Non-contact thermal temperature controller

Abstract

A temperature monitoring and control system interfaces with a host printing system through a communication medium to allow the host printing system to maintain control of heating lamps used to heat hot roll (fuser roll) to the required temperature. The temperature monitoring circuitry calibrates itself via the use of a black body calibration strip applied to the hot roller. The black body strip is used to determine the temperature and thus provide offset values for the hot roll cylinder, with respect to the thermal conductive coating. Temperature measurement according to the present invention utilizes infrared technology thermal sensors in conjunction with self-compensating controlling circuitry. The actual temperature of the coated surface is measured and compensated for by the use of Boolean algebraic logic as the hot roll cylinder is heated and during the course of the printing operation. This control device provides the advantage of a non-contact temperature controlling device, is that it offers a selection of specific temperatures in varying increments, which allows for different hot roll heating for different paper and other print media. This adjustment further allows for temperature adjustments to compensate for extremes and/or variations of moisture content of the print medium. Another advantage of the control device is that it adaptively controls based on the rotational speed of the hot roll.

What is claimed is:  
     
         1 . A temperature control device for use in controlling temperature of an electrophotographic hot roll, the device comprising: 
 plural non-contact sensors directed at different parts of the hot roll to generate sensor signals;    a differential amplifier that processes the generated sensor signals to produce a temperature indication signal;    a mapping circuit connected to the differential amplifier so as to perform a mapping function on the temperature indication signal to produce a mapped temperature signal;    a first comparison circuit connected to the mapping circuit so as to receive the mapped temperature signal and compare the mapped temperature signal to a predetermined temperature setting threshold, and produce a comparison result;    a speed determination circuit connected to receive a pulse signal indicative of the rotational speed of the hot roll so as to produce a hot roll speed status signal; and    a modulation circuit connected to receive the comparison result from the first comparison circuit and the hot roll speed status signal, causing heating of the hot roll to be modulated so as to maintain the temperature of the hot roll at a temperature corresponding to the predetermined temperature setting threshold.    
     
     
         2 . The temperature control device of    claim 1   , further comprising: 
 a display circuit connected to receive the temperature indication signal and provide a visual display of temperature of the hot roll.    
     
     
         3 . The temperature control device of    claim 1   , wherein the mapping circuit is a PROM circuit.  
     
     
         4 . The temperature control device of    claim 1   , wherein the mapping circuit is an EEPROM circuit.  
     
     
         5 . The temperature control device of    claim 1   , further comprising: 
 a second comparison circuit connected to the mapping circuit so as to receive the mapped temperature signal and compare the mapped temperature signal to a predetermined maximum temperature threshold, wherein the second comparison circuit initiates an alarm signal in the event that the mapped temperature signal exceeds the predetermined maximum temperature threshold.    
     
     
         6 . The temperature control device of    claim 1   , wherein one of the non-contact sensors is directed at a portion of the hot roll having a thermally conductive coating, and another of the non-contact sensors is directed to a black body strip on the hot roll.  
     
     
         7 . A temperature control device for use in controlling temperature of a heated element, the device comprising: 
 plural non-contact sensors directed at different parts of the heated element to generate sensor signals;    a differential amplifier that processes the generated sensor signals to produce a temperature indication signal;    a mapping circuit connected to the differential amplifier so as to perform a mapping function on the temperature indication signal to produce a mapped temperature signal;    a first comparison circuit connected to the mapping circuit so as to receive the mapped temperature signal and compare the mapped temperature signal to a predetermined temperature setting threshold, and produce a comparison result;    a speed determination circuit connected to receive a pulse signal indicative of the rotational speed of the heated element so as to produce a speed status signal; and    a modulation circuit connected to receive the comparison result from the first comparison circuit and the speed status signal, causing heating of the heated element to be modulated so as to maintain the temperature of the heated element at a temperature corresponding to the predetermined temperature setting threshold.    
     
     
         8 . The temperature control device of    claim 7   , further comprising: 
 a display circuit connected to receive the temperature indication signal and provide a visual display of temperature of the heated element.    
     
     
         9 . The temperature control device of    claim 7   , wherein the mapping circuit is a PROM circuit.  
     
