JPH1165352A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fixing device constituted so that fixation is not lowered even at the initial time of a print output action by controlling fixing temperature by turning on plural heating heaters at the initial time of the action and turning on only one heating heater after a fixed time elapses when the print output action is executed. SOLUTION: The heating heaters L1 and L2 are controlled by a control part 10 so as to be used according to the respective modes of a warming-up time, a print output time and a standby time. At the warming-up time, both of two heaters L1 and L2 are turned on by the control part 10 by turning on a power source switch 11. Then, the temperature of a heating roller is raised in a short time by using two heaters L1 and L2. When a print is outputted, the fixing temperature is controlled by controlling the heaters by the control part 10 so that two heaters L1 and L2 are used and turned on at the initial time of the action and only one heater L1 is used and turned on after the fixed time elapses. At the standby time, only the heater L1 whose electric power is small is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used in an image forming apparatus such as a copying machine or a printer, and a heating roller for heating and fixing an unfixed toner image carried on a sheet; The present invention relates to a heat roller fixing device provided with a pressure roller for pressing an unfixed toner image carrying surface of a sheet, and more particularly to a fixing device provided with two heaters inside a heating roller.

[0002]

2. Description of the Related Art An unfixed toner image transferred onto a transfer material (sheet) by a transfer means is heated and pressed between a heating roller and a pressure roller of a fixing device, and a toner image adhered on the sheet is removed. By heating to about 200 ° C., the sheet is fused and fixed on the sheet. The heating roller is a hollow metal cylinder having a heater such as a halogen lamp as a heat source inside, and the pressure roller, which is driven and rotated in opposition to this, is a soft roller with a sponge-like elastic layer provided on the outer periphery of a cored bar. It is. The fixing device contacts the heating roller,
Alternatively, the temperature is detected by a temperature sensor provided in the vicinity, and the heating roller is turned on / off so that the surface of the heating roller is maintained at a temperature suitable for fixing, for example, about 200 ° C.
F control is performed.

[0003] In order to shorten the warm-up time and raise the temperature to a predetermined temperature within a short period of time, the heating heater is set to 1k.
Large power of W or more is used. At the start of lighting of a heater that uses large power, a large inrush current occurs,
The power supply voltage is reduced, and the flickering of the fluorescent lamp or the voltage drop of the indoor wiring portion may cause malfunction of the electronic device. In order to reduce the number of times the heater is turned on and off, two heaters are provided inside the heating roller.

In this case, the two heaters are a heater having a relatively large electric power and a heater having a relatively small electric power. When the equipment is warmed up, that is, when the power of the equipment is turned on, the heating roller reaches a predetermined fixing temperature. Two heaters are used until heated, two or one of them is used when the apparatus is on standby (idling), and one heater with relatively large power is used during print output operation. Generally, the temperature of the fixing device is controlled by using only the fixing device.

[0005]

In equipment, a heater having a large electric power is used as a heating heater for the purpose of shortening a warm-up time. Limit (eg 1500
W), and electric power is required for driving the equipment, etc.
The total power of the two heaters is also restricted.

By setting the heating roller in a non-rotating state in which the heating roller does not rotate during warm-up, heat conduction from the heating roller to the pressure roller is much less than during rotation, and the heating roller is heated to the fixing temperature. The warm-up time can be reduced. However, at the initial stage of the print output operation, the surface temperature of the heating roller not only loses the heat amount to the sheet carrying the toner image passing therethrough by fixing, but also the heat amount of the heating roller is robbed by the pressure roller due to rotation. There is a problem in that the temperature of the heating roller is reduced, thereby lowering the fixing property.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing device in which two heaters are provided in a heating roller so that the fixing property does not decrease even at the beginning of a print output operation.

[0008]

An object of the present invention is to provide an image forming apparatus in which an unfixed toner image carried on a sheet is heated and fixed.
In a fixing device provided with a heating roller having two heating heaters and a pressure roller for pressing the sheet onto the heating roller, the heater lighting control during the print output operation is performed by using two heating heaters in the initial operation. This is achieved by a fixing device characterized by performing a fixing temperature control of turning on the light and turning on only one heater after a lapse of a predetermined time.

