Patent
Thermal printer and method of controlling a thermal print head
| العنوان: | Thermal printer and method of controlling a thermal print head |
|---|---|
| Patent Number: | 5,365,257 |
| تاريخ النشر: | November 15, 1994 |
| Appl. No: | 08/095,880 |
| Application Filed: | July 22, 1993 |
| مستخلص: | A thermal printer drive control apparatus of the type having a thermal print head comprising a plurality of heating elements provides for reliable cost effective thermal head temperature detection by means of producing multiple, different current flow intervals that are applied to binary data to produce data drive signals for the heating elements. The current flow intervals are based upon historical drive data derived from linear temperature conditions sensed at the thermal print head. This information is converted to a digitized representation for use in conjunction with a table placed in memory that provides predetermined current flow intervals based upon the digitized representation. Further, circuitry is provided to produce heating element drive signals having pulse widths based upon the determined current flow intervals. |
| Inventors: | Minowa, Masahiro (Suwa, JPX); Kobayashi, Naoki (Suwa, JPX); Nakajima, Satoshi (Suwa, JPX); Furuhata, Tadashi (Suwa, JPX) |
| Assignees: | Seiko Epson Corporation (Tokyo, JPX) |
| Claim: | What is claimed is |
| Claim: | 1. A method of controlling a thermal print head in a thermal printer having a plurality of heating elements, a sensor mounted on the print head, comprising the steps of |
| Claim: | detecting an ambient temperature of the print head using said sensor when power is first applied to the printer or when a predetermined amount of time has elapsed since a last printing operation |
| Claim: | detecting a print head operating temperature of the print head using said sensor during printing operation |
| Claim: | determining an energy value based on both the detected ambient head temperature and the detected thermal head temperature, and |
| Claim: | driving the heat elements in the print head based on the determined energy value. |
| Claim: | 2. The method of claim 1 wherein the steps of detecting is accomplished employing an A/D converter. |
| Claim: | 3. The method of claim 1 further comprising the steps of |
| Claim: | determining a standard value based on a previously detected ambient temperature |
| Claim: | periodically detecting print head operating temperature during printing operation for determining a current correction value based on a change in print head temperature relative to the previously detected ambient temperature |
| Claim: | periodically calculating an energy value based on both the current correction value and the standard value, and |
| Claim: | applying the calculated energy value in driving the heating elements of the thermal print head. |
| Claim: | 4. The method of claim 3 further comprising the steps of |
| Claim: | periodically updating the ambient temperature on occasions when a predetermined amount of time has elapsed since a last printing operation of the printer, and |
| Claim: | calculating a new standard value based upon the updated ambient temperature, and |
| Claim: | utilizing the new standard value with a periodically updated current condition value for calculating a new energy value until the ambient temperature is again updated to provide a new standard value. |
| Claim: | 5. The method of claim 3 wherein the calculated energy value is a determined pulse width of electrical energy to be applied to the thermal print elements. |
| Claim: | 6. A thermal printer comprising |
| Claim: | a thermal print head having a plurality of heating elements formed relative to a print head baseplate |
| Claim: | a sensor in said baseplate for providing a value corresponding to the instantaneous print head temperature |
| Claim: | head temperature detection means connected to said sensor for determining a temperature value based upon said corresponding value produced at said sensor |
| Claim: | timing means for providing a temperature detect signal when operation of said print head has been inactive for a determined period of time |
| Claim: | said head temperature detection means for detecting, via said sensor, (a) an ambient temperature of said print head when power is first applied to the printer or upon receipt of said temperature detect signal and (b) a thermal head operating temperature during printing operation of said heating elements |
| Claim: | controller means connected to said heating elements for applying energy signals to operate said heating elements |
| Claim: | energy control means connected to said temperature detection means and said controller means for providing an energy value determinative of a relative magnitude for said energy signals provided by said controller means based upon both said detected ambient temperature value and said detected operating temperature value determined by said head temperature detection means via said sensor. |
