JPH0876635A - Temp. controlling method for fixing roll - Google Patents

Abstract

PURPOSE: To prolong the service life of a fixing roll, to prevent a hot offsetting and to increase the reliability of the electrophotographic device by maintaining the temp. of the fixing roll in the vicinity of the fixing temp. with respect to temp. controlling method for the fixing roll adopted to the fixing device of the electrophotographic device. CONSTITUTION: In the fixing device provided with a fixing roll 1, heater lamps 6 and 7 disposed inside the fixing roll 1, low temp. thermometer element 3 and a high temp. thermometer element 4 attached on the same periphery of the fixing roll 1, and a sensor head 5 disposed in a non-contact state opposite to the the thermometer elements 3 and 4 for taking out the signal change of the thermometer elements 3 and 4, the set temp. of the high temp. thermometer element 4 is set at the fixing temp. of the fixing roll l and the set temp. of the low temp. thermometer element 3 is set lower than the high temp. element 4, and moreover the respective heater lamp 6 and 7 is independently operated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for an electrophotographic apparatus such as an electrophotographic copying machine and a printer, and more particularly to a temperature control method for a fixing roll.

[0002]

2. Description of the Related Art In an image forming process of an electrophotographic apparatus, that is, a printing process, as one of methods for heating and fixing a toner image electrostatically transferred onto a surface of a printing paper, a method for fixing a toner image between a fixing roll and a pressure roll A heating / pressurizing method of passing a sheet is known, and has been conventionally used in a copying machine, a printer, or the like.

The structure of the fixing roll and the temperature control method in the prior art will be described below. A release layer made of a fluororesin is formed on the surface of the fixing roll, and two heater lamps A and B are provided inside. The heater lamp A has a heat generation area having the same length as the maximum print paper width, and the heater lamp B has a heat generation area shorter than the print paper width in the central portion of the print paper where the temperature drops greatly during printing. On the same circumference of the surface of the fixing roll, a low temperature detecting element having a fixing temperature of the fixing roll as a setting temperature, a high temperature detecting element having a higher temperature as a setting temperature, and a non-contact type facing the temperature detecting element. A sensor head that is provided in the sensor and takes out a signal change of the temperature detecting element is provided. The temperature detecting element emits a signal (magnetism) at a temperature lower than the set temperature and does not emit a signal at a temperature higher than the set temperature. The fixing temperature of the fixing roll is usually 200 ° C,
The set temperature A of the low temperature detection element is set to 200 ° C, and the set temperature B of the high temperature detection element is set to 300 ° C, which is 100 ° C higher than the set temperature A.

FIG. 5 shows a temperature control method for the fixing roll having the above structure. In both the non-printing state and the printing state of the electrophotographic apparatus, when the temperature of the fixing roll is equal to or lower than the set temperature A, the low temperature detecting element and the high temperature detecting element emit a signal. At this time, the sensor head takes out a signal from one of the temperature measuring elements and then takes out a signal from the other temperature measuring element during one rotation time T of the fixing roll. The above signal is input to the heater lamp control device connected to the sensor head to cause the heater lamps A and B to generate heat at the same time. As a result, the temperature of the fixing roll rises, and when it becomes higher than the set temperature A, the low temperature detecting element does not emit a signal. At this time, the sensor head does not take out any signal during the time T after taking out one signal. The heater lamp control device judges this and stops the heat generation of the heater lamps A and B at the same time. This lowers the temperature of the fixing roll. Then, when the temperature of the fixing roll becomes equal to or lower than the set temperature A, the temperature of the fixing roll is maintained near the set temperature A by repeating the above operation.

[0005]

During printing of the electrophotographic apparatus, heat is taken from the fixing roll to fix an unfixed image. At this time, since the heat generated by the heater lamp A is not sufficient, the heater lamp B is provided and both heater lamps perform the same operation. On the other hand, the heat taken from the fixing roll is small during non-printing. Therefore, when the temperature of the fixing roll becomes equal to or lower than the set temperature A, the heater lamps A and B generate heat, and the fixing roll is heated. Even if it is stopped, the temperature of the fixing roll overshoots and becomes 30 to 40 ° C. higher than the set temperature A.

FIG. 6 shows the temperature distribution of the fixing roll at this time. In the heat generation region of the heater lamp B, the temperature is 240.
℃. The release layer on the surface of the fixing roll has a fluorine resin content of 23
If the temperature is higher than 0 ° C., the softening occurs and the scratch resistance becomes low. Therefore, when printing is started from this temperature, the release layer is damaged by the printing paper, and the fixing roll is likely to reach the end of its life. Further, when printing is started from this temperature, there is a problem that hot offset easily occurs.

Therefore, an object of the present invention is to maintain the temperature of the fixing roll in the vicinity of the fixing temperature, thereby prolonging the life of the fixing roll and preventing hot offset, and improving the reliability of the electrophotographic apparatus. .

[0008]

SUMMARY OF THE INVENTION The above object is to provide a fixing roll, a first heater lamp having a heat generating area provided in the fixing roll and having a length substantially equal to a width of a printing sheet, and the first heater lamp. A second heater lamp with the following heat generation area,
Fixing provided with a low temperature detecting element mounted on the same circumference of the surface of the fixing roll, a high temperature detecting element, and a sensor head which is provided in a non-contact manner so as to face the temperature detecting element and takes out a signal change of the temperature detecting element. In the apparatus, the set temperature of the high temperature detecting element is set to the fixing temperature of the fixing roll, the set temperature of the low temperature detecting element is set lower than the high temperature element, and the temperature of the fixing roll is set to the low temperature detecting element. Heating the first heater lamp and the second heater lamp until the temperature becomes higher than the temperature; and when the temperature of the fixing roll becomes higher than the set temperature of the low temperature detecting element, heat generation of the second heater lamp. And a step of stopping the heat generation of the first heater lamp when the temperature of the fixing roll becomes higher than the set temperature of the high temperature detecting element. It is achieved by performing the temperature control of the fixing roll.

