Thermal monitoring system for determining nozzle health

• US 6,460,964 B2
• Filed: 11/29/2000
• Issued: 10/08/2002
• Est. Priority Date: 11/29/2000
• Status: Expired due to Fees

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Osborne, William S.
• Primary Examiner(s): HALLACHER, CRAIG ALAN
• Application Number:
  US09/726,963
• Publication Number:
  US 20020063745A1
• Time in Patent Office: 678 Days
• Field of Search: 347/19, 347/7, 347/40, 347/17, 347/23
• US Class Current: 347/19
• CPC Class Codes: B41J 2/125 Sensors, e.g. deflection sensors nozzle clogging detection for cleaning reasons B41J2/16579; detection for compensation for failed nozzles B41J2/2139
• CPC Class Codes: B41J 2/16579 Detection means therefor, e.g. for nozzle clogging

Abstract

A thermal monitoring system determines whether a fluid ejecting nozzle is healthy and operating in a thermal fluid ejection system to eject precise amounts of fluid in response to a firing signal. If not, a nozzle recovery routine is preformed to remove any nozzle blockages, with different routines being preformed to address the type of blockage encountered. If recovery is not possible, or if the nozzle failure is detected “on-the-fly” during a normal fluid application routine, a substitute healthy nozzle is engaged without interrupting the job. Nozzle health is determined by monitoring the temperature change of the nozzle following application of the firing signal. In one embodiment, an inkjet printing mechanism uses a thermal inkjet printhead to eject an inkjet ink as the fluid. A method of monitoring the health of a fluid ejection nozzle is also provided.

Claims

1. A method of monitoring the health of a fluid ejection nozzle which normally ejects a fluid in response to a firing signal, comprising:

applying a firing signal to said nozzle;

thereafter, monitoring the temperature change of the nozzle;

determining from the monitored temperature change whether the nozzle ejected said fluid in response to the application of the firing signal; and

when said nozzle fails to eject said fluid, ejecting fluid from a substitute nozzle.

2. A method according to claim 1 wherein the firing signal is applied during a normal fluid ejection job.

3. A method according to claim 2 wherein following completion of said normal fluid ejection job, the method further includes recovering the functionality of said nozzle which failed to eject said fluid.

4. A method according to claim 3 wherein the method further includes determining whether said recovering of the nozzle which failed was successful.

5. A method according to claim 4 wherein when said recovering of the nozzle which failed was unsuccessful, the method further includes continuing to use said substitute nozzle as a substitute for the nozzle which failed.

6. A method according to claim 5 wherein said fluid comprises an inkjet ink, and said normal fluid ejection job comprises a print job.

7. A method according to claim 1 wherein when the firing signal is applied during a normal nozzle spitting routine and said nozzle failed to eject said fluid, the method further includes recovering the functionality of said failed nozzle.

8. A method according to claim 7 wherein the method further includes deciding what type of blockage caused the failure of said nozzle, and said recovering comprises using a recovery routine corresponding to the decided type of blockage which caused the failure of said nozzle.

9. A method according to claim 8 wherein:

when the decided type of blockage comprises a solid blockage, said recovery routine comprises wiping said nozzle; and

when the decided type of blockage comprises a vapor blockage, said recovery routine comprises applying pressure to remove said vapor blockage from said nozzle.

10. A method according to claim 8 wherein the method further includes determining whether said recovering of said failed nozzle was successful.

11. A method according to claim 10 wherein when said recovering of said failed nozzle was unsuccessful, the method further includes continuing to use said substitute nozzle as a substitute for sailed failed nozzle.

12. A method according to claim 8 wherein said fluid comprises an inkjet ink.

13. A method according to claim 1 wherein:

said applying comprises applying said firing signal to a firing resistor associated with said nozzle; and

said monitoring comprises monitoring the change in resistivity of said firing resistor.

14. A method according to claim 1 wherein:

said applying comprises applying said firing signal to a firing resistor associated with said nozzle; and

said monitoring comprises monitoring the change in conductivity of said firing resistor.

15. A method according to claim 1 wherein:

the method further comprises providing a thermal sensor thermally adjacent to said nozzle to generate a temperature signal in response to temperature changes of said nozzle; and

said monitoring comprises monitoring the temperature signal.

16. A method according to claim 15 wherein said thermal sensor comprises a heat sensing resistor.

17. A method according to claim 1 wherein said determining comprises:

graphing a trace of the monitored temperature change over time; and

when an inflection region is found in said trace, determining said nozzle successfully ejected said fluid.

