JPS61269180A - Heat fixing roll - Google Patents

Abstract

PURPOSE:To make uniform the surface temp. of a heat fixing roll in each position of the axial direction and to prevent the generation of the uneven fixing of a toner by forming a heating resistance layer on the inside peripheral surface of a cylindrical core. CONSTITUTION:The heat fixing roll is formed by forming successively a binding layer 2, an insulating layer 3 and the heating resistance layer 4 by plasma spraying on the inside peripheral surface of the cylindrical core 1 and coating a releasable layer 5 on the outside peripheral surface of the core 1. The core 1 is made of an Al alloy and is projected with small-diameter parts at both ends. Said core is supported rotatably in parallel with the press roll in a copying machine body. The insulating layer 3 is used to insulate the layer 4 from the layer 1 and is formed of Al2O5, MgO, etc. The layer 5 is used to permit the easy releasing of copying paper and is formed of, for example, PFA resin.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a heat fixing roll for fixing toner on copy paper in an image forming apparatus such as an electrophotographic copying machine, facsimile machine, or printer.

Conventional technology Conventionally, there has been a heating fixing roll for fixing toner on copy paper, which has a heating element installed inside a cylindrical core to indirectly heat the outer peripheral surface of the cylindrical core. In order to improve the performance, some types have a heat generating layer provided on the outer peripheral surface of the cylindrical core.

When a heat generating layer is provided on the outer peripheral surface of a cylindrical core, Japanese Patent Application Laid-open No. 55-
As shown in Japanese Patent No. 72390, there is a device in which an old -○R wire is wound around the outer circumferential surface of a cylindrical core to allow current to flow through it, but the specific resistance is low and the layer thickness is thin, so it is not possible to heat it evenly. It's hard to do.

For this reason, as shown in JP-A-55-164880, graphite, carbon black, lead dioxide, etc. are combined with resin to obtain an electrical resistance composition, and this composition is coated on the outer peripheral surface of a cylindrical core. There is one in which a heat generating resistor layer is formed by applying a current to the heat generating resistor layer from ring-shaped terminals at both ends of the cylindrical core in the axial direction to generate heat.

Problems to be Solved by the Invention When a heating resistance layer is provided on the outer periphery of a cylindrical core, it is difficult to form the heating resistance layer with a uniform thickness at each position in the axial direction due to the material of the heating resistance layer. 0 If the heating resistance layer becomes non-uniform, the temperature at each position on the outer periphery of the cylindrical core becomes non-uniform, making it impossible to fix the toner on the copy paper with high precision. In addition, in order to make it easier to peel off the copy paper from the roll after the toner has adhered to a certain level, a release layer is attached to the outer periphery of the heat-generating resistor layer. The surface had to be processed, which took one step. Furthermore, power is supplied to the heating resistor layer via a ring-shaped terminal, but this type of power supply method requires extra space for the terminals at both ends of the roll, and the structure is complicated to ensure that power is not interrupted. There were problems such as:

Means for Solving the Problems The heat fixing roll of the present invention will be explained with reference to FIG. 1 corresponding to an embodiment.

The cylindrical core l has small diameter portions at both ends that are connected to the copying machine main body L.
An insulating layer 3 is provided on the inner peripheral surface of a cylindrical core l which is rotatably held within the cylindrical core 1, and a heating resistance layer 4 is provided on the inner periphery of this insulating layer. Note that if the bonding layer 2 is provided between the insulation R3 and the cylindrical core l, the insulation layer will easily adhere. The heating resistance layer 4 is
It is formed of a material containing alumina, magnesia, and one or more oxides of alumina and magnesia spinel, and a nickel-chromium alloy.

Conductive electrodes 6 are provided on the inner periphery of both ends of the heat generating resistor layer 4, and these electrodes come into contact with a conductive brush provided inside the cylindrical core to supply current to the heat generating resistor layer. . Furthermore, a releasable layer 5 is provided on the outer peripheral surface of the cylindrical core l so that the copy paper can be easily peeled off, forming a heat fixing roll. Electrodes 6 at both ends of the inner periphery of the heating and fixing roll are arranged in parallel with the heating and fixing roll to fix the toner onto the copying paper when the copying paper emerges from between the rotating pressure roll and the heating and fixing roll. When a current is applied to the heat-generating resistor layer 4, the heat-generating resistor layer becomes high temperature, and the heat is transmitted to the release layer 5 of the cylindrical core 1 via the insulating layer 3, thereby heating the surface of the heating fixing roll. In this way, the heat of the heating resistor layer 4 is transmitted to the surface of the heat fixing roll via the insulating layer and the cylindrical core l, so that the heat is dispersed before it is transmitted from the inner circumference to the outer circumference, and on the surface of the heat fixation roll, An embodiment of the heat fixing roll of the present invention in which the temperature is uniform at all positions and toner can be fixed evenly will be explained with reference to FIG.

