JPH0643782A - Fixing device for electrophotographic printing device - Google Patents

Abstract

PURPOSE:To provide a fixing device in which rise time until attaining fixing feasible temperature is shortened and the blot of a toner image is prevented. CONSTITUTION:The fixing device is provided with plural thermocouples 10 where two kinds of wire-state metal for performing heat generation and heat absorption in accordance with a current direction, that is, a copper wire 2 and a constatan wire 3 are brought into contact at respective one-side ends. Further, this device is provided with a heat roller 1 where the thermocouples 10 are internally set along a shaft direction so as to fix a toner image on a printing paper 8 by the generated heat of the thermocouples 10, a sensor 6 detecting the temperature of the roller 1, and a control part 7 controlling the direction and the magnitude of the current supplied to the thermocouples 10 in accordance with output from the sensor 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device, and more particularly to a fixing device in an electrophotographic printer.

[0002]

2. Description of the Related Art A fixing device using a heat roller 1 in a conventional electrophotographic printing apparatus shown in FIG. 2 is a heat roller 1 having a heater lamp 13 connected to a power source 14 therein.
Then, the toner image transferred onto the printing paper 8 is fixed by thermal pressing by the pressing roller 9 facing the heat roller 1. The surface temperature of the heat roller 1 is kept at about 120 ° C. by the heater lamp 13. Therefore, in order to prevent discoloration and smoke generation of the printing paper 8, the heat roller 1 and the pressure contact roller 9 are separated from each other during non-fixing,
It is necessary to bring the printing paper 8 into a pressure contact state at the start of fixing when the printing paper 8 starts to run.

A fixing device using a flash lamp 12 in a conventional electrophotographic printing apparatus shown in FIG. 3 is installed inside a flash lamp cover 11 and also has a power source 1.
The toner image transferred onto the printing paper 8 is fixed by causing the flash lamp 12 connected to the lamp 4 to emit light.

[0004]

In the above-mentioned conventional fixing device using the heat roller 1, it takes a start-up time until the heat roller 1 reaches a fixable temperature,
There are problems such as the meandering and wrinkling of the printing paper 8 due to the temperature difference between the both ends in the axial direction of the heat roller 1, and the bleeding of the toner image due to the pressure contact between the heat roller 1 and the pressure contact roller 9 or the pressure separation.

Further, in the above-mentioned fixing device using the flash lamp 12, there is a problem that when the print paper 8 is jammed, the print paper 8 smokes or ignites due to the emitted heat of the flash lamp 12.

[0006]

The fixing device in the electrophotographic printing apparatus of the present invention comprises a plurality of wire-like metals that generate heat and absorb heat in accordance with the direction of the electric current. Individual thermocouples, roller means for internally mounting these thermocouples along the axial direction and fixing the toner image on the printing paper by the heat generation of the thermocouple, detection means for detecting the temperature of the roller means, and Control means for controlling the direction and magnitude of the current supplied to the thermocouple according to the output of the detection means.

[0007]

An embodiment of the present invention will be described with reference to the drawings. Referring to FIG. 1 showing an embodiment of the present invention, each of a plurality of thermocouples 10 is formed by contacting two kinds of wire-shaped metal, a copper wire 2 and a constantan wire 3, at a contact point 5. . The other ends of the copper wire 2 and the constantan wire 3 are supported by the conductors 20 and 30 and connected to the DC power source 4, respectively. When a current is applied to each of these thermocouples 10 from the DC power source 4 in the direction of arrow A, heat is generated at the contact point 5 between the copper wire 2 and the constantan wire 3. When a current is applied from the DC power source 4 in the direction of arrow B, heat is absorbed at the contact point 5 between the copper wire 2 and the constantan wire 3. This phenomenon is called the Peltier effect, and its details are detailed in the Electronic Communication Handbook (No. 5) published by the Institute of Electronics and Communication Engineers in 1979.
See page 54). These thermocouples 10 are copper wires 2
The sensors 6 installed at both ends of the outer surface of the heat roller 1, which is inscribed in the heat roller 1 in a state where the contact point 5 between the heat roller 1 and the constantan wire 3 are in contact with the inner wall of the heat roller 1, detects the temperature of the heat roller 1. To detect. The control unit 7 controls the direction and magnitude of the current supplied by the DC power supply 4 according to this temperature. By passing an electric current in the direction of arrow A through the copper wire 2 and the constantan wire 3 of the thermocouple 10, heat is generated at the contact point 5 in contact with the heat roller 1, and the heat roller 1 is heated. The toner image on 8 is fixed by the heat roller 1 and the pressure roller 9 which are constantly in pressure contact. At the time of non-fixing, heat is absorbed at the contact point 5 by passing an electric current through the copper wire 2 and the constantan wire 3 in the direction of arrow B opposite to arrow A, so that the heat roller 1 discolors the printing paper 8. It is kept at a temperature that will not ignite.

Although the thermocouple 10 is composed of the copper wire 2 and the constantan wire 3 in the above-described embodiment, other metal that produces the Peltier effect may be used. Further, the heat roller 1 does not necessarily have to have a cylindrical shape such as a metal plate having a curvature.

[0009]

As described above, according to the present invention,
A plurality of thermocouples in which two types of wire-shaped metal that generate heat and absorb heat according to the direction of current are contacted at one end of each, and these thermocouples are internally installed along the axial direction to generate heat from the thermocouple. Roller means for fixing the toner image on the printing paper by means of the detecting means, detecting means for detecting the temperature of the roller means, and control means for controlling the direction and magnitude of the electric current supplied to the thermocouple according to the output of the detecting means. By providing the roller means (heat roller), the start-up time until the temperature reaches the fixable temperature is shortened, and bleeding of the toner image due to pressure contact between the heat roller and the pressure contact roller or separation is prevented. be able to. Further, it is possible to prevent the printing paper from smoking or igniting due to heat when the printing paper is jammed.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 2 is an example of a fixing device using a heat roller in a conventional electrophotographic printing apparatus.

FIG. 3 is an example of a fixing device using a flash lamp in a conventional electrophotographic printing apparatus.

[Explanation of symbols]

 1 Heat Roller 2 Copper Wire 3 Constantan Wire 4 DC Power Supply 5 Contact Point 6 Sensor 7 Control Section 8 Printing Paper 9 Pressing Roller 10 Thermocouple 20 Conductor 30 Conductor

Claims (1)

[Claims] 1. A plurality of thermocouples in which two kinds of wire-shaped metals, which generate heat and absorb heat according to the direction of electric current, are in contact with each other at one end, and these thermocouples are arranged in the axial direction. Roller means for fixing the toner image on the printing paper by the heat generation of the thermocouple, detecting means for detecting the temperature of the roller means, and the direction of the current supplied to the thermocouple according to the output of the detecting means, A fixing device in an electrophotographic printing apparatus, comprising: a control unit for controlling a size.