Thermal recording method using drive signal pulse widths changed at time intervals within thermal head temperature measuring time intervals

• US 5,208,607 A
• Filed: 08/30/1991
• Issued: 05/04/1993
• Est. Priority Date: 09/03/1990
• Status: Expired due to Fees

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Tokumasu, Takahiko, Ohashi, Takeo
• Primary Examiner(s): Fuller, Benjamin R.
• Assistant Examiner(s): Le, N.
• Application Number:
  US07/753,074
• Time in Patent Office: 613 Days
• Field of Search: 346/76 PH, 346/ 1.1, 400/120
• US Class Current: 347/179
• CPC Class Codes: B41J 2/365 by compensation for variation in temperature

Abstract

A heat-sensitive recording method of performing a thermal printing at variable printing time intervals by a thermal head in a facsimile apparatus. The method includes the steps of determining a pulse width corresponding to a thermal head temperature, from a measured resistance of a thermistor measured at a first time interval, on the basis of a relationship between thermal head temperature and pulse width, storing the determined pulse width corresponding to the temperature in a first memory area and storing a recording power pulse width corresponding to the pulse width in a second memory area, and correcting the recording power pulse width on the basis of a relationship between thermistor resistance and thermal head temperature by changing the recording power pulse width at a second time interval by comparing the same with the pulse width, so that a thermal printing is performed in which the recording power pulse width is varied in gradual steps by applying a printing power pulse with the thus corrected pulse width to the thermal head.

Claims

1. A heat-sensitive thermal recording method of performing a thermal printing at variable printing time intervals by a heat-generating part in a facsimile system having a memory part in which a pulse width table defining a relationship between heat-generating part temperature and measurement pulse width is stored, said heat-sensitive thermal recording method comprising steps of:

measuring a temperature of the heat-generating part from a resistance of thermistor provided within the heat-generating part, said resistance of said thermistor being measured at a first time interval;

determining a measurement pulse width corresponding to said heat-generating part temperature in accordance with said pulse width table stored in said memory part;

storing said measurement pulse width corresponding to said temperature in a first memory area;

periodically determining a recording power pulse width and storing the recording power pulse width in a second memory area;

detecting whether the recording power pulse width stored in the second memory area is smaller than the measurement pulse width stored in the first memory area; and

correcting said recording power pulse width stored in said second memory area into a new recording power pulse width at a second time interval, said new recording power pulse width being generated by one of (a) adding a predetermined value to the recording power pulse width stored in said second memory area when said recording power pulse width is smaller than said measurement pulse width; and

(b) subtracting the predetermined value from said recording power pulse width when it is greater than said measurement pulse width;

so that a thermal printing is performed in which the recording power pulse width is varied in gradual steps by applying a printing power pulse with the thus corrected pulse width to the heat-generating part;

wherein said predetermined value is set from the heat-generating part temperature in accordance with a relationship between thermistor resistance and heat-generating part temperature;

wherein said first time interval at which said resistance of said thermistor is measured is divided into small time intervals each of which is equal to said second time interval at which said recording power pulse width stored in the second memory area is corrected.

2. The method as claimed in claim 1, wherein said first time interval is equal to 160 milliseconds and said second time interval is equal to 40 milliseconds.

3. The method as claimed in claim 1, wherein said facsimile system includes said memory part in which said pulse width table is stored, and a second memory part having said first and second memory areas, said measurement pulse width being stored in said first memory area and said recording power pulse width being stored in said second memory area.

4. The method as claimed in claim 1, wherein heat-generating part temperature values included in said pulse width table stored in said memory part are defined such that said temperature values in a predetermined temperature range are varied in equal steps with respect to changes in measurement pulse width values.