The heat fixing roll includes a bonding layer 2, an insulating layer 3, and a heating resistance layer 4 sequentially formed on the inner circumferential surface of a cylindrical core l by plasma spraying, and a release layer 5 coated on the outer circumferential surface of the cylindrical core l. This is what I did. Further, cylindrical electrodes 6 are attached to the inner periphery of both ends of the heating resistance layer 4, and power is supplied to the electrodes 6 via a power supply brush (not shown).

The cylindrical core 1 is made of A1 alloy, has small diameter portions protruding from both ends, and is rotatably supported parallel to a pressure roll in the main body of the copying machine (not shown). The bonding layer 2 is to facilitate bonding of the insulating layer 3 to the inner peripheral surface of the cylindrical core l, and may be omitted depending on the material of the cylindrical core l and the insulating layer. It is for insulating between the resistance layer 4 and the cylindrical core l, and is made of Al105 lMgO or the like.

The heating resistance layer 4 is formed of a material containing an oxide of one or more of alumina, magnesia, and alumina-magnesia spinel, and a nickel-chromium alloy.

The release layer 5 is for making the copy paper easy to peel off, and is made of, for example, PFA resin.

Since the female layer is directly coated on the outer periphery of the cylindrical core, it can be easily coated on the outer periphery of the cylindrical core 1 that has achieved a surface performance of 1. When forming the heat generating resistor layer 4 on the outer periphery of the cylindrical core 1 and coating the outer periphery with the release layer 5 as in the past, the surface of the heat generating resistor layer is rough and needs to be molded to be smooth. However, when the heating resistance layer 4 is provided on the inner periphery of the cylindrical core 1 as in the present invention, this molding step is not necessary, and the manufacturing time can be reduced to about half.

Here, a heating state when a current is applied to the heat generating resistance layer of the heat fixing roll will be explained. In this case, the size of the cylindrical core l is as follows: outer diameter 32 mm, inner diameter 30 mm, axial length 27 mm.
The thickness of the bonding layer 2 is 501 Lm, the thickness of the insulating layer 3 is 170 gm, the thickness of the heating resistor layer 4 is 60 pm, M
The thickness of the moldable layer 5 was 20 m.

When a current of 600 W was applied to the heat-generating resistive layer 4 in the heating fixing roll thus formed, it took about 60 seconds for the temperature of the release layer 5 on the surface to reach 200°C.

Further, the surface temperature of the heat fixing roll was approximately uniform at each position in the axial direction, as shown in FIG. The broken line in FIG. 2 shows the temperature distribution when the heat generating resistor layer is provided around the outer periphery of the cylindrical core as in the conventional case, and it is not uniform. This is because the thickness of the heat generating resistor layer 4 is non-uniform. be.

Note that the present invention does not limit the materials, thicknesses, etc. of the heat generating resistance layer 4, mold release layer 5, etc. described in the above embodiments.
- Effects of the Invention As described above, in the heat-fixing roll of the present invention, the heat-generating resistance layer is formed on the inner peripheral surface of the cylindrical core, so the surface temperature of the heat-fixing roll is uniform at each position in the axial direction, and the toner is fixed. Since there is no unevenness and the releasable layer can be provided directly on the outer circumferential surface of one cylindrical core, it is possible to easily form a highly accurate coating film. Furthermore, the electrode for power supply to the heating resistance layer is
Since it is provided on the inner circumferential side of the cylindrical core, there is no need to use the outer circumferential surface for heating and fixing the toner as an electrode, and miniaturization is possible.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the heat-fixing roll of the present invention, and FIG. 2 is a graph showing the surface temperature at each position in the axial direction of the heat-fixing roll.

Claims (2)

[Claims] (1) In a heat fixing roll that fixes toner on copy paper, a release layer is provided on the outer circumferential surface of the cylindrical core, and a heating resistance layer is provided on the inner circumferential surface of the cylindrical core with an insulating layer interposed therebetween. A heating fixing roll characterized by: (2) The heating fixing roll according to claim 1, wherein the heating resistance layer is formed of a material containing one or more oxides of alumina, magnesia, and alumina-magnesia spinel and a nickel-chromium alloy.