[0009]

FIG. 1 shows a configuration and a control circuit of an embodiment of a fixing device according to the present invention. However, the present invention is not limited to such a configuration and control circuit.

The heating roller 31 is a hollow metal cylinder having two heaters L1 and L2 as heat sources inside, and the outer periphery thereof is a hard roller covered with, for example, a fluororesin tube. The heating roller 31 is rotated by a driving motor M, and a temperature sensor S for detecting the surface temperature of the roller is provided at a position very close to the peripheral surface of the rotating heating roller 31.

A halogen lamp or the like is used for the heaters L1 and L2, for example, a 1000 W heater is used for the high power heater L1, and a 300 W heater is used for the heater L2 having a lower power than the heater L1. The total power is set so as to be within a generally used power supply capacity even when the two heaters L1 and L2 are turned on. A commercial power supply is used as a power supply for the heaters L1 and L2,
For example, in Europe, an AC power supply E of 50 Hz and 230 V is used as a power supply, and a heater circuit performs zero-cross lighting by a triac as an AC control element.

A pressing roller 32 is provided, which is pressed against the rotating heating roller 31 by an urging member such as a spring and is driven to rotate. The pressure roller 32 is a soft roller in which a sponge-like elastic body is provided on the outer periphery of a cored bar, and the outer periphery thereof is further covered with a fluororesin tube or the like.

At the time of a print output operation for performing a fixing operation,
Fixing a sheet carrying a toner image between a heating roller 31 that rotates at a predetermined speed at a surface temperature at a predetermined fixing temperature and a pressure roller that is elastically deformed by pressing to form a nip portion and is driven to rotate. Is performed. The fixing device according to the present embodiment is used in a copying machine having a medium-speed processing capability.
It has a fixing capacity of 30 to 40 copies per minute for recording paper of a size.

In the fixing device of the present invention, the heaters L1, L
The use of 2 is controlled by the control unit 10 according to each mode of warm-up, print output, and standby.
Then, the heating roller 3 detected by the temperature sensor S
The surface temperature of the heating roller 31 is communicated to the control unit 10, and the control unit 10 performs ON / OFF control of the heater in use to control the surface temperature of the heating roller 31 to a preset fixing temperature.

Next, the control by the control unit 10 in each mode of the warm-up, the print output operation, and the standby will be described in detail.

At the time of warm-up, in an image forming apparatus such as a copying machine equipped with the present fixing device, by turning on a power switch 11, the control unit 10 turns on both the heaters L1 and L2, thereby turning on the two heaters L1 and L2. By using the heaters L1 and L2, the temperature of the heating roller 31 can be increased in a short time. At this time, the amount of heat moves from the heating roller 31 whose surface temperature is rising to the predetermined fixing temperature to the pressing roller 32, and the time until the surface temperature of the heating roller 31 reaches the predetermined fixing temperature is prolonged. The control unit 10 stops the drive motor M that drives the heating roller 31 to rotate so that the heating roller 31 does not rotate. Pressing roller 3
When the roller 2 can be moved toward and away from the heating roller 31, the pressure roller 32 maintains the state separated from the heating roller 31.

The controller 10 continuously or intermittently detects the surface temperature of the heating roller 31 by the temperature sensor S, and when it detects that the surface temperature has reached the preset fixing temperature To, the warm-up mode is set. finish. If the copy button 12 is turned on during this warm-up,
When the warm-up is completed, the mode shifts to the print output operation mode. If the copy button 12 is not turned on, the mode shifts to the standby mode.

At the time of print output operation, in the fixing device of the present invention, the heater lighting control by the control unit 10 is performed by using two heaters L1 and L2 at the initial stage of the operation and heating one heater after a lapse of a predetermined time. The fixing temperature is controlled using only the heater L1. Further, the control unit 10 rotates the drive motor M via the heating roller drive unit 14,
The heating roller 31 connected to this rotates. When the pressure roller 32 can contact and separate from the heating roller 31, the pressure roller 32 is in a pressure contact state, and the pressure roller 32 rotates following the rotation of the heating roller 31.