[0009]

According to the present invention, the first heater lamp and the second heater lamp are independently operated according to the signals generated from the low temperature detecting element and the high temperature detecting element, and the temperature is higher than the set temperature of the low temperature detecting element. The fixing roll is heated rapidly until it reaches a certain temperature, moderate heating is performed at higher temperatures, and heating is stopped at temperatures higher than the set temperature of the high temperature sensor, so that the temperature of the fixing roll does not rise sharply and the temperature of the fixing roll is Maintained near the set temperature.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is an external perspective view showing the fixing roll, and FIG. 3 is a sectional view showing the fixing roll. A release layer 2 made of a fluororesin is formed on the surface of the fixing roll 1, and 2 is formed inside.
Book heater lamps 6 and 7 are provided. The heater lamp 7 has a heat generation area having the same length as the maximum print paper width, and the heater lamp 6 has a heat generation area shorter than the print paper width in the central portion of the print paper where the temperature drops greatly during printing. Fusing roll 1
On the same circumference of the surface, the fixing temperature of the fixing roll 1 is 200
A high temperature detecting element 4 having a set temperature of 2 ° C., a low temperature detecting element 3 having a lower temperature of 180 ° C. having a setting temperature 1, and a temperature detecting element 3 provided in a non-contact manner facing the temperature detecting elements 3 and 4, A sensor head 5 for extracting the signal change 4 is provided.

Next, the temperature control method of the fixing roll according to the present invention will be described with reference to FIG. When the temperature of the fixing roll 1 is equal to or lower than the set temperature 1, the high temperature detecting element and the low temperature detecting element emit signals. At this time, the sensor head 5 takes out a signal of one of the temperature measuring elements and then takes out a signal of the other temperature measuring element during one rotation time T of the fixing roll 1.
The above signal is input to a heater lamp control device (not shown) connected to the sensor head 5, and the heater lamps 6 and 7 are connected.
Heat at the same time. As a result, the temperature of the fixing roll 1 rises, and when it becomes higher than the set temperature 1, the low temperature detection element 3 does not emit a signal. At this time, the sensor head 5
Does not extract a signal during the time T after extracting one signal. The heater lamp control device judges this and stops the heat generation of the heater lamp 6. As a result, the fixing roll 1 gradually rises in temperature. When the temperature of the fixing roll becomes higher than the set temperature 2 and the high temperature detecting element and the low temperature detecting element stop emitting signals, the heater lamp control device judges this and stops the heat generation of the heater lamp 7.
As a result, the temperature of the fixing roll 1 decreases. And
When the temperature of the fixing roll becomes equal to or lower than the set temperature 2, the heater lamp 7 is caused to generate heat. By repeating the above operation, the temperature of the fixing roll is maintained near the set temperature 2 as shown in FIG. 4, and the fixing can be started at the optimum fixing temperature when printing is started. Thereby, hot offset does not occur, and the release layer 2 can secure sufficient scratch resistance.

[0012]

According to the temperature control method of the fixing roll of the present invention, the temperature of the fixing roll is maintained near the fixing temperature, so that the life of the fixing roll can be extended and hot offset can be prevented. The reliability of the electrophotographic apparatus can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a temperature control method for a fixing roll according to the present invention.

FIG. 2 is an external perspective view showing a fixing roll.

FIG. 3 is a cross-sectional view showing a fixing roll.

FIG. 4 is a diagram showing a temperature distribution of a fixing roll according to the present invention.

FIG. 5 is a diagram showing a temperature control method of a fixing roll according to a conventional technique.

FIG. 6 is a diagram showing a temperature distribution of a fixing roll according to a conventional technique.

[Explanation of symbols]

Reference numeral 1 is a fixing roll, 2 is a release layer, 3 is a low temperature measuring element, 4 is a high temperature measuring element, 5 is a sensor head, and 6 and 7 are heater lamps.

Claims (3)

[Claims] 1. A fixing roll, a first heater lamp having a heat generating area provided in the fixing roll and having a length substantially the same as a width of a printing sheet, and a second heat lamp having a heat generating area equal to or smaller than the first heater lamp. Heater lamp, a low temperature measuring element mounted on the same circumference of the fixing roll surface, a high temperature measuring element, and a sensor which is provided in a non-contact manner facing the temperature measuring element to take out a signal change of the temperature measuring element. In a fixing device including a head, the set temperature of the high temperature detecting element is set to the fixing temperature of the fixing roll, the set temperature of the low temperature detecting element is set lower than that of the high temperature element, and the temperature of the fixing roll is A step of causing the first heater lamp and the second heater lamp to generate heat until the temperature becomes higher than the set temperature of the low temperature detecting element, and the temperature of the fixing roll is set to the low temperature detecting element. When the temperature becomes higher, the step of stopping the heat generation of the second heater lamp and the step of stopping the heat generation of the first heater lamp when the temperature of the fixing roll becomes higher than the set temperature of the high temperature detecting element are included. A method for controlling the temperature of a fixing roll, which is characterized in that 2. The fixing roll according to claim 1, further comprising a step of causing the first heater lamp to generate heat when the temperature of the fixing roll becomes equal to or lower than a set temperature of the high temperature detecting element. Temperature control method. 3. The temperature control method for a fixing roll according to claim 1, wherein the temperature control is performed during non-printing.