JPH08248804A - Fixing control method in fixing device for image forming device - Google Patents

Abstract

PURPOSE: To prevent disconnection caused by a secular deterioration in the filament of halogen lamp and the deterioration and peeling of 'Teflon<(> R<)> ' on the surface of a fixing roller caused by high temp. by specifying the thickness of the fixing roller and the lighting time of the halogen lamp while standing by. CONSTITUTION: This fixing control method is one for making the thickness of the fixing roller 1<=1.5mm and the lighting time of the lamp wile standing by >=1.5 seconds. When the surface temp. of the fix roller 1 is lower than a set temp., a CPU 7 turns on the halogen lamp 1b as in the conventional manner when a device is operated in consideration of information from a driving controller 9 as well. When a signal showing that the device is in a standby state without being operated is inputted, the CPU 7 turns on the halogen lamp 1b for 1.5 seconds. Thus, the color temp. of the filament consisting of a tungsten wire of the halogen lamp becomes a high temp. of >=250 deg.C, so that a normal halogen cycle is repeated and the deterioration in the filament can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer or a facsimile machine, which comprises a fixing roller having a halogen lamp as a heat source therein and a pressure roller pressed against the fixing roller. And a fixing control method for the fixing device.

[0002]

2. Description of the Related Art In the above heat roller type fixing device, the temperature of a fixing roller having a heat source is controlled in order to perform stable fixing. A conventional control method will be described with reference to FIG.

In FIG. 5, a fixing roller 1 and a pressure roller 2 are arranged so as to press each other. Fixing roll
The la 1 is provided with a peeling layer 4 on the outer peripheral surface of a cored bar 3 made of aluminum or iron, and a heater 1a is provided therein. The surface temperature of the fixing roller 1 is detected by the temperature sensor 5, and the CPU 7 compares the surface temperature detected by the temperature sensor 5 with the temperature set by the temperature setting device 6. When the surface temperature of the fixing roller 1 is higher than the set temperature, the heater 1a is turned off, and when the surface temperature of the fixing roller 1 is low, the heater 1a is turned on.
The surface temperature of la 1 is kept constant. Pressure roller 2
Is provided with a cored bar 2a and an elastic layer 2b provided on the outer side thereof, and a sheet 8 carrying an unfixed toner image 8a is passed between a fixing roller 1 and a pressure roller 2. At that time, the toner image 8a is fixed.

It is generally well known that a halogen lamp is used as a heat source for the fixing roller and that the core metal 3 of the fixing roller 1 is thinned in order to save energy.

[0005]

The heat roller type fixing device using a halogen lamp as a heat source for the fixing roller has the following problems.

First, the structure of the halogen lamp and the halogen cycle as its operating principle will be described.

A halogen lamp 10 shown in FIG. 6 includes a bulb 11 made of a glass tube and a filament 1 made of a tungsten wire disposed inside the bulb 11 via a supporter 12.
3, an internal lead wire 14 connected to both ends of the filament 13, and contact portions 15 at both ends. Valve 1
A halogen gas is enclosed in the unit 1.

When the halogen lamp 10 is turned on and the filament 13 reaches a high temperature, tungsten evaporates from the filament 13 and reacts with halogen gas to produce a tungsten-halogen compound. This tungsten-halogen compound is carried to the vicinity of the filament by thermal convection, where it is decomposed into tungsten and halogen gas due to the high temperature, tungsten is precipitated in the filament, and the released halogen gas undergoes the next reaction again. repeat. This process is shown in FIG. White circles are halogens, small black circles are tungsten, and large black circles are tungsten-halogen compounds.

In the above case, the halogen gas concentration is appropriate, and the filament has a predetermined color temperature (250 ° C. or higher).
, The halogen cycle described above is repeated. On the other hand, when the color temperature of the filament is low (250 ° C. or less) and the evaporation amount of tungsten is small, excess halogen gas ions that cannot combine with tungsten ions will be present. The color temperature increases when the lighting time is long and decreases when the lighting time is short.

Halogen gas is a highly corrosive gas, but in the non-lighted state, the amount of gas enclosed in the glass tube is very small, so that the halogen gas hardly causes corrosion. However, the color temperature is 250 ℃ in the lighting state.
When the value is lower than the above, the ionized halogen gas is actively moved as described above, so that excess halogen gas ions hit the filament to accelerate its deterioration and eventually break the filament.

On the other hand, as described above, in order to save energy, the fixing roller has recently been thinned. In such a thin fixing roller, the surface temperature rises quickly, and if temperature control is performed with this configuration,
The lighting time of the halogen lamp during standby is short, about 0.5 ~
1.0 second, and as a result, for the reasons explained above,
There was a problem that the filament deteriorates with time and is broken.