     
         10 . The temperature control device of    claim 7   , wherein the mapping circuit is an EEPROM circuit.  
     
     
         11 . The temperature control device of    claim 7   , further comprising: 
 a second comparison circuit connected to the mapping circuit so as to receive the mapped temperature signal and compare the mapped temperature signal to a predetermined maximum temperature threshold, wherein the second comparison circuit initiates an alarm signal in the event that the mapped temperature signal exceeds the predetermined maximum temperature threshold.    
     
     
         12 . The temperature control device of    claim 7   , wherein one of the non-contact sensors is directed at a portion of the heated element having a thermally conductive coating, and another of the non-contact sensors is directed to a black body strip on the heated element.  
     
     
         13 . An electrophotographic printing device having a hot roller for fixing images on a recording medium, and having a control circuit for controlling temperature of the hot roller, the control circuit comprising: 
 plural non-contact sensors directed at different parts of the hot roll to generate sensor signals;    a differential amplifier that processes the generated sensor signals to produce a temperature indication signal;    a mapping circuit connected to the differential amplifier so as to perform a mapping function on the temperature indication signal to produce a mapped temperature signal;    a first comparison circuit connected to the mapping circuit so as to receive the mapped temperature signal and compare the mapped temperature signal to a predetermined temperature setting threshold, and produce a comparison result;    a speed determination circuit connected to receive a pulse signal indicative of the rotational speed of the hot roll so as to produce a hot roll speed status signal; and    a modulation circuit connected to receive the comparison result from the first comparison circuit and the hot roll speed status signal, causing heating of the hot roll to be modulated so as to maintain the temperature of the hot roll at a temperature corresponding to the predetermined temperature setting threshold.    
     
     
         14 . The electrophotographic printing device of    claim 13   , further comprising: 
 a display circuit connected to receive the temperature indication signal and provide a visual display of temperature of the hot roll.    
     
     
         15 . The electrophotographic printing device of    claim 13   , wherein the mapping circuit is a PROM circuit.  
     
     
         16 . The electrophotographic printing device of    claim 13   , wherein the mapping circuit is an EEPROM circuit.  
     
     
         17 . The electrophotographic printing device of    claim 13   , further comprising: 
 a second comparison circuit connected to the mapping circuit so as to receive the mapped temperature signal and compare the mapped temperature signal to a predetermined maximum temperature threshold, wherein the second comparison circuit initiates an alarm signal in the event that the mapped temperature signal exceeds the predetermined maximum temperature threshold.    
     
     
         18 . The electrophotographic printing device of    claim 13   , wherein one of the non-contact sensors is directed at a portion of the hot roll having a thermally conductive coating, and another of the non-contact sensors is directed to a black body strip on the hot roll.  
     
     
         19 . A temperature control device for use in controlling temperature of an electrophotographic hot roll, the device comprising: 
 plural non-contact sensors directed at different parts of the hot roll to generate sensor signals, wherein one of the non-contact sensors is directed at a portion of the hot roll having a thermally conductive coating, and another of the non-contact sensors is directed to a black body strip on the hot roll;    a differential amplifier that processes the generated sensor signals to produce a temperature indication signal;    a display circuit connected to receive the temperature indication signal and provide a visual display of temperature of the hot roll;    a PROM circuit connected to the differential amplifier so as to perform a mapping function on the temperature indication signal to produce a mapped temperature signal;    a first comparison circuit connected to the PROM circuit so as to receive the mapped temperature signal and compare the mapped temperature signal to a predetermined temperature setting threshold, and produce a comparison result;    a speed determination circuit connected to receive a pulse signal indicative of the rotational speed of the hot roll so as to produce a hot roll speed status signal;    a modulation circuit connected to receive the comparison result from the first comparison circuit and the hot roll speed status signal, causing heating of the hot roll to be modulated so as to maintain the temperature of the hot roll at a temperature corresponding to the predetermined temperature setting threshold; and    a second comparison circuit connected to the PROM circuit so as to receive the mapped temperature signal and compare the mapped temperature signal to a predetermined maximum temperature threshold, wherein the second comparison circuit initiates an alarm signal in the event that the mapped temperature signal exceeds the predetermined maximum temperature threshold.