JPH01319081A - Fixing device for electrophotography - Google Patents

Abstract

PURPOSE:To perform highly accurate printing by detecting the temperature of printing paper after fixing and controlling the temperatures of a fixing heating plate and heat-pressure roller by comparing the temperature detecting output with respective reference values. CONSTITUTION:A paper 6 to which a toner image is transferred by means of a transferring device 5 is sent to a heat-pressure roller 8 after it is preheated by a fixing heating plate 7, and fixed. When the paper 6 is sent to the plate 7 and roller 8, the output signal of a temperature detector 10 installed to a stacker 9 is inputted to comparators 11 and 12, where the output signal is compared with respective reference values of the comparators 11 and 12 and the compared outputs are inputted to temperature control circuits 13 and 14. The control circuits 13 and 14 operate in accordance with respective compared outputs and control the plate 7 and roller 8 to the optimum temperatures. Therefore, the paper is always held in the optimum state and stable high-quality printed pictures can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a 1% electrophotographic fixing device, and particularly to a fixing device that controls the temperature of a heating section.

[Conventional technology]

FIG. 6 shows a diagram of the operating principle of a conventionally used electrophotographic printing machine. In the figure, 1 is a charger, 2 is a photoreceptor, 6 is light that forms an electrostatic latent image on the photoreceptor 2, 4 is a developer that supplies toner to the static N latent image, and 5 is a toner image that is formed on paper 6. 8 is a heating pressure roller that fixes the toner image on the paper 6 that has passed through the fixing heating plate 7; 9 is a paper folding device ( (hereinafter referred to as stacker).

When printing, the surface of the photoreceptor 2, which has been uniformly charged by the charger 1, is irradiated with light 6 such as a laser beam. Once the electrostatic latent image is formed, toner is supplied to the electrostatic latent image by the developing device 4 to perform development. The developed toner image is transferred onto a sheet of paper 6 by a transfer device 5, preheated by a fixing heating plate 7, and then fixed by a heating pressure roller 8. The sheet 6 that has been fixed is sent to the stacker 9 and folded to complete printing.

``Problems to be Solved by the Invention'' As mentioned above, the paper on which the toner image has been transferred is sent to the heating pressure roller via the fixing heating plate and is fixed thereon. When the temperature If increases, the temperature of the paper after fixing rises by 4 degrees, and the temperature inside the stacker exceeds the reference value and the toner that has been fixed has to be fixed again by elution 17. In other words, toner stick occurs.

Figure 4 shows the relationship between the far boundary temperature l't'T and the paper temperature.Since the paper temperature is not temperature controlled, it increases as the return temperature j [Tg increases. , and intersects with the toner stick area A at temperature TI.

In the case of a printing machine or a high-speed machine, contrary to the above, it is necessary to set the temperature of the heating pressure roller higher than that of a medium-low speed machine to avoid printing defects (cold offset) due to low temperatures.

5.: Figure b shows the relationship between the environmental temperature TR+ and the paper temperature when a Takatsuji printing machine is used and only the heating roll is temperature controlled.In this case, the toner stick area xA and the cold offset area B This indicates that both occur.

When the Fujigo printing machine is operated at such high speeds, printing defects occur in the high temperature and low temperature areas of the paper, so the heating plate and heating pressure roller are heated at a higher temperature than in the case of a medium speed machine. This may result in the need to control the temperature separately.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic fixing device that can control the paper temperature to a constant value after completion of fixing and obtain high-quality images.

[Means to solve the problem]

The present invention transfers a toner image formed on the surface of a photoconductor onto a sheet of paper, preheats this sheet with a fixing heating plate, and then fixes it through a heating pressure roller.After fixing, the sheet is conveyed to a sheet folding device. A fixing device for electrophotography to be stored includes a temperature detector for detecting the temperature of the paper after fixing, a plurality of comparators for comparing the output of the L degree detector with respective reference values, and the output of the comparator. The printer has a plurality of temperature control circuits that control the temperature of the fixing heating plate and the heating pressure roller, and achieves the purpose by enabling high-precision printing with sufficient fixing.

[Effect]

In the fixing device of the present invention, when the paper that has been fixed is stored in the stacker, if the paper humidity fluctuates, printing defects such as toner stains will occur. The temperature of the fixing heating plate and the heating pressure roll are controlled to a constant value by detecting the hot side (1) and comparing this detection signal with a reference value, so that the paper is always kept in the optimum condition. As a result, stable, high-quality images can be obtained.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an operational explanatory diagram showing an embodiment of the electrophotographic fixing device of the present invention. The same parts as in Figure 3 are 4-1.
11 has been done.

In the figure, a temperature detector is installed in the stacker 9, and an alarm is displayed when the detected value exceeds a certain value. il,
The second is a comparator that compares the output of the temperature detector with a reference value. 13 and 14 are temperature control circuits, respectively fixing heating plate 7
．． The paper 6 on which the toner image has been transferred by the transfer device 5 that controls the heating and pressing roller 8 is preheated by the fixing heating plate 7, and is sent to the heating and pressing roller 8 to be fixed. Since the output signal of the temperature sensor ℃ set to t+ is input to the comparator 11 and V, the comparator 11.
Reference numeral 12 compares each reference value with the reference value 1, and inputs the comparison output to the temperature control circuit 16 and the shellfish. Temperature control circuit 16
and Takeshi operate according to their respective comparative outputs.

The fixing heating plate 7 and heating pressure roller 8 are controlled to the optimum temperature.

Figure 2 shows the relationship between the environmental temperature TI and the paper temperature in this case.As shown in the figure, the paper temperature l is
-1j' The temperature is controlled at a constant temperature (with respect to the change in TI) O, indicating that stable fixing is performed without conflicting with either the toner stick area A or the cold offset area B.

In this example, the temperature of the fixing heating plate and the heating pressure roll is controlled by detecting the temperature change of the stacker. By controlling the fixing heating plate and the heating pressure roll, stable fixing can be performed even when paper sizes are different.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide an electrophotographic fixing device that controls the paper temperature after fixing heating to a constant value, prevents the occurrence of printing defects, and provides a high-quality printed image. can do.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the operation of an embodiment of the electrophotographic fixing device of the present invention, FIG. 2 is a paper temperature control characteristic diagram, FIG. 3 is an explanatory diagram of the operation of the conventional device, and FIGS. 4 and 5. 1 is a paper temperature change characteristic diagram with respect to environmental temperature of a conventional apparatus. 10. Charger, 25. Photoreceptor, 30. Light, 4°, developing machine, 59. Transfer device, 63. Paper, 71. Fixing heating plate, 80
．． Heated pressure roller, 91. Stacker, ℃1. Temperature detector, 11, η9. Comparator, 16°140. Temperature control circuit. Patent applicant's name Hitachi Koki Co., Ltd. Ka111 ÷ TE Figure 3, bottom □TE

Claims (1)

[Claims] 1. Transferring the toner image formed on the surface of the photoreceptor to paper,
In an electrophotographic fixing device in which the paper is preheated by a fixing heating plate and then fixed by passing through a heating pressure roller, and the paper is conveyed to a paper folding device and stored after fixing, the temperature of the paper after fixing is detected. a detector, a plurality of comparators that compare the output of the temperature detector with respective reference values, and a plurality of temperature control circuits that control the temperature of the fixing heating plate and the heating pressure roller based on the output of the comparator. An electrophotographic fixing device comprising: 2. The electrophotographic fixing device according to claim 1, wherein the temperature detector is installed within the paper folding device. 3. The electrophotographic fixing device according to claim 2, wherein the temperature detector includes a circuit that displays an alarm when the detected value exceeds a certain value.