| Claim: | 7. The printer of claim 6 where in said energy signal magnitudes comprise pulse widths of current flow intervals used to apply current to said printing elements. |
| Claim: | 8. The printer of claim 6 wherein said head temperature detection means comprises a A/D converter for generating a digital value representative of said detected ambient and operating temperature values. |
| Claim: | 9. The printer of claim 6 further comprising |
| Claim: | mode selection means for selecting prescribed printing parameters based upon printer type |
| Claim: | storage means for receiving and storing present print data and at least one previous print data |
| Claim: | gate means in said controller means and coupled to said storage means for activating energizing signals with respect to each of said heating elements, said activating energizing signals divided into a primary energizing interval determined according to present driving data and secondary energizing intervals determined according to previous print data |
| Claim: | said energy control means connected to said gate means and mode selection means for calculating a corrected pulse width coefficient based upon a standard pulse width value and current print head operating temperature and for determining the primary and secondary energizing intervals based on said standard pulse width as correlated to said correlated pulse width coefficient and said selected printing parameters. |
| Claim: | 10. The printer of claim 9 wherein said controller means continually revises said energizing signals based upon both said detected ambient and detected current thermal head operating temperature values. |
| Claim: | 11. The printer of claim 6 further comprising |
| Claim: | memory storage means for storing energy value correction coefficients; and |
| Claim: | said energy control means further comprises means for generating a functional relationship between a determination of a revised energy magnitude based upon detected current operating temperature values and stored energy value correction coefficients, said revised energy magnitude being calculated using said relationship. |
| Claim: | 12. The printer of claim 11 wherein said relationship is substantially linear. |
| Claim: | 13. The printer of claim 11 wherein said relationship is substantially nonlinear. |
| Claim: | 14. The printer of claim 11 wherein said relationship is substantially quadratic. |
| Claim: | 15. The printer of claim 6 further including means in said energy control means for continually revising said energy value based upon a substantially linear relationship between a revised value of said energy value based on current thermal head operating temperature value as modified by particular thermal printer characteristics. |
| Claim: | 16. The printer of claim 6 wherein said energy control means further comprises |
| Claim: | print density detection means for providing a value representative of a current print density produced at said thermal print head, and |
| Claim: | means in said energy control means for continually revising said energy value based upon a substantially linear relationship between a revised value of said energy value based on current thermal head operating temperature value and the detected print density at said print head. |
| Claim: | 17. The printer of claim 6 wherein said energy control means further comprises |
| Claim: | means for revising said energy values based upon said detected ambient and current operating temperature values of said print head, detected print density at said print head, and printing mode characteristics of said thermal printer. |
| Claim: | 18. The printer of claim 17 where in said energy signal magnitudes comprise pulse widths of current flow intervals used to apply current to said printing elements. |
| Claim: | 19. The printer of claim 6 wherein said energy control means wherein said temperature detection means periodically detects and updates said ambient temperature at said thermal print head been idle for a predetermined period of time via said timing means; and |
| Claim: | circuit means for revising said energy value based upon said updated ambient temperature value and said current thermal head operating temperature value. |
| Claim: | 20. The printer of claim 19 wherein said revised energy value is further based upon detected print density at said print head, and printing mode characteristics of said thermal printer. |
| Claim: | 21. The printer of claim 19 wherein said energy signal magnitudes comprise pulse widths of current flow intervals used to apply current to said printing elements. |
| Current U.S. Class: | 346/76PH; 347/17; 347/61 |
| Current International Class: | B41J 2375; B41J 236 |
| Patent References Cited: | 4590484 May 1986 Matsushita 4845514 July 1989 Mitsushima et al. 4912485 March 1990 Minowa 4983054 January 1991 Nishiura 5255011 October 1993 Minowa et al. |
| Primary Examiner: | Fuller, Benjamin R. |
| Assistant Examiner: | Tran, Huan |
| Attorney, Agent or Firm: | Carothers, Jr., W. Douglas |
| رقم الانضمام: | edspgr.05365257 |
| قاعدة البيانات: | USPTO Patent Grants |
| الوصف غير متاح. |