JPS6061780A - Fuser temperature control method - Google Patents

Abstract

PURPOSE:To prevent a discoloration of a form left on a spare heating plate when printing is stopped, by controlling a surface temperature of the spare heating plate of the time when printing is stopped, lower than that in the course of printing. CONSTITUTION:In the course of printing, a PRINT-N signal is set to an L level, and a transistor 18 is turned on. In this case, a voltage VREF is divided by R2 and R3 of a resistance 15, and a surface temperature of a spare heating plate is controlled to a prescribed temperature. When printing is stopped, the PRINT-N signal is set to an H level, and the transistor 18 is turned off. In this case, the voltage VREF is divided by R2 and (R3+R4) of the resistance 15, therefore, the voltage becomes higher than that in the course of printing. Accordingly, the surface temperature of the spare heating plate is controlled to a lower temperature than that in the course of printing.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to temperature control of a fuser in an electrophotographic printing device.

FIG. 1 is an example of a diagram showing the principle of an electrophotographic printing apparatus. An outline of the principle will be explained below.

A laser beam emitted from a laser oscillator 1 is modulated according to dot data obtained by decomposing a character image. The modulated laser beam is caused to scan the surface of the photosensitive drum 3 by the rotating polygon mirror 2. Since the surface of the photosensitive drum 3 is uniformly charged in advance by the charger 4, an electrostatic latent image is formed on the surface of the photosensitive drum 3 every time the laser beam scans. The photosensitive drum 3 rotates at a constant circumferential speed, and its electrostatic latent image is conveyed onto the imager 5, where it is developed by sucking the toner in the developer holder. The developed surface of the photosensitive drum is conveyed to a transfer device 6. Paper 7 is paper feed) Rakuta 8
The sheet of paper is conveyed by the printer 6 and is traveling at a constant speed in front of the transfer device 6, and is pressed against the surface of the photosensitive drum 30 by the sheet pushing mechanism 9.

The toner image on the surface of the photosensitive drum carried in front of the transfer device 6 is transferred to the paper 7 by the transfer device 6, and the toner image on the paper is heated through a preheating plate 10 and further heated to a high temperature. Heat roll 11 and backup roll 1
2 and is thermocompression bonded to the paper.

The principle of the electrophotographic printing apparatus has been outlined above with reference to FIG.

In the fixing device of an electrophotographic printing device, the temperature of the light surface of the preheating plate 10 is greatly related to the fixability of the toner to the paper, so the temperature is detected using a temperature collector such as a thermistor. Controlled to maintain a constant surface temperature.

An example of a temperature control circuit for a pre-q11 heating plate according to the prior art is shown in FIG. The voltage V divided by the resistor 15' (R1) and thermistor 14 is compared with the reference voltage vR1, which is divided by the resistor 15's I R2 and R3, and when "r77 > vngp (rq degree is low)" teeth)
By setting the IEATORON-N signal to the LαV level, the heater is energized, and when TIi<vRE (when the temperature is high), the HEATORON-N signal is set to the high level to stop the energization of the heater. In this way, the heater is controlled to 0N10FFL, and the surface temperature of the preheating plate is controlled to be constant.

In the prior art, the preheating plate 10 is controlled as described above.
The surface temperature of the printer was controlled to the same temperature as during printing even in the idle state when printing was stopped, which caused the problem that discoloration of paper that was left on the preheating plate when printing was stopped was likely to occur in a short period of time. there were.

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to make it difficult for paper left on a preheating plate to discolor.

The present invention focuses on the fact that if the surface temperature of the preheating plate is lowered, paper left on the preheating plate will be less likely to discolor and become 2. The fM variation control method was devised to control the surface temperature of the plate to a low level.

An example of a specific embodiment of the present invention is shown in FIG.

During printing, the PRINT-N signal is set to LOW level to turn on the transistor 18. In this case, V.

Since the pressure is divided by R2 and R3 of the resistor 15 as in FIG. 2, the surface temperature of the preheating plate is controlled to the same temperature as in FIG. When printing is stopped, PRINT
-N signal to High level, transistor 18
turn off. In this case, ①REF is divided by R2 and (R3+R4) of the resistor 15, so it becomes a higher voltage than during printing. Therefore, the surface temperature of the preheating plate is controlled to be lower than that during printing.

As described above, by changing the reference voltage V during printing and when printing is stopped, the surface temperature of the preheating plate when printing is stopped can be controlled to be lower than during printing.

In the example shown in Figure R3, the surface temperature setting value of the preheating plate is changed during printing and when printing is stopped, but if the surface temperature setting value of the preheating plate is changed depending on the paper speed, it can be used as a preheating plate. Since the temperature of the heating element can be kept low, the life of the heating element can be extended. That is, in the case of thin paper, the surface temperature setting value is set lower than that in the case of thick paper.

Whether the paper is thin or thick is detected by a paper thickness detection mechanism (not shown), and a signal indicating thin paper is used as a PRINT-H signal shown in FIG. 3 to lower the surface temperature setting value. It works like that. In this application example, if the paper thickness can be detected in several stages, it can also be applied to switching between multiple setting values.

According to the present invention, the preheating plate surface temperature at the time of stopping printing is
Since the heating temperature is controlled to be lower than during printing, it is possible to prevent the paper left on the preheating plate from discoloring when printing is stopped. Furthermore, since the temperature of the heating element used in the preheating plate can be kept low, the life of the heating element can be extended.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the principle of an electrophotographic printing apparatus, and FIG. 2 is a preheating plate temperature control circuit diagram according to the prior art. FIG. 3 is a preheating plate temperature control circuit diagram according to the present invention. Name of patent applicant: Hitachi Koki Co., Ltd.

Claims (1)

[Claims] In a fixing device of an electrophotographic printing apparatus, the fixing device of an electrophotographic printing apparatus includes a preheating plate for heating the toner transferred onto the paper, and a temperature measuring element and a control circuit for controlling the surface temperature of the preheating plate to a constant level. A temperature control method characterized by making it possible to switch the surface temperature setting of a plate in one shift.