the selector switch arrangement (SQ1, SQ2) prior to detection of a fault.

42. A method of detecting faults in a drive circuit for an injector arrangement comprising a fuel injector, the method comprising: a) sensing a measured voltage (VBIAS) between the injector and a known voltage level (VBAT, VGND) when the injector is deselected from the drive circuit; andb) providing a short circuit fault signal on sensing of a measured voltage (VBIAS) that differs from a first predicted voltage (VPinjN, VBcalc).

43. A method as claimed in claim 42, further comprising c) sensing a measured voltage (VBIAS) between the injector and the known voltage level (VBAT, VGND) when the injector is selected in the drive circuit; andd) providing an open circuit fault signal on sensing of a measured voltage (VBIAS) that differs from a second predicted voltage (VPinjN, VBcalc).

44. A computer program product comprising at least one computer program software portion which, when executed in an executing environment, is operable to implement one or more of the steps of the method as claimed in claim 42.

45. A data storage medium having the or each computer software portion of claim 44.

46. A microcomputer provided with a data storage medium as claimed in claim 45.