On the other hand, in the image forming apparatus, the image forming means 13 is operated by the control unit 10, and the sheet P carrying the toner image by the transfer process is heated by the heating roller 31 and the pressing roller 3
The fixing is performed while the sheet 2 is nipped and conveyed.

In a conventional fixing device in which two heating heaters are provided in a heating roller, the fixing operation is performed using only a heating heater having a large electric power (the heating heater L1 in this embodiment). According to the study of the present inventors, however, after entering the stable state, the fixing is sufficiently performed by, for example, turning on and off one of the heaters L1 of 1000 W, for example. Roller 3
Since 2 is in a low temperature state, not only the sheet P, which is nipped and conveyed and fixed, is deprived of heat by the heating roller 31, but also deprived of heat by the pressure roller 32. For this reason, in the early stage of the fixing operation, replenishment of the amount of heat by using one heater L1 is not sufficient, and in the early stage of the operation, a fixing defect may occur. In the present invention, this problem is solved by using two heaters L1 and L2, and after a certain period of time when the temperature of the pressure roller 32 has risen to a certain degree, only one heater L1 is used. Is used to control the fixing temperature so as to cover the temperature decrease due to the fixing of the sheet P. FIG. 2 shows the state of the surface temperature of the heating roller 31 in the initial stage of the fixing operation. 1 L indicated by a dashed line indicates that when only one conventional heater L1 is used, and 2 L indicated by a solid line indicates 5 shows a temperature change when two heaters L1 and L2 according to the present invention are used. As is clear from FIG. 2, in the initial stage of the operation, the replenishment of the heat quantity is insufficient as shown by the curve L1, and the excellent effect of the present invention is recognized.

During the waiting period When the print output of a predetermined number of sheets is completed, or when a short time elapses after the print output is completed, the mode is shifted to the waiting period mode. In the standby mode, the heater L of low power is used.
The temperature of the surface of the heating roller 31 is controlled by the control unit 10 so that the temperature of the surface of the heating roller 31 is maintained at a predetermined temperature (not necessarily the same as the set temperature To at the time of fixing). The control unit 10 stops the rotation of the heating roller 31. The pressing roller 32 is a heating roller 3
When the pressure roller 32 can be moved toward and away from the roller 1, the pressure roller 32 moves to a position separated from the roller.

[0022]

According to the present invention, warm-up within a short time and stable printing operation can be maintained without substantially impairing the fixing performance of the apparatus. In addition, by appropriately changing the number of heaters used according to a mode such as a warm-up operation or a print output operation, the number of ON / OFF operations of the heaters can be reduced to reduce the flicker value.

[Brief description of the drawings]

FIG. 1 is a configuration and control circuit diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a state of a heater surface temperature in an early stage of a fixing operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Control part 11 Power switch 12 Copy button 13 Image forming means 14 Heat roller drive part 31 Heat roller 32 Pressure roller L1, L2 Heater S Temperature sensor M Drive motor

Continuing on the front page (72) Inventor Watari ▲ Nana ▼ Masayuki 2970, Ishikawacho, Hachioji-shi, Tokyo Konica Corporation (72) Inventor Kazuhiko Konica, Inc. 2970, Ishikawacho, Hachioji-shi, Tokyo

Claims (3)

[Claims] 1. A fixing device comprising: a heating roller having two heaters therein for heating and fixing an unfixed toner image carried on a sheet; and a pressure roller for pressing the sheet against the heating roller. In the apparatus, the heater lighting control at the time of a print output operation is performed by performing fixing temperature control in which two heaters are turned on in an early stage of operation and only one heater is turned on after a lapse of a predetermined time. apparatus. 2. The fixing device according to claim 1, wherein the heating roller is in a non-rotating state during warm-up of the fixing device, and temperature control is performed by turning on two heaters. 3. The fixing device according to claim 1, wherein only one heater is turned on when the fixing device is on standby to control the temperature.