JP3313503B2 - Toner fixing device - Google Patents

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 an electrophotographic copying machine, a facsimile, a printer and the like.

[0002]

2. Description of the Related Art In electrophotographic copying machines, facsimile machines, printers, and the like, there is an increasing demand for higher copying speeds and printing speeds. One of the factors that determine these speeds is that they are transferred onto plain paper or the like. That is, the toner image can be reliably fixed. In this toner fixing process, flash exposure, pressurization, heating, heating and pressurizing, and other various means are employed. For this reason, a method of applying heat and pressure (a combined use of heat and pressure) is generally adopted.

The toner fixing device of the heating and pressurizing system applies a heat and a pressure simultaneously by passing paper carrying a toner image between upper and lower rolls to fuse and fix the toner on the paper (a hot roll fixing system). ). Here, usually, the upper roll is a heat 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 the surface has a releasable property, or a release agent is applied to the surface to be used for fixing. You.

[0004] The length of the heat roll depends on the size of the fixing device and the copying / printing speed, but is about 200 to 1200 m.
A long halogen heater is arranged inside a heat conductive pipe made of aluminum, iron, etc., and heated by energizing.
However, this halogen heater has a power consumption of 300 to 8
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 necessary to melt and fix the toner on the paper. Further, since it is difficult to reduce the diameter of the heat roll, it is also difficult to reduce the size of the toner fixing device.

[0005]

The inventors of the present invention have conducted a lot of researches and studies on a heat roll. However, instead of a halogen heater used as a heat source of a conventional heat roll, a coil-shaped 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 this. However, in this case, the heating wire often comes into contact with the inner peripheral surface of the heating roll due to the movement of the heating wire due to the rotation of the heating roll, and the electricity flowing through the heating wire also flows to 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, a distance (d) is required between the metal pipe and the heating wire, and a temperature gradient exists between the surface temperature of the heating wire and the surface temperature of the metal pipe, so that the thermal efficiency, that is, the electrical efficiency is reduced. Has disadvantages. Also, it is difficult to reduce the diameter of the heat roll. SUMMARY OF THE INVENTION It is an object of the present invention to provide a toner fixing device in which a heat roll is sufficiently heated with low power and short warm-up. Still another object of the present invention is to provide a toner fixing device that can be made smaller.

[0006]

According to the present invention, there is provided 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 heat source as a heat source in a metal pipe. The heating wire 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 uniformly contacted with the inner peripheral surface of the metal pipe, and the layer containing polybenzimidazole is formed on the outer peripheral surface of the metal pipe. Is desirably 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.

Embedded image 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 ° C.
It is a heat-resistant thermoplastic resin having a temperature of 35 ° C., a non-adhesive and wear-resistant substance having a dynamic wear coefficient of 0.19 and a Rockwell surface hardness of 110 (K scale). The method for producing the PBI is disclosed in Japanese Patent Application Laid-Open No. 1-99818 and the like. Further, Cel of Hoechst Celazole Co.
commercially available as azole®
A liquid 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 coil-shaped heating wire disposed as a heat source in the center of the metal pipe 1, and this heating wire is covered with a layer mainly composed of PBI (for convenience). This is referred to as “covered coil-shaped 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 toner from adhering to the heat roll, and is excellent in heat resistance and abrasion resistance. Since the abrasion 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 polyamideimide, or a mixture of at least two of these compounds. The surface coat layer 7 is obtained by dissolving the surface coat layer material in an appropriate 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, a 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 the wire material of the coated coil-shaped heating wire 2, but is preferably a nichrome wire having a diameter of 0.05.
A size of about 2 mm is appropriate. The thickness of the layer mainly composed of PBI covering the coil-shaped heating wire is 0.5 to 1,
000 μm, preferably 2 to 30 μm. 1,00
If the thickness is larger than 0 μm, the thermal conductivity is lowered, which is inconvenient. If the thickness is smaller than 0.5 μm, dielectric breakdown may occur. In a layer mainly composed of PBI, 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 wires 2 are arranged so that the temperature distribution on the surface of the heating roll becomes uniform. Metal pipe 1
The coated coil-shaped heating wires 2 may be in contact with each other or may have some distance, but from the viewpoint of thermal efficiency, it is particularly preferable that they are in contact with each other. Coated heating wire 2 in metal pipe 1
In order to fix the position, the filler 3 may be arranged in the gap in the metal pipe 1. As the filler 3, a substance having electrical insulation and high thermal conductivity is used, and preferably, powder such as MgO is used.

The coated coil heating wire 2 is connected to the electrode. As shown in FIG. 1, an electrode / drive roll support 4 in which the support of the electrode and the hot roll is integrated may be used. By fixing the electrode / drive roll support 4 using the electrically insulating materials 5 and 6, the metal pipe 1 and the coated coil-shaped heating wire 2 can be fixed. Silicone rubber, ceramics, or the like can be used as the electrically insulating material.

In practice, in order to coat the coil-shaped heating wire with a layer containing PBI as a main component, PBI alone or PBI and other additives are mixed with, for example, DMAc, DMF, NMP, preferably DMAc or a mixed solvent thereof. A solution is prepared by dissolving in a mixed solvent of a terpene such as kerosene and a ketone such as MEK, and a coil-shaped heating wire is immersed and coated in the PBI-containing solution, and then dried at about 100 to 500 ° C. I just need. Heating wires that are not coil-shaped
After coating with a layer mainly composed of, the coil-shaped heating wire 2 may be manufactured by deforming this into a coil shape.

In the present invention, the surface of the pair of rolls is preferably formed of PBI, PTFE, or relatively hard silicone rubber in order to prevent toner from adhering. Also,
Various modifications of the toner fixing device of the present invention may be considered within the range having the above essence.

[0016]

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

Example 1 A PBI layer having a thickness of about 25 μm was applied to a coiled nichrome wire (heating wire) having a diameter of about 0.6 mm, and this was made of an aluminum pipe (inner diameter 6 mm, outer diameter 8 mm, length 29.5 cm).
The heat roll was made so as to be housed in such a manner as to securely and evenly contact the inner wall of the heat roll. The PBI-coated coiled heat roll was assembled into a fixing section of a printer device and heated, and 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, 100 W was required to bring the surface temperature of the hot roll to 150 ° C., and it took 20 seconds to reach 150 ° C.

Comparative Example 1 An experiment was conducted in the same manner as in Experiment 1 using a normal heat roll (having a diameter of 20 mm and a length of 29.5 cm) having a halogen heater as a heat source. And 40 seconds to reach 150 ° C.

[0020]

According to the present invention, it is possible to obtain a toner fixing device capable of warming up in a short time with low electric power, and it is possible to downsize the toner fixing device as the diameter of the heat roll is reduced. .

[Brief description of the drawings]

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

[Explanation of symbols]

REFERENCE SIGNS LIST 1 Metal pipe 2 Coated heating wire (coil heating wire coated with PBI) 3 Filler 4 Electrode / drive roll support 5 Electrical insulating material 6 Electrical insulating material 7 Surface coat layer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-298942 (JP, A) JP-A-4-318582 (JP, A) Japanese Utility Model Application No. 64-6667 (JP, U) Japanese Utility Model Application No. Sho 62- 16966 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/20 103 H05B 3/00 335 H05B 3/48

Claims (3)

(57) [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, wherein 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 heating wire is uniformly in contact with the inner peripheral surface of the metal pipe. 3. The metal pipe according to claim 1, wherein a layer containing polybenzimidazole is provided on an outer peripheral surface of the metal pipe.
The toner fixing device as described in the above.