JPH0968885A - Heat fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent fixing defect, even if temp. drop of a heating roller occurs due to heat absorption by a recording paper, by detecting the temp. of the recording paper by a thermal sensor, and correcting the heating temp. of the heating roller corresponding to the detected temp. SOLUTION: This control circuit 11 is allowed to input respective output of the first temp. sensor 13 for detecting the temp. of the heating roller, and the second temp. sensor 16 for detecting the temp. of the recording paper contained for instance, in a paper feeding tray, into a arithmetic circuit 12, and while allowed to connect the output of computing circuit 12 with such as a halogen heater 10 incorporated in the heating roller and the a driving motor 17 for rotating a pressure roller. When power is applied, The arithmetic circuit 12 is allowed to detect the temp. of the heating roller by the output of the first thermal sensor 13, while detect the temp. of the recording paper by the out put of the second temp. sensor 16 for the instance, when the temp. of the recording paper is low, the set temp. of the heating roller is corrected, by setting the temp. for putting off and the temp. for turning on of the halogen heater 10 high.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat fixing device for fixing a toner image on a recording medium, such as a plain paper copying machine, a plain paper facsimile, and a printer, which uses an electrophotographic method.

[0002]

2. Description of the Related Art In copying machines using electrophotography,
After the electrostatic latent image is formed on the surface of the photoconductive photosensitive drum by charging and exposure, toner is attached to the electrostatic latent image to form a toner image, and the toner image is transferred to a recording medium such as paper. The toner image is fixed on the recording medium by a fixing device composed of a plurality of rollers.

In such an apparatus for fixing toner, the surface temperature of the heating roller is maintained at 150 to 190 ° C. This temperature control is performed, for example, in Japanese Patent Laid-Open No. 1-2217.
As disclosed in Japanese Patent Publication No. 80, a temperature sensor such as a thermistor is brought into close contact with the surface of the heating roller to detect the surface temperature of the roller, and when the surface temperature of the roller falls below 140 ° C., the heater is energized and the roller When the surface temperature reaches 170 ° C. or higher, the heater is deenergized to maintain the above temperature.

The heating roller has a conventional wall thickness of 2
A structure in which a halogen heater is arranged inside a metal pipe made of aluminum or the like having an outer diameter of about 25 mm and an outer diameter of about 25 mm is generally used. With the above conventional heating roller, preheating until the temperature reaches a predetermined temperature when the apparatus is started up. It takes a lot of time.

[0005]

Therefore, in recent years, by using a stainless steel pipe having a thickness of 0.2 mm or less and an outer diameter of 15 mm or less for a heating roller, power saving at the time of fixing and downsizing of a fixing device can be achieved. There is something measured, but in this case the surface temperature of the heating roller drops as soon as heat is taken because the heat capacity of the heating roller is small, and the surface temperature of the heating roller fluctuates greatly depending on the temperature of the passing recording paper. To do.

For example, the one shown in FIG. 5 has a wall thickness of 0.1.
When a heating roller made of stainless steel having a diameter of 2 mm and an outer diameter of 14 mm is used and a halogen heater of 300 W is used as a heat source, when the surface temperature of the heating roller is 147 ° C. or less, the halogen heater is turned on to heat the heating roller, Also 150
It is configured to turn off when the temperature exceeds ℃.

In the experiment, the surface temperature of the heating roller reaches 150 ° C. within 10 seconds after the start-up, which is much faster than the conventional one, but at t, the motor is rotated by feeding the recording paper on the surface of the heating roller. When the recording paper passes through, the heat of the heating roller is taken by the recording paper, and the surface temperature drops sharply to cause unfixed due to insufficient heating. When the toner of the recording paper adheres to the heating roller and the heating roller makes one rotation, the recording paper There is a problem that a so-called offset phenomenon that toner adheres to the toner occurs.

Therefore, an object of the present invention is to prevent a fixing failure due to insufficient temperature of the heating roller while using a thin and small diameter heating roller to shorten the warm-up time.

[0009]

SUMMARY OF THE INVENTION According to the present invention, a pressure roller is positioned to face one of thin-walled hollow cylindrical heating rollers having a built-in heater, and a control circuit controls energization of the heater so that the heating roller is predetermined. In the case where the recording paper is fed and fixed between the heating roller and the pressure roller while being heated to the temperature, a temperature sensor for detecting the temperature of the recording paper is provided, and the temperature is detected by the temperature sensor in the control circuit. The temperature correction means for correcting the heating temperature of the heating roller according to the temperature of the recording paper is provided.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an embodiment of the present invention will be described with reference to FIG. 1. Reference numeral 1 is an electrophotographic printer main body in which a paper feed device 3, a developing device 4, and a fixing device 5 are sequentially arranged in an outer case 2. It is arranged.

