Electrophotography – Control of electrophotography process – Control of fixing
Reexamination Certificate
1999-11-09
2001-02-13
Beatty, Robert (Department: 2852)
Electrophotography
Control of electrophotography process
Control of fixing
C399S069000, C219S216000
Reexamination Certificate
active
06188854
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to electrophotographic image forming equipment. More particularly, the present invention relates to a method of controlling the temperature of a cylinder used in the printing process for fixing a toner image.
2. Background Information
In most electrophotographic printing applications, the need exists for precision temperature control for maintaining adequate fusing roll temperature for the fusing of toner to a medium which is typically paper.
In most situations, the hot roller (or “fusing roll”) is heated to a particular temperature at which it allows fusing of a toner to a medium. This temperature must be precisely controlled since, if the roller is too hot, the medium can be burned, or if the temperature is too cool, the toner will not adhere to the medium resulting in the image or words being smeared on the paper. Further, the temperature at which the hot roller must be kept varies with both the media on which information is printed and the characteristics of the toner. Typically, temperature is determined by a contact thermometer or thermocouple of some type in direct contact with the hot roll.
Current methods for controlling the temperature of a heated cylinder or roll are through the use of a ferrite chip that is charged with a magnetic field. The magnetic flux is then measured through a sensor, resulting in the generation of a pulse used to determine the cylinder's temperature. The ferrite chip fails to accept magnetic charge value when the optimum temperature is achieved, thus signaling the electronics of the printer that the required temperature has been reached since a pulse was not generated.
Another method of measuring cylinder temperature is through the use of contact thermal sensors and thermal fuses. These contact sensors measure the temperature of the heated roller through a heat transfer process dictated by positive contact with the surface of the hot roller.
What is needed is a non-contact temperature controlling device that can determine the ambient air temperature of a printer fixing or fusing device, measure the reflectance of a heated roller, and measure the temperature of a thermal coating applied to the heated roller used in the fixing of toner on a printed media. What is also needed is a non-contact temperature controlling device that is adjustable based upon media and toner characteristics and that is amenable to use by a layman operator of the printing system without special equipment or other specialized knowledge.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide for non-contact temperature control of fusing rollers in the electrophotographic process.
It is another object of the present invention to provide a non-contact temperature controlling device that can determine the ambient air temperature of a printer fixing or fusing device, measure the reflectance of a heated cylindrical roller, and measure the temperature of a thermal coating applied to a cylinder used in the fixing of toner on a printed media.
It is a further object of the present invention to provide for specific temperature adjustments to account for variations in moisture content of the print media being used.
It is yet another object of the present invention to provide for specific temperature adjustments to account for variations in characteristics of the toner and the print media being used.
The present invention is a device used for controlling the temperature of a hot roll cylinder used in the printing process. During the process of heating a cylinder for the purpose of fixing a toner image in an electrophotographic printing system (termed a hot roller, hot roll, or fusing roll), the print media which is in contact with the heated roll removes some of the applied heat, thus causing the hot roll to cool and thereby degrade the performance of the hot roll. It is therefore critical that the hot roll maintain its required temperature in order for subsequent prints to have the toner appropriately fused to the print media. The present invention not only monitors the temperature of the hot roller but corrects the operating temperature to within a prescribed parameter associated with the print media being used.
A temperature monitoring and control subsystem according to the present invention interfaces with the host printing system through a communication medium to allow the host printing system to maintain control of the heating lamps used to heat the hot roll to the required temperature based upon input from the present invention.
The temperature monitoring circuitry according to the present invention calibrates itself via the use of a black body calibration strip applied to the hot roller. This black body strip is used to determine the temperature and thus provide offset values for the hot roll cylinder to the thermal conductive coating. The black body calibration surface comprises a non-expansive material capable of tolerating the maximum heat applied to the hot roll cylinder without losing its non-reflectance (emissive) properties.
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.
An advantage of such a controlling device, that is, 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.
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Coleman Tommy C.
Lauver Rico
Beatty Robert
Roberts Abokhair & Mardula LLC
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