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Individual Print Head Coil Temperature Control System

IP.com Disclosure Number: IPCOM000041187D
Original Publication Date: 1987-Nov-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Zumbach, RG: AUTHOR

Abstract

The temperature of individual print head coils is monitored through a small sense resistor. If a threshold temperature has been reached, the print head is delayed until it is below the threshold temperature.

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Individual Print Head Coil Temperature Control System

The temperature of individual print head coils is monitored through a small sense resistor. If a threshold temperature has been reached, the print head is delayed until it is below the threshold temperature.

The temperature is monitored by placing a small sense resistor 1 in series with each print head coil 2 and print head driver 3. A reference voltage is generated across resistor 4, and the reference voltage is compared to the voltage across the sense resistor by comparator 5. Since the resistivity of the sense resistor varies as a function of the amount of current passing through the sense resistor, an increase in the temperature of the sense resistor corresponds to an increase in the temperature of the print head driver 3. The change of resistivity is linear and follows the relationship: R = R0 + T x 0.004RO, where RO is the resistivity at room temperature. Because the maximum allowable temperature rise is about 90 degree C, the maximum change in resistivity is about 8.1.

The voltage comparator determines when a maximum allowable temperature rise for each particular print head coil has occurred. The voltage comparator and sensing circuitry for each print head coil may be logically OR-ed together to provide a processor interrupt signal on line 6. This will stop the print head if any coil reaches the maximum allowable temperature and allow it to cool. By the use of the voltage comparator with the measurement...