JP2010032572A - Temperature control method for fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a temperature control method for a fixing device, whereby temperature decrease of a heat roller is suppressed when printing starts and heat roller surface temperature required for printing can be maintained. <P>SOLUTION: The fixing device for a printer includes: the heat roller incorporating a heater; and a pressure roller disposed so that it can be brought into firm contact with the heat roller; and a temperature detecting means for detecting the surface temperature of the heat roller. The fixing device conveys long continuous belt-like paper with a toner image held thereon while sandwiching it under heat and pressure between the heat roller and the pressure roller at a firm contact part, and thereby fixes the toner image on the paper. In the fixing device, the surface temperature of the heat roller is detected by the temperature detecting means for a fixed period of time from the start of printing. On the basis of the transition of the surface temperature of the heat roller, a control time for turning on the heater at the start of subsequent printing is determined. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a temperature control method for a fixing device in an electrophotographic printing apparatus.

  In a printing apparatus using an electrophotographic system, a so-called heat roller system is frequently used as an apparatus for fixing an unfixed toner image on a sheet. This is achieved by sandwiching and transporting a sheet holding an unfixed toner image between a heating roller having a heater lamp built in as one heating source and a pressure roller provided so as to be in pressure contact with the heating roller. The toner image is heat-fixed. There is an optimum temperature for thermal fixing of the toner image, and the control unit detects the temperature of the heating roller so that an arbitrary temperature range including the optimum temperature is maintained, and the heater lamp is turned on or off. Is controlling.

Japanese Patent Laid-Open No. 9-80971

  By the way, in the printing operation, heat energy is generated by turning on the heater lamp, but the heat energy is deprived by the paper passing between the heating roller and the pressure roller. Therefore, in order to print while fixing the toner image on the paper, it is necessary to supply an extra portion of the heat energy taken away by the conveyed paper in addition to the heat energy necessary to melt the toner.

  For heater lamp ON / OFF control, when the surface temperature of the heating roller is lower than the control temperature required to fix the toner image on the paper, the heater lamp is not simply turned on, Control that maintains a stable temperature by turning on / off the control signal of the heater lamp is widely adopted. This ON / OFF ratio (hereinafter referred to as ON DUTY) is set so that the surface temperature of the heating roller is stably maintained at the control temperature during stable running.

  While printing is stopped, the pressure roller is not in pressure contact with the heating roller, and the paper is further stopped. In this state, the surface temperature of the heating roller is kept at the control temperature. Accordingly, since the heat energy is lost to the pressure roller and the conveyed paper at the start of printing, the surface temperature of the heating roller is temporarily greatly reduced. Due to this influence, there is a problem that a fixing failure occurs because the heat energy necessary for fixing the toner image on the paper to the paper cannot be supplied.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a temperature control method for a fixing device capable of suppressing a temperature drop of a heating roller at the start of printing and further maintaining a surface temperature of the heating roller required at the time of printing.

  In order to achieve the above object, the present invention comprises a heating roller having a built-in heater, a pressure roller provided so as to be able to press against the heating roller, and a temperature detecting means for detecting the surface temperature of the heating roller. In a fixing device of a printing apparatus, a long continuous belt-shaped sheet holding a toner image at a pressure contact portion between the heating roller and the pressure roller is nipped and conveyed while being heated and pressed, and the toner image is fixed on the sheet. The surface temperature of the heating roller for a certain period from the start of printing is detected by the temperature detecting means, and the control time for turning on the heater at the start of the next printing is determined based on the transition of the surface temperature of the heating roller. To do.

  According to the present invention, a fixing device that suppresses the temperature drop of the heating roller at the start of printing, can maintain the surface temperature of the heating roller required during printing without causing a fixing defect due to the temperature reduction. Temperature control method can be realized.

  According to the present invention, the problem in the prior art is that the state transition of the surface temperature of the heating roller at the start of printing is detected, and the heater lamp ON DUTY at the start of printing at the next printing is determined based on the data. It is solved by.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a heating and pressure fixing device used in an electrophotographic apparatus.

  The fixing device includes a pair of heating roller 2 and pressure roller 4 that can be pressed against each other, and a temperature detector 11 that faces the heating roller 2 and detects the temperature of the heating roller 2. In this embodiment, three temperature detectors 11 are arranged. The heating roller 2 is made of a metal core member made of metal and a releasable elastic body, and includes a heater lamp 3 as a heating source for heating the heating roller 2 inside.

  The temperature of the heating roller 2 is controlled by the control device 5 based on the output of the temperature detector 11. The temperature of the heating roller 2 is always detected by the temperature detector 11. The detected temperature detected by the temperature detector 11 is output to the control device 5, and the control device 5 turns on or off the heater lamp 3 based on the detected temperature. Here, if the surface temperature of the heating roller 2 that can be printed is defined as the control temperature, the output of the temperature detector 11 is compared with the control temperature in the control device 5, and as shown in FIG. When the surface temperature of No. 2 is low, the heater lamp 3 is not simply turned on, but the control signal of the heater lamp 3 is repeatedly controlled to be ON / OFF repeatedly, so that the control temperature is stably maintained. . The ON DUTY of the heater lamp 3 is a set value so that the surface temperature of the heating roller 2 is stably maintained at the control temperature during stable running.

