JPH07248699A - Method for controlling fixing for electrophotographic device - Google Patents

Abstract

PURPOSE:To prevent excessive melting, remelting and peeling of toner so as to make the printing quality stable by reducing the temperature of a preheater at the time of a slow speed printing, or at the time of printing on the other surface of a paper sheet whose one side has been printed. CONSTITUTION:When a printing speed is switched over to a low speed, or when printing is made on a paper sheet whose one side has already been printed for performing both surface printing, the temperature of a preheater 11 is reduced. That is, the temperature of the preheater 11 is voltage-transformed by means of a thermal sensor 16 and inputted to a comparator 2. A detected voltage and a reference voltage whith can be converted into optional temperature are compared with each other by the comparator 2, a heater is switched on when set temperature is not reached and it is switched off when the set temperature is reached. During low-speed printing, a low speed printing signal is outputted from a control part, a low speed printing transistor 4 is switched on and the reference voltage is changed. Also, during both surface printing, a both surface printing signal is outputted from the control part, a both surface printing transistor 3 is switched on and the reference voltage is changed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing control method for an electrophotographic apparatus.

[0002]

2. Description of the Related Art In a fixing device of an electrophotographic apparatus, conventionally, a heat roll having a heat source, a backup roll in pressure contact with the heat roll, a heat roll, and a printing roll provided on the upstream side of the backup roll in the paper conveyance direction are used. A fixing device including a preheater that performs preheating is known. Usually, the temperature of the preheater and the heat roll is detected by a heat sensor, and the control circuit controls the temperature to an arbitrary constant temperature.

[0003]

The temperatures of the preheater and the heat roll are determined by an amount of energy suitable for melting and fixing the toner image when the printing paper passes through the fixing device. Therefore, if the printing speed, that is, the speed at which the printing paper passes through the fixing device is faster than the reference speed, the energy required for the fixing is insufficient, and conversely, if the printing speed is slow, the energy is excessive. Therefore, in the electrophotographic apparatus capable of switching the printing speed, there is a problem that the toner excessively melts when the printing speed is switched to the low speed.

Further, in a double-sided electrophotographic apparatus for reversing a printing paper on which a toner image is printed and fixed on the front surface and printing on the back surface thereof, when the print-fixed toner image passes through a preheater, the toner image is printed. However, there is a problem in that the toner is re-melted and adheres to the preheater to hinder the conveyance of the printing paper, or the toner image on which printing and fixing has been carried out is peeled off to deteriorate the printing quality. Therefore, it is an object of the present invention to prevent excessive melting, remelting, and peeling of a toner image in an electrophotographic apparatus whose print speed can be switched or an electrophotographic apparatus which performs double-sided printing, and to stabilize print quality. That is.

[0005]

The above-mentioned object is to provide a heat roll having a heat source, a backup roll which is in pressure contact with the heat roll, and a preheating of the paper which is provided upstream of the heat roll and the backup roll in the paper conveyance direction. An electrophotographic device that has a fixing device with a preheater that can switch the printing speed,
This is achieved by lowering the temperature of the preheater.

Further, there is provided a fixing device having a heat roll having a heat source, a backup roll which is in pressure contact with the heat roll, and a preheater which is provided on the upstream side of the heat roll and the backup roll in the paper conveying direction to preheat the paper. In an electrophotographic apparatus capable of performing double-sided printing, this is achieved by lowering the temperature of the preheater when printing on the other side of a sheet on which one side has been printed.

[0007]

According to the present invention, by lowering the temperature of the preheater during low-speed printing, the amount of energy required for fixing can be optimally applied to the toner image on the paper, and the toner image does not melt excessively. . Further, by lowering the temperature of the preheater at the time of printing on the other side of the paper on which one side has been printed, the toner image printed on one side does not remelt or peel off.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view showing an embodiment of a fixing device to which a fixing control method according to the present invention is applied. The printing paper 15 to which the toner image is transferred from a not-shown photoreceptor is adsorbed by the suction 14 and the adhesion with the preheater 11 is enhanced. The printing paper 15 and the toner image are preheated by the preheater 11 and then sent to the heat roll 12 and the backup roll 13. Toner image is heat roll 1
2. It is heated and pressurized by the backup roll 13 and melted and fixed on the printing paper 15. The temperature of the preheater 11 is detected by the heat sensor 16, and the preheater 11 is controlled to an arbitrary constant temperature by a control circuit (not shown).

In the fixing device having such a structure, in the fixing control method according to the present invention, the preheater is used when the printing speed is switched to a low speed or when the other side of the paper which has been printed on one side is printed at the time of double sided printing. The temperature of 11 was lowered. This will be specifically described with reference to FIG. FIG. 2 is a control circuit diagram showing an embodiment of the fixing control method according to the present invention. The temperature of the preheater 11 is converted into a voltage by the thermal sensor 16 and input to the comparator 2. The detected voltage and a reference voltage that can be converted into an arbitrary temperature are compared by the comparator 2, and if the set temperature is not reached, the heater is turned on, and if the set temperature is reached, the heater is turned off. During low-speed printing, a low-speed printing signal is output from a control unit (not shown), the low-speed printing transistor 4 is turned on, and the reference voltage is changed. Also, during double-sided printing, a double-sided printing signal is output from the control unit (not shown), the double-sided printing transistor 3 is turned on, and the reference voltage is changed.

By performing the above control, the temperature of the preheater 11 is controlled by changing the reference voltage to an arbitrary temperature lower than the standard. A similar function can be obtained by using a selector for temperature switching and switching the comparator.

[0011]

According to the present invention, by lowering the temperature of the preheater during low-speed printing or printing on the other side of one-side printed paper, it is possible to prevent the toner from excessively melting, re-melting and peeling and to have a good fixing property. As a result, the print quality can be stabilized.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of a fixing device to which a fixing control method according to the present invention is applied.

FIG. 2 is a control circuit diagram showing an embodiment of a fixing control method according to the present invention.

[Explanation of symbols]

Reference numeral 2 is a comparator, 3 and 4 are transistors, 11 is a preheater, 12 is a heat roll, 13 is a backup roll, 14 is suction, 15 is printing paper, and 16 is a thermal sensor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Tsukasa Ogawa, 1060 Takeda, Katsuta-shi, Ibaraki, Hitachi Koki Co., Ltd. (72) Inventor, Satoshi Aida 1060, Takeda, Katsuta, Ibaraki, Hitachi, Ltd. (72) Inventor Isao Watanabe 1060 Takeda, Katsuta-shi, Ibaraki Hitachi Koki Co., Ltd. (72) Inventor Toru Kikuchi 1060 Takeda, Katsuta-shi, Ibaraki Hitachi Koki Co., Ltd.

Claims (2)

[Claims] 1. A fixing device comprising a heat roll having a heat source, a backup roll in pressure contact with the heat roll, and a pre-heater provided upstream of the heat roll and the backup roll in the paper conveyance direction to preheat the paper. A fixing control method for an electrophotographic apparatus, wherein the temperature of the preheater is lowered during low speed printing. 2. A fixing device comprising a heat roll having a heat source, a backup roll in pressure contact with the heat roll, and a preheater provided upstream of the heat roll and the backup roll in the paper transport direction to preheat the paper. A fixing control method for an electrophotographic apparatus, comprising: in an electrophotographic apparatus capable of performing double-sided printing, lowering the temperature of the preheater at the time of printing on the other side of a sheet on which one side has been printed.