In the fixing device 5, as shown in FIG. 2, a rubber layer 8 of silicon or the like is provided on the surface of a core shaft 7 made of aluminum or the like above a heating roller 6 formed of a rod-shaped conductive ceramic. The pressure roller 9 is located oppositely.

The heating roller 6 has, for example, a plate thickness of 0.
It is made of a stainless steel pipe having a diameter of 12 mm and an outer diameter of 14 mm, and a halogen heater 10 for a heat source of, for example, 300 W is housed and arranged therein.

The halogen heater 10 is energized by a control circuit 11 shown in FIG. 3, for example.

The control circuit 11 has a first temperature sensor 13 composed of a thermistor or the like for detecting the temperature of the heating roller 6 at the input of an arithmetic circuit 12 composed of a microcomputer or the like.
And a second temperature sensor 16 composed of, for example, a thermistor for detecting the temperature of the recording paper 15 stored in the paper feeding tray 14 of the paper feeding device 3 or an infrared sensor, and is connected to the output thereof. A halogen heater 10 and a drive motor 17 for rotating the pressure roller 9 are connected, and the temperature of the heating roller 6 is detected by the output of the first temperature sensor 13 and the recording paper 15 is output by the output of the second temperature sensor 16. The temperature is detected, and on / off control of the halogen heater 10 is performed while the arithmetic circuit 12 corrects the set temperature of the heating roller 6 based on these temperatures.

Thus, for example, as shown in FIG. 4, when the power is turned on, the arithmetic circuit 12 detects the temperature of the heating roller 6 by the output of the first temperature sensor 13 and the output of the second temperature sensor 16. The temperature of the recording paper 15 is detected by, for example, when the temperature of the recording paper is low, the temperature at which the halogen heater 10 is turned off and the temperature at which the halogen heater 10 is turned on are set to be higher, and the drive motor 17 is rotated at T to perform recording. Even if the paper 15 is fed between the heating roller 6 and the pressure roller 9 and fixed, the heating roller 6
It is possible to perform stable fixing operation without causing defective fixing due to insufficient heat quantity.

In the temperature correction by the arithmetic circuit 12, it is preferable to set an appropriate correction temperature for each device because the heating degree of the recording paper 15 by the developing device 4 and the like varies depending on the device. When the temperature of the heating roller 6 is relatively high, the halogen heater 10 is turned off when the surface of the heating roller reaches the upper limit temperature of 155 ° C., for example, so that the surface temperature of the heating roller 6 becomes about 150 ° C. as in the conventional case. Surface temperature is 145
The control is performed so that the halogen heater 10 is turned on when the temperature drops to ℃.

[0017]

According to the present invention, the temperature of the recording paper is detected by the temperature sensor, and the heating temperature of the heating roller is corrected according to the detected temperature. When the temperature is low, the heating temperature of the heating roller is set to be high so that the fixing failure can be prevented even if the heating roller lowers the temperature due to heat absorption of the recording paper.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a printer using a fixing device according to the present invention.

FIG. 2 is a side vertical cross-sectional view of a main part showing an embodiment of the present invention.

FIG. 3 is a block diagram of a control circuit of the same.

FIG. 4 is also a characteristic diagram.

FIG. 5 is a characteristic diagram showing a conventional example.

[Explanation of symbols]

 6 Heating roller 9 Pressure roller 10 Halogen heater 12 Control circuit 15 Recording paper 16 Second temperature sensor

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hisao Shimizu 3-201 Minamiyoshikata, Tottori City, Tottori Prefecture Tottori Sanyo Electric Co., Ltd.

Claims (1)

[Claims] 1. A heating roller having a thin hollow cylindrical heating roller having a built-in heater is disposed so as to face one side of the heating roller, and the control circuit controls energization of the heating roller to heat the heating roller to a predetermined temperature. When a recording sheet is fed between the heating roller and the pressure roller to fix the recording sheet, a temperature sensor for detecting the temperature of the recording sheet is provided, and the recording detected by the temperature sensor is provided in the control circuit. A heating and fixing device characterized by comprising temperature correction means for correcting the heating temperature of the heating roller according to the temperature of the paper.