  Although the temperature control described above is also performed at the start of printing, since the heat energy is lost to the pressure roller 4 and the conveyed paper at the start of printing, the surface temperature of the heating roller 2 is temporarily greatly reduced. .

  The temperature control method of the fixing device according to the present invention will be described. FIG. 4 is a temperature transition diagram of the heating roller surface temperature at the start of printing. The vertical axis represents the surface temperature of the heating roller 2 and the horizontal axis represents time. FIG. 2 is a block diagram of the control device 5 according to the embodiment of the present invention.

  A temperature control method of the fixing device will be described with reference to FIGS. 2 and 4. The surface temperature data of the heating roller 2 detected by the temperature detector 11 is sent to the main controller 12, and the main controller 12 determines whether the heater lamp 3 is ON / OFF based on the temperature data. The The main control unit 12 performs ON / OFF control of the heater lamp 3 via the heater lamp control unit 13.

From FIG. 4, usually the surface temperature of the heating roller 2 at the start printing is maintained at controlled temperature T _1. From the paper conveyance start at the start of printing (timing t ₁ in FIG. 4), and begins monitoring the surface temperature of the heating roller 2 by a temperature detector 11, the surface temperature of the heating roller 2 detected by the temperature detector 11 The data is sent to the main control unit 12. The monitoring of the surface temperature is performed during a period from the time when the surface temperature of the heating roller 2 decreases once to the return to the control temperature T ₁ (period from t ₁ to t _{2 in} FIG. 4). Here, the period during which the surface temperature of the heating roller 2 is detected is measured by the main control unit 12 using the timer 15. The lowest temperature among the monitoring period and T _2, the difference between the control temperatures T ₁ and temperature T ₂ and [Delta] T. Further, the time until the surface temperature of the heating roller 2 from the start sheet conveyance is restored to control temperatures T ₁ and Delta] t. By using the ΔT and Δt as parameters, an ON DUTY correction value of the heater lamp 3 at the start of printing at the next printing is determined from a preset ON DUTY correction table. FIG. 6 is a diagram illustrating an example of the ON DUTY correction table. The data of the ON DUTY correction table is arranged in the storage device 14 and read by the main control unit 12. The main control unit 12 determines correction data in the ON DUTY correction table from the above-described ΔT data and Δt data.

  FIG. 5 shows a state transition diagram of the surface temperature of the heating roller 2 to which the ON DUTY correction value thus determined is applied. The vertical axis represents the surface temperature of the heating roller 2, and the horizontal axis represents time. The above ON DUTY correction value is applied during a period from when the surface temperature of the heating roller 2 first falls below the control temperature to when the printing starts, until it rises to the control temperature again. Thereafter, the heater lamp 3 is controlled by the ON DUTY set for normal stable running. Thereby, the surface temperature of the heating roller 2 can be stably maintained at the control temperature.

  Since the control table value has different characteristics depending on the continuous amount of paper, thickness, paper width, and temperature / humidity and atmospheric pressure, a plurality of control tables may be set using each as a parameter.

  With the above control, it is possible to realize temperature control of the fixing device that suppresses the temperature drop of the surface temperature of the heating roller 2 at the start of printing.

  The present invention can also be applied to an apparatus having a heat source controlled at a high temperature and repeatedly stopping and driving.

1 is a schematic configuration diagram of a fixing device according to an embodiment of the present invention. 1 is a block diagram of a temperature control device of a fixing device according to an embodiment of the present invention. FIG. It is a surface temperature characteristic view of the heating roller during stable running. It is a surface temperature characteristic figure of the heating roller at the time of the printing start by a prior art. It is a surface temperature characteristic figure of the heating roller at the time of the printing start by this invention. It is a figure which shows an example of the ON DUTY correction table of a heater lamp.

Explanation of symbols

  2 is a heating roller, 3 is a heater lamp, 4 is a pressure roller, 5 is a control device, 11 is a temperature detector, and W is paper.

Claims (1)

A heating roller having a built-in heater; a pressure roller provided so as to be capable of being pressed against the heating roller; and temperature detecting means for detecting a surface temperature of the heating roller. In a fixing device of a printing apparatus for holding and conveying a continuous belt-like sheet having a long and continuous toner image while heating and pressurizing the toner image on the sheet,
The surface temperature of the heating roller for a certain period from the start of printing is detected by the temperature detecting means, and a control time for turning on the heater at the start of the next printing is determined based on the transition of the surface temperature of the heating roller. Method for controlling temperature of fixing device.

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