18. A method according to claim 1 wherein said determining comprises:

applying a curve fitting routine to the monitored temperature change over time and generating a trace therefrom; and

when an inflection point is found in said trace, determining said nozzle successfully ejected said fluid.

19. A method according to claim 1 wherein said determining comprises:

generating a second derivative curve of the monitored temperature change over time; and

when the second derivative curve passes through zero, determining said nozzle successfully ejected said fluid.

20. A method according to claim 1 wherein said determining comprises analyzing the rate of rise of the monitored temperature change following application of the firing signal.

21. A method according to claim 20 wherein when the analyzed rate of rise is greater than the rate of rise for a normally function nozzle, determining said nozzle is blocked by a vapor bubble.

22. A method according to claim 21 wherein when said nozzle is blocked by said vapor bubble, the method further includes recovering said nozzle by applying pressure to remove said vapor bubble from said nozzle.

23. A method of monitoring the health of a fluid ejection nozzle which normally ejects a fluid in response to a firing signal, comprising:

applying a firing signal to said nozzle;

thereafter, monitoring the temperature change of the nozzle;

determining from the monitored temperature change whether the nozzle ejected said fluid in response to the application of the firing signal;

when said nozzle fails to eject said fluid, deciding which type of blockage caused the failure of said nozzle; and

recovering functionality of said nozzle, including using a recovery routine corresponding to the decided type of blockage.

24. A method according to claim 23 wherein when the decided type of blockage comprises a solid blockage, said recovery routine comprises wiping said nozzle.

25. A method according to claim 24 wherein said recovery routine further comprises applying a solvent to said nozzle.

26. A method according to claim 23 wherein when the decided type of blockage comprises a vapor blockage, said recovery routine comprises applying a positive pressure to push said vapor blockage out of said nozzle.

27. A method according to claim 23 wherein when the decided type of blockage comprises a vapor blockage, said recovery routine comprises applying a vacuum pressure to pull said vapor blockage out of said nozzle.

28. A method according to claim 23 wherein said fluid comprises an inkjet ink.

29. A method according to claim 23 wherein the method further includes determining whether said recovering of said failed nozzle was successful.

30. A method according to claim 29 wherein when said recovering of said failed nozzle was unsuccessful, the method further includes using another nozzle as a substitute for said failed nozzle.

32. A fluid ejection mechanism according to claim 30 wherein when the controller determines said nozzle has failed during a normal fluid ejection job, the controller diverts said firing signal to said another nozzle without interrupting said normal fluid ejection job.

31. A fluid ejection mechanism, comprising:

a fluid reservoir containing a fluid;

a fluid jetting head having a nozzle in fluid communication with said reservoir to receive said fluid and normally, in response to a firing signal, eject said fluid therethrough;

a temperature sensor which monitors temperature change of said nozzle and generates a temperature signal in response thereto; and

a controller which generates said firing signal, and which determines from the temperature signal whether the nozzle ejected said fluid in response to the application of the firing signal,

wherein the jetting head has another nozzle in fluid communication with said reservoir, and when the controller determines said nozzle has failed to eject said fluid, the controller diverts said firing signal to said another nozzle to eject said fluid therethrough as a substitute nozzle for said failed nozzle.

33. A fluid ejection mechanism according to claim 31 wherein:

the fluid ejection mechanism comprises an inkjet printing mechanism;

the fluid comprises an inkjet ink; and

the fluid jetting head comprises an inkjet printhead.

34. A fluid ejection mechanism according to claim 31 wherein the fluid jetting head has a firing resistor associated with said nozzle, with the firing resistor operating in response to said firing signal.

35. A fluid ejection mechanism according to claim 31 wherein the temperature sensor comprises a firing resistor associated with said nozzle, with the firing resistor having a resistivity which changes in response to temperature changes of said nozzle, with the temperature signal comprising a signal representative of the firing resistor resistivity.

36. A fluid ejection mechanism according to claim 31 wherein the temperature sensor comprises a firing resistor associated with said nozzle, with the firing resistor having a conductivity which changes in response to temperature changes of said nozzle, with the temperature signal comprising a signal representative of the firing resistor conductivity.

37. A fluid ejection mechanism according to claim 31 wherein the temperature sensor comprises a heat sensing resistor thermally adjacent to said nozzle to generate said temperature signal.

38. A fluid ejection mechanism according to claim 31 wherein the controller analyzes the temperature signal by generating a graph of the monitored temperature change over time, and when an inflection region is found in the graph the controller determines said nozzle successfully ejected said fluid.

39. A fluid ejection mechanism according to claim 31 wherein the controller analyzes the temperature signal by applying a curve fitting routine to the monitored temperature change over time and generating a graph therefrom, and when an inflection point is found in the graph the controller determines said nozzle successfully ejected said fluid.

