JPH07244443A - Toner fixing device - Google Patents

Abstract

PURPOSE:To obtain a toner fixing device with a heat roll heated for the short warm-up time with low electric power by using a metallic pipe contg. a coiled heating wire disposed as a heat roll and coating the heating wire with a polybenzimidazole-based layer. CONSTITUTION:A metallic pipe 1 contg. a coiled heating wire 2 disposed as a heat source at the center is used as a heat roll. The heating wire 2 has been coated with a polybenzimidazole-based layer and the coated coiled heating wire 2 is disposed so that the temp. distribution of the surface of the heat roll is made uniform. The pipe 1 and the heating wire 2 are especially preferably kept in contact with each other from the viewpoint of thermal efficiency. In order to fix the position of the heating wire 2 in the pipe 1, packing 3 may be disposed in the gap in the pipe 1. The objective toner fixing device capable of warm-up for a short time with low electric power is obtd. and the size of this device can be reduced in accordance with the reduction of the diameter of the heat roll.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner fixing device used in electrophotographic copying machines, facsimiles, printers and the like.

[0002]

2. Description of the Related Art In electrophotographic copying machines, facsimiles, printers, etc., there is an increasing demand for higher copying speeds and printing speeds, and one of the factors that determines these speeds is transfer onto plain paper. That is, the toner image can be reliably fixed. Various methods such as flash exposure, pressurization, heating, heat pressurization, etc. are adopted in this toner fixing process. However, since most of the toner resin is styrene resin or polyester resin, the fixing reliability is high. Therefore, the method of applying heat and pressure (combined heat and pressure method) is generally adopted.

This heat and pressure type toner fixing device is a mechanism for melting and fixing the toner on the paper by simultaneously applying heat and pressure by passing the paper carrying the toner image between the upper and lower rolls (heat roll fixing system). ) Is adopted. Here, the upper roll is usually a hot roll, and the lower roll serves as a support roll or a counter roll. The heat roll melts the toner resin carried on the paper to adhere (fix) the toner to the paper, and at least its surface has peelability, or a release agent is applied to the surface for fixing. It

The heat roll has a length of about 200 to 1200 m, although it depends on the size of the fixing device and the copying / printing speed.
A long halogen heater is arranged inside a highly heat-conductive pipe of aluminum, iron, etc. of m to heat by energizing.
However, this halogen heater consumes 300 to 8 power.
It has a drawback that it is as large as 00 W and that it takes 40 to 60 seconds to obtain (warm up) the roll surface temperature required to melt and fix the toner on the paper. Further, since it is difficult to reduce the diameter of the heat roll, it is difficult to downsize the toner fixing device.

[0005]

The inventors of the present invention have conducted a lot of research and study on heat rolls. Instead of a halogen heater used as a heat source for a conventional heat roll, a coiled metallic heating wire is used. It has been found that the power consumption can be reduced and the warm-up time can be shortened by using it. However, in this case, due to the rotation of the heating roll, the heating wire often shakes and the heating wire comes into contact with the inner peripheral surface of the heating roll, and electricity flowing through the heating wire also flows into the metal pipe. Heat loss tends to occur. In order to avoid this, it is necessary to provide an insulating layer between the heating wire and the metal pipe and fill the metal pipe with an electrically insulating wire and a substance having high thermal conductivity. For this reason, the distance (d) is required between the metal pipe and the heating wire, and there is a temperature gradient between the surface temperature of the heating wire and the surface temperature of the metal pipe, and therefore the thermal efficiency, that is, the electrical efficiency is reduced. It has drawbacks. Further, it is difficult to reduce the diameter of the heat roll. An object of the present invention is to provide a toner fixing device in which a heat roller is sufficiently heated with a small amount of electric power and warming up in a short time. Further, another object of the present invention is to provide a toner fixing device which can be further downsized.

[0006]

In a toner fixing device for an electrophotographic copying machine, a facsimile or a printer having a heat roll and a counter roll according to the present invention, the heat roll has a coiled heat source as a heat source in a metal pipe. It is arranged, and its heating line is covered with a layer containing polybenzimidazole as a main component.

In the toner fixing device of the present invention, the surface of the coated coil-shaped heating wire is in uniform contact with the inner peripheral surface of the metal pipe, and a layer containing polybenzimidazole is formed on the outer peripheral surface of the metal pipe. Is preferably provided.

The polybenzimidazole (hereinafter referred to as "PBI") used in the hot roll of the present invention is a stable heterocyclic polymer, preferably poly-2,2 '-(m-phenylene represented by the following structural formula. ) -5,5'-Bibenzimidazole.

[Chemical 1] The number average molecular weight of this PBI is 2,000 to 1,000,
000, preferably 5,000 to 200,000,
This PBI has a long-term continuous use temperature of 350 ° C and a heat distortion temperature of 4
It is a heat-resistant thermoplastic resin at 35 ° C., and is a non-adhesive and wear-resistant substance having a dynamic wear coefficient of 0.19 and a Rockwell surface hardness of 110 (K scale). A method for producing this PBI is disclosed in Japanese Patent Application Laid-Open No. 1-99818 and the like, and further, Cel of Hoechst Celazole Co.
commercially available as azole (registered trademark) and P
A liquid material in which BI is dissolved in a solvent has also been developed.

An embodiment of a heat roll used in the toner fixing device of the present invention will be described with reference to FIG. However, they do not limit the scope of the invention. The heat roll used in the toner fixing device of the present invention has a coiled heating wire as a heat source arranged in the center of the metal pipe 1, and the heating wire is covered with a layer containing PBI as a main component (for convenience). , This is referred to as a "coated coil heating wire").

