JPH05210336A - Fixing device for color copying device - Google Patents

Abstract

PURPOSE:To prevent fixing failure due to deficiency in quantity of heat from being caused even when the copying speed in monochrome copying is high speed and to prevent fixing failure due to lowering of heat roll temperature from being caused when copying is started. CONSTITUTION:Two pieces of heaters 14 and 15 with different electric power capacities are provided to the heat roll 12, and the surface temperature of the heat roll 12 is maintained at a second set temperature during standby between copying after being reloaded. Furthermore, during copying, since changeover is carried out between the heater 14 and the heater 15 at the time of color copying and monochrome copying, the heater 15 with a small electric power capacity is turned ON in the color copying where great electric power is consumed at a halogen lamp. Then, in the monochrome copying where the great electric power is not consumed by the halogen lamp, the heater 14 with the great electric power capacity is turned ON.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a color copying mode and a black and white copying mode which can be selected. In the color copying mode, the linear velocity of the photosensitive member forming a toner image is slower than in the black and white copying mode. The present invention relates to a fixing device in a color copying apparatus set as described above.

[0002]

2. Description of the Related Art As a color copying apparatus using the electrophotographic process of the above type, a toner image corresponding to an original image is formed on a photoconductor, and a transfer material is fixed on a transfer drum arranged to face the photoconductor. An apparatus is known in which the toner image is transferred onto the transfer material to form a copied image on the transfer material. As a color copying machine of this type, four developing devices containing yellow, magenta, cyan, and black developers are superposed on a transfer paper fixed on a transfer drum with toner images of three colors in the color copying mode. A full-color copying machine which uses a developing device containing a black developer when transferring and fixing with a fixing device to obtain a color copy and obtaining a black-and-white copy is also known.

In the above-mentioned color copying machine, when a document is exposed to a white light color such as a halogen lamp and the light reflected from the document is exposed to the photoconductor through a color separation filter, the photosensor has a low spectral sensitivity to the blue color and the halogen is low. Since the lamp has a small amount of spectral light, it is necessary to increase the light amount of the exposure lamp when performing bluish exposure. At this time, when the same exposure lamp is used for both black and white copying and color copying, a large voltage is applied to the lamp in order to obtain the necessary exposure amount during color copying, so the lamp current also increases.

By the way, when the copying machine is used with a general commercial power source, it must be housed within 100V15A. However, if a large amount of electric power is secured to the exposure lamp as described above, the electric power to the fixing heater becomes insufficient. Therefore, the amount of power supplied to the fixing heater is limited.

[0005]

In a color copying machine using a fixing heater having a limited amount of power supply, the copying speed is slowed to obtain a desired fixing property. In this case, there are few problems because the copying speed is inevitably slowed due to lack of sensitivity of the photoconductor and the amount of spectral light during color copying, but there is a demand for higher copying speed during black-and-white copying. The fixing device using the heater for heating has a problem that fixing failure occurs due to insufficient heat quantity.

Further, in the conventional fixing device composed of a heating roller and a pressure roller, the heating roller is controlled by the control means so that the surface temperature thereof becomes a predetermined set temperature both during copying and during standby for copying. However, since the pressure roller does not heat the heater and the heat conduction from the heating roller is poor, the temperature difference between the heating roller and the pressure roller becomes 50 ° C. or more. Therefore, when the heating roller and the pressure roller pair rotate at the same time when the copying is started, the temperature of the pressure roller sharply rises due to the heat accumulated in the heating roller, but the temperature of the heating roller does not change even if the heater is turned on. There is a problem that the amount of heat released is large and the amount of heat is lowered, resulting in defective fixing.

The present invention solves the above-mentioned conventional problems,
An object of the present invention is to provide a fixing device in a color copying apparatus capable of preventing fixing failure due to insufficient heat quantity even when the copying speed at the time of black-and-white copying is high, and also preventing fixing failure due to decrease in heating roller temperature at the start of copying. And

[0008]

The structure of the present invention for achieving the above object is as follows.

(1) It has a selectable color copying mode and a black-and-white copying mode, and is set so that the linear speed of the photoconductor forming a toner image is slower in the color copying mode than in the black-and-white copying mode. A fixing device provided in a color copying apparatus, comprising a heating roller heated by a heater and a pressure roller pressed against the heating roller, wherein the heating rollers have different power capacities.
Book heaters are arranged. A heater with a large power capacity is turned on when a black and white copy is made, a heater with a small power capacity is turned off, and a heater with a large power capacity is turned off and a heater with a small power capacity is turned on when a color copy is made. The fixing device in the characteristic color copying machine.

(2) In the fixing device of the color copying apparatus described in the above (1), a control means for controlling the surface temperature of the heating roller is provided, and the control means copies to the first set temperature during copying. A fixing device in a color copying apparatus, wherein the surface temperature of the heating roller is controlled to a second set temperature which is higher than the first set temperature during standby.