40. A fluid ejection mechanism according to claim 31 wherein the controller analyzes the temperature signal by generating a second derivative curve of the monitored temperature change over time, and when the second derivative curve passes through zero the controller determines said nozzle successfully ejected said fluid.

41. A fluid ejection mechanism according to claim 31 wherein the controller analyzes the temperature signal by analyzing the rate of rise of the monitored temperature change following generation of the firing signal.

42. A fluid ejection mechanism, comprising:

a fluid reservoir containing a fluid;

a fluid jetting head having a nozzle in fluid communication with said reservoir to receive said fluid and normally, in response to a firing signal, eject said fluid therethrough;

a temperature sensor which monitors temperature change of said nozzle and generates a temperature signal in response thereto; and

a controller which generates said firing signal, and which determines from the temperature signal whether the nozzle ejected said fluid in response to the application of the firing signal,

wherein when the controller determines said nozzle has failed to eject said fluid due to a nozzle blockage, the controller determines the type of nozzle blockage and generates a recovery signal to remove the determined type of nozzle blockage.

43. A fluid ejection mechanism according to claim 42 wherein the controller analyzes the temperature signal to determine the type of nozzle blockage.

44. A fluid ejection mechanism according to claim 43 wherein:

the mechanism further includes a priming mechanism which applies a vacuum to the nozzle in response to a priming signal; and

when the controller determines the type of nozzle blockage comprises a vapor blockage, the recovery signal generated comprises the priming signal.

45. A fluid ejection mechanism according to claim 43 wherein:

the mechanism further includes a positive pressure mechanism which applies a positive pressure to the fluid within said reservoir in response to a pressure signal; and

when the controller determines the type of nozzle blockage comprises a vapor blockage, the recovery signal generated comprises the pressure signal.

46. A fluid ejection mechanism according to claim 43 wherein:

the mechanism further includes a wiping mechanism which wipes the nozzle in response to a wiping signal; and

when the controller determines the type of nozzle blockage comprises a solid blockage, the recovery signal generated comprises the wiping signal.

47. A fluid ejection mechanism according to claim 46 wherein:

the mechanism further includes a solvent application mechanism which applies a solvent for said fluid to the nozzle in response to a solvent application signal; and

when the controller determines the type of nozzle blockage comprises a solid blockage, the recovery signal generated comprises the solvent application signal.

48. A fluid ejection mechanism, comprising:

a fluid reservoir containing a fluid;

a fluid jetting head having a nozzle in fluid communication with said reservoir to receive said fluid and normally, in response to a firing signal, eject said fluid therethrough;

means for applying the firing signal to said nozzle;

means for monitoring the temperature change of the nozzle;

means for determining from the monitored temperature change whether the nozzle ejected said fluid in response to the application of the firing signal; and

means for ejecting fluid from a substitute nozzle when said nozzle fails to eject said fluid.

49. A fluid ejection mechanism according to claim 48 further including:

responsive to a first recovery signal, first means for recovering said nozzle when failing to eject said fluid due to a first type of block a

responsive to a second recovery signal, second means for recovering said nozzle. when failing to eject said fluid due to a second type of blockage;

means for determining whether the first type of blockage or the second type of blockage has occurred; and

means for generating the first recovery signal when the first type of blockage is determined to have occurred, and for generating the second recovery signal when the second type of blockage is determined to have occurred.

50. A fluid ejection mechanism according to claim 48 wherein:

the fluid ejection mechanism comprises an inkjet printing mechanism;

the fluid comprises an inkjet ink; and

the fluid jetting head comprises an inkjet printhead.

51. A fluid ejection mechanism, comprising:

a fluid reservoir containing a fluid;

a fluid jetting head having a nozzle in fluid communication with said reservoir to receive said fluid and normally, in response to a firing signal, eject said fluid therethrough;

means for applying the firing signal to said nozzle;

means for monitoring the temperature change of the nozzle;

means for determining from the monitored temperature change whether the nozzle. ejected said fluid in response to the application of the firing signal; and

means for determining when said nozzle has failed to eject said fluid due to a nozzle blockage and generating a recovery signal to remove the determined type of nozzle blockage.

52. A fluid ejection mechanism according to claim 51 further including:

means for ejecting fluid from a substitute nozzle when said nozzle fails to eject said fluid.

53. A fluid ejection mechanism according to claim 51 wherein:

the fluid ejection mechanism comprises an inkjet printing mechanism;

the fluid comprises an inkjet ink; and

the fluid jetting head comprises an inkjet printhead.