JPS58198071A - Heat fixation device - Google Patents

Abstract

PURPOSE:To reduce the thermal capacity of a fixation roll and to shorten the temperature rising time by pressing the fixation roll to a pressure roll by a pressure shaft which is inserted into the inside of the fixation roll and pressed against its inwall. CONSTITUTION:When the fixatio roll 1 is pushed toward the pressure roll 2 by the pressure shaft 6 having a high rigid factor which is inserted into the inside of the fixing roll 1 and pressed against its inwall, the fixing roll 1 is rotated by the frictional force between the pressure roll 2 and the pressure shaft 6. If current is made flow into a heating layer 1b of the fixation roll 1, the whole roll 1 is heated, but the strength of the fixation roll 1 against a load is not required so much. Consequently, the thickness of a ceramic cylindrical body 1a can be reduced, the thermal capacity of the fixation roll 1 can be reduced and the temperature rising time can be shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat fixing device for fixing toner on a toner support by heating and pressurizing the toner in an electronic copying machine, facsimile, or the like.

Conventionally, the fixing roller is composed of a fixing roller, a pressure roller disposed in contact with the fixing roller, and a pressure means for pressing the axes of the fixing roller and the pressure roller in a direction in which they approach each other. A heat fixing device is known in which a roller core is formed by a ceramic heater having a heat generating conductor embedded in a ceramic body, and an offset prevention film is formed on the outer surface of the roller core.

However, in this heating fixing device, the strength of the ceramic roller core against the load is low, so the roller core must be thick in order to withstand the specified load, so the heat capacity of the fixing roller is limited. Therefore, there is a drawback that the temperature rise time required to raise the outer surface of the anti-offset film of the fixing roller to a predetermined temperature becomes long.

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat fixing device that can eliminate the above-mentioned drawbacks.

The present invention is characterized in that a pressure roller is disposed so as to be in contact with the outer surface of a cylindrical fixing roller having a heat generating layer, and a pressure roller is inserted through the interior of the fixing roller and pressurized against the inner wall of the fixing roller. The purpose is to use the shaft to press the fixing roller against the pressure roller.

The present invention will be described in detail based on one embodiment illustrated below.

In FIG. 1, reference numeral 1 indicates a fixing roller. This fixing roller 1 has an electrically insulating ceramic cylindrical body 1.
a, a heat generating layer 1b formed on this outer surface, and an offset prevention film 1c formed on this outer surface.

The ceramic cylinder 1a is formed into a cylindrical shape by pressure sintering. The thickness of this ceramic cylindrical body 1a is approximately 1 mm to 3 mm. It is desirable that the ceramic cylinder 1a has a low thermal conductivity.

The heat generating layer 1b is formed on the outer surface of the ceramic cylindrical body 1a by a metallization process such as an ion blasting method using a metal such as nichrome or tungsten.

The thickness of this heat generating layer 1b is approximately 50 μm to 100 μm.

The offset prevention film IC is formed by applying Teflon, silicon, or the like to the outer surface of the heat generating layer 1b. The thickness of the offset prevention film IC is 7 μ≠ The pressure roller 2 is arranged so as to be in contact with the outer surface of the fixing roller 1. The pressure roller 2 is formed by forming a silicone rubber layer 2b on the outer surface of a core cylindrical body 2a made of metal such as stainless steel, iron, or aluminum(3)nium. This pressure roller 2 is fixed to a rotating shaft 3, and both ends of this rotating shaft 3 are supported by bearings 4, 4. A gear 5 is fixed to one end of the rotating shaft 3.

A pressure shaft 6 having a high rigidity is arranged so as to pass through the interior of the fixing roller 1 and come into pressure contact with the inner wall of the fixing roller 1. This pressure shaft 6 presses the fixing roller 1 in the direction of the pressure roller 2 and brings it into pressure contact therewith. Both ends of the pressure shaft 60 are supported by bearings 7, 7. A gear 8 is fixed to one end of the pressure shaft 6, and this gear 8 meshes with the gear 5. Gears 5 and 8 above
is rotated in a predetermined direction by a driving means (not shown), the pressure roller 2 and the pressure shaft 6 are rotated, and the fixing device is held in pressure contact with the pressure roller 2 and the pressure shaft 6. The roller 1 is also rotated by the frictional force between the pressure roller 2 and the pressure shaft 6. The above fixing roller 1
Guide members (not shown) are placed at both ends to guide the rotor when it rotates.

A power circuit (not shown) is connected to the heat generating layer 1b of the fixing roller 10, and when current is passed through the heat generating layer 1b by this power circuit, Joule heat is generated. The heat generated by the heat generating layer 1b heats the entire fixing roller 1, and its temperature rises.

The pressure shaft 6 is a ceramic cylinder 1a of the fixing roller 1.
The contact area is small and the ceramic cylinder 1a
Since the thermal conductivity of the fixing roller 1 is low, it has almost no adverse effect on the temperature rise of the fixing roller 1.

The toner is supported between the fixing roller 1 and the pressure roller 2 while the fixing roller 1 is kept at a temperature higher than a predetermined temperature and the fixing roller 1 and the pressure roller 2 are rotated. When the support body is inserted with the toner positioned close to the fixing roller, the toner is heated and melted, and is pressed and fixed to the toner support body.

Note that the fixing roller 1 may be formed by embedding a heat generating layer inside a cylindrical ceramic cylinder and forming an offset prevention film on the outer surface of the ceramic cylinder. In this case, since the thickness of the ceramic between the heat generating layer and the anti-offset film is about 50 μm at the thinnest, the anti-offset film IC is formed directly on the outer surface of the heat generating layer 1b as in the illustrated embodiment. This has the advantage that the heat capacity of the fixing roller can be reduced and the temperature of the heat generating layer does not need to be much higher than the temperature of the outer surface of the anti-offset film.

In the heat fixing device of the present invention, since the pressure shaft presses the fixing roller in the direction of the pressure roller and presses the fixing roller and the pressure roller, the fixing roller is not required to have much strength against the load. Since the thickness of the ceramic cylindrical body of the roller can be reduced, the heat capacity of the fixing roller can be reduced and the time required for the temperature of the fixing roller to rise can be shortened.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of the heat fixing device of the present invention, and FIG. 2 is a partially cutaway side view showing the same heat fixing device. 1... Fixing roller, 1a... Ceramic cylindrical body, 1
b...Heating layer, IC...Offset prevention film, 2...
・Pressure roller, 6... Pressure shaft (7) % (Figure % 2 Figure

Claims (1)

[Claims] A cylindrical fixing roller having a heat generating layer, a pressure roller disposed so as to be in contact with the outer surface of the fixing roller, and a pressure roller disposed so as to pass through the inside of the fixing roller and be in pressure contact with the inner wall of the fixing roller. A heating fixing device comprising a pressure shaft that presses a fixing roller against a pressure roller.