[0011]

According to the structure of (1), the heating roller is provided with two heaters having different electric power capacities, and the heater having a large electric power capacity is turned on and the heater having a small electric power capacity is turned on during black-and-white copying.
FF, the heater with large power capacity is OF during color copying.
F, since the heater with a small power capacity is turned on, it is possible to prevent fixing failure due to insufficient heat even if the copying speed during black-and-white copying is high.

According to the configuration of (2), the surface temperature of the heating roller is set to the first set temperature during copying by the control means and to the second set temperature higher than the first set temperature during the standby for copying. Is controlled, it is possible to prevent fixing failure due to the temperature drop of the heating roller at the start of copying.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic view of a color copying machine provided with a fixing device according to the present invention. In FIG. 1, a drum-shaped photoreceptor 1 is wound around a charging device 2, developing devices 3, 4, 5 and 6 containing black, cyan, magenta and yellow developers, and a fed transfer material. Transfer drum 7 fixed and fixed
And a cleaning device 8 and the like, and further the photoconductor 1
An optical system 9 is arranged above the image forming apparatus, and a fixing device 10 is arranged to the left of the transfer drum 7. In this color copier,
Color copy mode and monochrome copy mode can be selected by key operation. When the black-and-white copy mode is selected, the halogen lamp 11 serving as an exposure lamp illuminates the document, and the reflected light of the document causes the charger 2 through the optical system 9.
The photoconductor 1 charged to a high potential is exposed to form an electrostatic latent image on the photoconductor 1. This latent image is developed by the developing device 3 having a built-in black developer, transferred onto a transfer material which is wound around the transfer drum 7 and fixed in advance, and then the transfer material is separated from the transfer drum 7 and conveyed to the fixing device 10. To do.

As shown in FIG. 2, the fixing device 10 includes a heating roller 12 and a pressure roller 13, and the heating roller 12 has two heaters 14 and 15 having different electric power capacities, that is, a heater 14 having a large electric power capacity. , A heater of 650 W and a heater 15 having a smaller power capacity than that, for example, 5
A 50 W heater is arranged. Then, the transfer material carrying the toner image is nipped and conveyed between the heating roller 12 and the pressure roller 13, and the toner image is fixed on the transfer material. Then, the sheet is discharged to a sheet discharge tray (not shown).

When the color copying mode is selected,
The basic operation is the same as in black and white copying, but the exposure operation by the halogen lamp 11 is reciprocated three times with cyan, magenta, and yellow with respect to the original. At this time, the color separation filter 16 for each color and the developing devices 4, 5 and 6 to be operated are switched.

Explaining the control system of the color copying machine, the main control unit 20 takes in input information from an operation unit (not shown) and sensor information of each unit from an input line 21 and processes them by an internal CPU to perform motor operation. , The load of the clutch and the solenoid is sequence-controlled by the output line 22, and at the same time, necessary information is sent to the AC drive control unit 23.
In the AC drive controller 23, the exposure halogen lamp 11 and the fixing motor (not shown) in response to an instruction from the main controller 20.
Control. Reference numeral 24 is a power supply unit.

In the color copying machine having the above-mentioned structure, when performing a black-and-white copy and a color copy by using the exposure halogen lamp 11 of one system, for example, if a halogen lamp having a rating of 80V and 320 W is used, the halogen lamp 11 is a lamp during copying. The constant voltage drive is performed by phase control so that the voltage becomes constant, but during black-and-white copying it becomes a constant voltage of about 50V.
An AC current of about 3A flows at 00V conversion.

On the other hand, at the time of color copying, the light having a constant wavelength is applied to the photosensitive member 1 by using a spectral filter. The halogen lamp 11 has a voltage of 70V to 80V and an AC current of 3.75A to 4A at a current of 100V conversion. Flows. here,
Since one transfer material passes through the fixing device 10 per one rotation of the transfer drum 7 during black-and-white copying, a heater with a large electric power must be used so that the temperature drop of the heating roller 12 does not occur in order to maintain good fixing performance. However, if a heater with a large power is used, a large amount of exposure power will be consumed during color copying, and the power consumption of the entire copying machine will exceed 100V15A, which can use a general commercial power supply.

Further, in the fixing device 10, the surface temperature of the heating roller 12 is controlled to a constant temperature. However, when the waiting time between copying becomes long, the heat conduction to the pressure roller 13 is poor and the pressure roller 13 is heated. Compared with the roller 12, the temperature becomes 50 ° C. or more lower. When copying is started from such a state, the heat of the heating roller 12 is transferred to the pressure roller 13 simultaneously with the rotation of the fixing device 10, the temperature of the pressure roller 13 rises, and the temperature of the heating roller 12 starts to fall, and the first copy However, there is a problem in that good fixing property cannot be maintained.

