Printhead nucleation detection using thermal response
View Patent ↗A method for determining the pulse width for driving printhead nozzles in a thermal inkjet printer. The printhead is preheated to a desired temperature during a maintenance mode. The printhead nozzle heaters are successively driven in respective heating intervals, where each successive heating interval is characterized by shorter drive pulse width pulses occurring at a higher pulse frequency. The printhead temperature data received during each heating interval is processed to determine a respective temperature slope. The temperature slopes are compared to a desired threshold temperature slope, and when a match is found, the pulse width associated with the matched temperature slope is used to drive the nozzle heaters during subsequent printer operations to print characters on a print medium.
1. A method of controlling a printer of the type having a printhead with a plurality of nozzles, a heater associated with each nozzle, and where the heater is responsive to a pulse for heating ink and jetting the ink through the nozzle, and a thermal sensor for measuring printhead temperature, comprising:
heating the printhead to a predetermined temperature;
driving the nozzle heaters during a first interval with pulses having a starting pulse width and a starting frequency;
driving the nozzle heaters during subsequent intervals with respective pulses having decremented pulse widths and frequencies having incremented frequencies;
processing a temperature change of the printhead during each interval to determine a main fire pulse width that caused a predetermined temperature change; and
using the main fire pulse width to drive the nozzle heaters to print characters on a print medium.
2. The method of claim 1 further including finding a temperature slope for each interval, and comparing the temperature slopes with a predetermined threshold temperature slope to determine the main fire pulse width.
3. The method of claim 2 further including finding a temperature slope between a jetting region and a transition region of the printhead.
4. The method of claim 2 further including finding a temperature slope at an ink nucleation cutoff state of the printhead.
5. The method of claim 1 further including driving the printhead heaters during each interval with pulse width and frequency intervals having a substantially constant power.
6. The method of claim 1 further including defining the pulse widths and the associated frequencies for each heating interval to produce a printhead temperature change in a region between a jetting region and a transition region of the printhead.
7. The method of claim 1 further including finding the main fire pulse width for each different printhead installed in the printer.
8. The method of claim 1 further including obtaining a plurality of printhead temperature samples during each interval to find a temperature slope of the printhead during the respective interval.
9. The method of claim 1 further including preheating the printhead to the predetermined temperature so that ink nucleation occurs in the printhead nozzles.
10. The method of claim 1 further including jetting the same number of nozzles during each interval.
11. A method of controlling a printer of the type having a printhead with a plurality of nozzles, a heater associated with each nozzle, and where the heater is responsive to a pulse for heating ink and jetting the ink through the nozzle, and a thermal sensor for measuring printhead temperature, comprising:
preheating the printhead to a predetermined temperature;
successively driving the heater with a heating interval, where each successive heating interval is characterized by shorter pulse width pulses at a higher pulse frequency;
processing printhead temperature data received during each heating interval to identify a desired criterion;
when the desired criterion is found, associating the desired criterion with a heating interval in which ink nucleation begins to cease and a main fire pulse width used in the heating interval in which ink nucleation began to cease; and
driving the heater with the main fire pulse width during subsequent printer operations to print characters on a print medium.
12. The method of claim 11 further including obtaining a plurality of printhead temperature samples from the thermal sensor during each said heating interval.
13. The method of claim 11 further including obtaining a plurality of printhead temperature samples from a plurality of thermal sensors during each said heating interval.
14. The method of claim 13 , further including finding a temperature slope of the printhead temperature of each of the thermal sensors, and finding a mean of the temperature slopes and storing the mean temperature slope for each heating interval.
15. The method of claim 14 further including receiving a printhead temperature from each of a thermal sensor associated with nozzles jetting a different color ink.
16. The method of claim 11 further including selecting the desired criterion as nucleation cutoff.
17. A printer of the type having a printhead with a plurality of nozzles, a heater associated with each nozzle, and where the heater is responsive to a pulse for heating ink and jetting the ink through the nozzle, and a thermal sensor for measuring printhead temperature, comprising:
a controller programmed to:
successively drive the heater during a heating interval where each successive heating interval is characterized by shorter pulse width pulses at a higher pulse frequency;
process printhead temperature data received during each heating interval to identify a desired criterion;
associate the desired criterion with a heating interval and a main fire pulse width used in the heating interval; and
drive the heater with the main fire pulse width during subsequent printer operations to print characters on a print medium.
18. The printer of claim 17 , wherein said desired criterion comprises a nucleation cutoff.