On the other hand, if the halogen lamp is turned on for a long time during standby, the fixing roller is thin, so that the ripple becomes large and the maximum temperature becomes high as shown in the graph of FIG. However, there is a problem that the Teflon on the surface of the fixing roller deteriorates due to high heat and peels off.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems in a fixing device using a halogen lamp as a heat source in a thin fixing roller.

[0014]

According to the present invention, the above-mentioned problems are solved by a fixing control method in which the thickness of the fixing roller is 1.5 mm or less and the lamp lighting time during standby is 1.5 seconds or more. Will be solved by.

Further, in order to advantageously solve the above problems, the present invention proposes that, in the above fixing control method, the fixing temperature during standby is lower than the fixing temperature during sheet feeding.

[0016]

According to the first aspect of the invention, in the method of controlling the fixing temperature in the fixing roller having a wall thickness of 1.5 mm or less using the halogen lamp as the heat source, the halogen lamp lighting time during standby is 1. Because it took more than 5 seconds,
The color temperature of the filament made of the tungsten wire of the halogen lamp rises to 250 ° C. or higher, so that the normal halogen cycle is repeated and deterioration of the filament can be prevented.

According to the second aspect of the present invention, in the above fixing control method, the fixing temperature during standby is lower than the fixing temperature during sheet feeding, so the maximum temperature due to ripples decreases, and therefore the fixing roll. The Teflon on the surface of the fixing roller is not damaged, and the life of the fixing roller can be extended.

[0018]

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

The block diagram for controlling the fixing device according to the present invention shown in FIG. 1 corresponds to the conventional block diagram for controlling the fixing device described with reference to FIG. 5, and the same parts are designated by the same reference numerals and their description will be omitted. For short. The block diagram of FIG. 1 differs from that of FIG. 5 in that the drive controller 9 is connected to the CPU 7 and that the halogen lamp 1b is used as the heater 1a.

In FIG. 1, when the surface temperature of the fixing roller 1 is lower than the set temperature, the CPU 7 also inputs information from the drive controller 9, and when the apparatus is operating, it is the same as the conventional one. When the halogen lamp 1b is turned on and a signal indicating that the apparatus is not operating in the standby state is input, the program is set so that the CPU 7 turns on the halogen lamp 1b for 1.5 seconds.

In the graph of FIG. 2 showing the relationship between the bulb (glass tube) temperature of the halogen lamp and the halogen lamp lighting time, when the halogen lamp on time is 1 second, the bulb temperature is as low as 250 ° C. , On time 1.
In 5 seconds, the temperature rises to 330 ° C., which is within the temperature range in which no problem occurs.

The block diagram for controlling the fixing device shown in FIG.
It is the same as that of FIG. 1, but differs from this in the following points.
That is, two set temperatures are stored in the temperature setter 6, and when a signal indicating that the device is in the standby state and not operating is input, the CPU 7 calls the lower set temperature from the temperature setter 6, It is controlled by. FIG. 4 shows the state of the ripple at this low temperature, and it can be seen that the maximum temperature due to the ripple has dropped. Therefore, the Teflon on the surface of the fixing roller is prevented from being deteriorated.

When the apparatus starts operating, the higher normal temperature is set and the on-time of the halogen lamp 1b is shortened.

[Brief description of drawings]

FIG. 1 is a control block diagram used in a fixing control method according to the first aspect of the invention.

FIG. 2 is a graph showing a relationship between a bulb temperature of a halogen lamp and a lighting time of the halogen lamp.

FIG. 3 is a control block diagram used in the fixing control method of the present invention.

FIG. 4 is a graph showing a temperature ripple state of the fixing roller at a low temperature in the second aspect of the invention.

FIG. 5 is a control block diagram used for conventional fixing control.

FIG. 6 is a vertical sectional view for explaining a halogen lamp.

7 is a cross-sectional view of the halogen lamp of FIG. 6 illustrating the halogen cycle.

FIG. 8 is a graph showing a temperature ripple state at a high temperature.

[Explanation of symbols]

 1 Fixing Roller 1b Halogen Lamp 2 Pressure Roller 3 Core Roller for Fixing Roller 5 Temperature Sensor 6 Temperature Setting Device 7 CPU 8 Paper 9 Drive Controller 10 Halogen Lamp 11 Bulb (Glass Tube) 13 Filament

Claims (2)

[Claims] 1. A fixing device of an image forming apparatus comprising a fixing roller having a halogen lamp as a heat source therein and a pressure roller pressed against the fixing roller, wherein the thickness of the fixing roller is 1. A fixing control method, which is set to 5 mm or less, and a lighting time of a halogen lamp during standby is set to 1.5 seconds or more. 2. The fixing control method according to claim 1, wherein the fixing temperature during standby is lower than the fixing temperature during sheet feeding.