The metal pipe 1 is made of a metal or alloy such as aluminum, iron, stainless steel or copper, preferably aluminum. As mentioned above, it is more preferable that the surface coat layer 7 is provided on the outer peripheral surface of the metal pipe 1. More preferably, the surface coat layer 7 is a layer containing PBI. This prevents the toner from adhering to the hot roll and is excellent in heat resistance and abrasion resistance. Since the wear resistance is excellent, the thickness of the surface coat layer 7 can be reduced, and the thermal efficiency is improved. The layer containing PBI may further contain polytetrafluoroethylene (PTFE), a silicone compound, a polyimide, a polyamide-imide or a mixture of at least two of these compounds. The surface coating layer 7 is obtained by dissolving the surface coating layer material in a suitable solvent and applying the solution to the metal pipe 1 by a spray coating method or a dip coating method. By adjusting the concentration of the solution, the coat layer 7 having a desired thickness can be obtained.

A wire made of an alloy such as a nichrome wire or a single metal is used as a wire material of the coated coil heating wire 2, but a nichrome wire is preferable and a diameter of 0.05.
A size of about 2 mm is suitable. The thickness of the layer containing PBI as a main component that covers the coiled heating wire is 0.5 to 1,
The thickness is 000 μm, preferably 2 to 30 μm. 1,00
If it is thicker than 0 μm, the thermal conductivity is lowered, which is inconvenient. On the contrary, if it is thinner than 0.5 μm, dielectric breakdown may occur. In the layer containing PBI as a main component, in addition to PBI,
A fluorinated compound such as PTFE, a silicone compound, carbon or the like may be added.

The coated coil-shaped heating wire 2 is arranged so that the temperature distribution on the surface of the heat roll is uniform. Metal pipe 1
The covered coil-shaped heat generating wire 2 may be in contact with each other or may be slightly apart from each other, but in terms of thermal efficiency, it is particularly preferable to contact each other. Coated coil-shaped heating wire 2 in metal pipe 1
A filler 3 may be arranged in the gap in the metal pipe 1 in order to fix the position. As the filler 3, a substance having electrical insulation and high thermal conductivity is used, and powder such as MgO is preferably used.

The coated coil heating wire 2 is connected to an electrode. As shown in FIG. 1, the electrode / driving roll support 4 in which the electrode and the support for the heat roll are integrated may be used. By fixing the electrode / driving roll support 4 using the electrically insulating materials 5 and 6, the metal pipe 1 and the covered coil-shaped heating wire 2 can be fixed. As the electrically insulating material, a child using silicon rubber, ceramic or the like can be used.

Actually, in order to coat the coiled heating wire with a layer containing PBI as a main component, PBI alone or PBI and other additives may be used, for example, DMAc, DMF, NMP, preferably DMAc or a mixed solvent thereof, Dissolve in a mixed solvent of terpenes such as kerosene and ketones such as MEK to prepare a solution, immerse the coiled heating wire in this PBI-containing solution to coat it, and then dry it at about 100 to 500 ° C. Good. In addition, the heating wire that is not a coil is connected to the PBI.
After coating with a layer containing as a main component, this may be deformed into a coil shape to manufacture the coated coil-shaped heating wire 2.

In the present invention, it is desirable that the surface of the counter roll is also formed of PBI, PTFE or a relatively hard silicone rubber in order to prevent adhesion of toner. Also,
Various modifications of the toner fixing device of the present invention may be considered within the scope having the above-mentioned essence.

[0016]

EXAMPLES Next, the present invention will be described more specifically with reference to examples. Parts herein are by weight.

EXAMPLE 1 A coil-shaped nichrome wire (heat-generating wire) having a diameter of about 0.6 mm was coated with a PBI layer having a thickness of about 25 μm, which was an aluminum pipe (inner diameter 6 mm, outer diameter 8 mm, length 29.5 cm).
A heat roll was prepared so that it was housed so as to contact the inner wall of the container surely and evenly. When this PBI-coated coiled heat roll was incorporated into the fixing section of the printer and heated, it took 4 seconds to reach 150 ° C.

Example 2 An experiment was conducted in the same manner as in Example 1 except that the coiled nichrome wire coated with the PBI layer was separated from the inner wall of the aluminum pipe by a distance d (= 1.5 mm). As a result, it took 100 W to bring the surface temperature of the hot roll to 150 ° C., and 20 seconds to reach 150 ° C.

Comparative Example 1 An experiment was carried out in the same manner as in Experiment 1 using an ordinary heat roll (diameter 20 mm, length 29.5 cm) having a halogen heater as a heat source. As a result, a surface temperature of 150 ° C. was 500 W. It took 40 seconds to reach 150 ° C.

[0020]

According to the present invention, a toner fixing device which can be warmed up in a short time with a small amount of electric power can be obtained, and the toner fixing device can be miniaturized with a reduction in the diameter of the heat roll. .

[Brief description of drawings]

FIG. 1 is a schematic view of a heat roll of a toner fixing device of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Metal pipe 2 Coated heating wire (coil heating wire coated with PBI) 3 Filler 4 Electrode / driving roll support 5 Electrical insulating material 6 Electrical insulating material 7 Surface coating layer

Claims (3)

[Claims] 1. A toner fixing device for an electrophotographic copying machine, a facsimile or a printer having a heat roll and a pair of rolls, wherein the heat roll has a coiled heating wire arranged as a heat source in a metal pipe, A toner fixing device characterized in that a coil-shaped heating wire is covered with a layer containing polybenzimidazole as a main component. 2. The toner fixing device according to claim 1, wherein the surface of the coated coil-shaped heating wire is in uniform contact with the inner peripheral surface of the metal pipe. 3. The layer containing polybenzimidazole is provided on the outer peripheral surface of the metal pipe.
The toner fixing device described.