In order to solve such a problem, the fixing device 10 of the present invention controls the two heaters 14 and 15 arranged on the heating roller 12 with different electric power capacities as follows.
Here, the control sequence of the two heaters 14 and 15 arranged on the heating roller 12 and having different power capacities will be described with reference to the flowchart shown in FIG.

The heaters 14 and 15 are controlled by interrupting the CPU at the AC zero-cross timing. First, both the heaters 14 and 15 are turned off. This is a conventional means for omitting the OFF operation of each part by performing the OFF operation generated in each part of the flow upstream.

Next, the reload flag is checked, and if it is before the reload, the heaters 14 and 15 are turned on. Then, the surface temperature TH of the heating roller 12 and the first set temperature T
1, for example, 175 ° C. is compared, and if the surface temperature TH of the heating roller 12 is high, the reload flag is set. As a result, both heaters are turned off at the next zero cross timing.

According to this structure, since the heating roller 12 of the fixing device 10 contains the two heaters 14 and 15 having different electric powers, the time from the heating by one heater until the reloading after the power is turned on is increased. Can be shortened.

When the reload flag is set, it is checked whether copying is in progress. If copying is not in progress, that is, if it is in standby, the second temperature higher than the surface temperature TH of the heating roller 12 and the first set temperature T1 is reached. Of the set temperature T2, for example, 185 ° C., and if the surface temperature TH of the heating roller 12 is lower than the second set temperature T2, the heater 14 is turned on. If copying is in progress, the surface temperature TH of the heating roller 12 is compared with the first set temperature T1, and the heating roller 12
If the surface temperature TH is low, check whether it is a color copy or a black and white copy.
Is turned off, the heater 15 is turned on. For black and white copying, the heater 14 is turned on and the heater 15 is turned off.

Thus, the surface temperature TH of the heating roller 12
In the above control, since the two heaters 14 and 15 are turned on from the power-on to the first set temperature T1, the initial standby time can be shortened. After the reloading, if there is a waiting time which is between copying, the surface temperature TH of the heating roller 12 is set to the second set temperature T.
Since it is kept at 1, it is possible to prevent a fixing failure caused by a large amount of heat radiation to the pressure roller 13 at the start of copying. Further, since the heater 14 and the heater 15 are switched between the color copy and the black-and-white copy during copying, the heater 15 having a small power capacity is turned on during color copying which consumes a large amount of power to the halogen lamp 11. Further, the heater 14 having a large power capacity is turned on during black-and-white copying in which the halogen lamp 11 does not consume a large amount of power.

According to this structure, since the heater 14 having a large electric power capacity can be turned on at the time of black-and-white copying, the heating roller 12 can be sufficiently heated, and the linear velocity of the photoconductor 1 can be increased to increase the speed of black-and-white copying. Fixing failure does not occur.

[0027]

According to the above structure, in the present invention, the heating roller is provided with two heaters having different electric power capacities, the heater having large electric power is turned on, the heater having small electric power is turned off, and the color heater is turned off during black-and-white copying. During copying, the heater with a large power capacity is turned off and the heater with a small power capacity is turned on. Therefore, the power consumption of the halogen lamp and the heater is balanced, and the copying speed during black-and-white copying is high. It is possible to prevent fixing failure due to insufficient heat.

Further, according to the present invention, the surface temperature of the heating roller is controlled to the first set temperature during copying and to the second set temperature which is higher than that during copying standby, so that the heating roller temperature at the beginning of copying is controlled. It is possible to prevent fixing failure due to lowering.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a full-color copying apparatus of the present invention and its control system.

FIG. 2 is an explanatory diagram of a fixing device.

FIG. 3 is a flowchart showing a control flow of two heaters.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 10 Fixing device 11 Halogen lamp 12 Heating roller 13 Pressure roller 14, 15 Heater

Claims (2)

[Claims] 1. A color copying mode and a black-and-white copying mode which can be selected are set, and the linear speed of a photoconductor forming a toner image is set to be slower in the color copying mode than in the black-and-white copying mode. A fixing device provided in the color copying apparatus, comprising a heating roller heated by a heater,
In a fixing device including a pressure roller that is in pressure contact with the heating roller, two heaters having different power capacities are arranged in the heating roller, and a heater having a large power capacity is turned on and a heater having a small power capacity is turned on during black-and-white copying. A fixing device in a color copying apparatus, wherein a heater is turned off, a heater having a large power capacity is turned off, and a heater having a small power capacity is turned on during color copying. 2. The fixing device in the color copying apparatus according to claim 1, further comprising a control means for controlling a surface temperature of the heating roller, wherein the control means controls the surface temperature to a first preset temperature and stands by for copying. Is a fixing device in a color copying apparatus, wherein the surface temperature of the heating roller is controlled to a second set temperature which is higher than the first set temperature.