JP2000029336A - Induction heat generating type fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device by which the overheating of an induction coil is prevented in spite of heat generation caused by Joule heat on the surface of a roller. SOLUTION: As for the fixing device which fixes a toner image on a recording material by holding and carrying the recording material by a heating roller 25 and a pressure roller 2 and where the heating roller 25 is an induction type heat generating roller, a bobbin 11 holding an induction magnetic flux generating coil 13 disposed at the inside of the heating roller 25 consists of a cylindrical body whose both ends are opened, and a fan 30 where at least one long hole extended nearly in parallel with the axial direction of the cylindrical body is formed on the peripheral surface of the cylindrical body and air is forced to blow at the inside of the cylindrical body is disposed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device in an image forming apparatus such as an electrophotographic printer, a facsimile, and a copying machine.

[0002]

2. Description of the Related Art In an image forming apparatus using a toner for forming a visible image, in order to fix the toner image on the recording material, the recording material is nipped and conveyed by a heating roller and a pressure roller to transfer the toner image. A heating / pressing type fixing device for fixing on a recording material is generally used. As the heating roller, for example, an "induction type heating roller" as disclosed in JP-A-53-50844 is known.

[0003] In such an induction type heat roller, generally,
An induction magnetic flux is generated by an induction coil disposed inside, and an induced current due to the change of the induced magnetic flux is generated in a dielectric layer (core metal member) on the outer peripheral portion of the roller. Temperature.

[0004]

However, in the above-mentioned induction-type heat generating roller, a bobbin on which an induction coil is wound is located in an internal space of a metal core member directly in contact with the pressure roller, and the bobbin is electrically insulated. Because of the low thermal conductivity of the resin, the temperature rise of the coil was severe due to the radiant heat of the metal core member, and even exceeded the heat-resistant temperature of the insulating coating of the coil. .

In view of the above problems, an object of the present invention is to provide a fixing device capable of preventing the induction coil from being overheated despite the heat generated on the roller surface due to Joule heat.

[0006]

An object of the present invention is to provide a fixing device for fixing a toner image on a recording material by nipping and conveying the recording material between a heating roller and a pressure roller, wherein the heating roller is an induction type heating device. In the fixing device which is a roller, the problem is solved by the fact that the bobbin holding the induction magnetic flux generating coil disposed in the heating roller is a cylindrical body having both ends opened and made of a heat conductive material.

A fixing device for fixing a toner image to the recording material by nipping and conveying the recording material between a heating roller and a pressure roller, wherein the heating roller is an induction type heating roller. A bobbin holding an induction magnetic flux generating coil disposed in the heating roller is formed of a cylindrical body having both ends opened, and at least one bobbin extending on a peripheral surface of the cylindrical body substantially in parallel with an axial direction of the cylindrical body. The above problem can also be solved by forming a long hole and further providing a means for forcibly blowing air in the cylindrical body. The opening formed in the peripheral surface of the cylindrical body, along the direction in which the air flows, so that the air forcedly blown through the cylindrical body easily passes through, or at least easily replaces the air present in the opening facing the coil. That is, the shape is cut into a slender shape so as to be substantially parallel to the axial direction of the cylindrical body, whereby efficient cooling of the coil is realized.

It is advantageous if the bobbin is made of an electrical insulator. Further, it is preferable that the bobbin is formed of at least an outer layer in contact with the coil and a support thereof, the outer layer is formed of an electrically insulating resistor having good thermal conductivity, and the support is formed of a metal cylinder.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described based on an example shown in the drawings. 1 and 2 show a fixing device according to the present invention in a plane perpendicular to an axis and a front side, respectively. The heating roller 25 in pressure contact with the pressure roller 2 rotates clockwise on the surface shown in FIG.
I, the recording sheet S is nipped between the heating roller 25 and the pressure roller 2 and is conveyed in the direction of the arrow to form a toner image T.
I is fixed by heat and pressure. The rotation of the heating roller 25 is performed when the gear 21 fitted and fixed to the roller meshes with a drive gear (not shown) and the drive gear rotates. The core metal of the heating roller 25 is made of a magnetic material such as stainless steel or iron, and a release layer made of a fluororesin is provided outside the core metal.

An induction coil 13 of an induction heating device is provided inside the heating roller 25. The induction coil 13 is wound around the hollow bobbin 11 at an appropriate interval, and has lead wires 14 and 17 at both ends. These leads 14 and 17 allow the high frequency current to flow through the induction coil 13 from both ends. The insulation coating of the induction coil is made of a TEMP coat or colored white to improve the heat resistance of the coil itself. The bobbin 11 is held so as not to rotate by brackets 15 and 16 provided on a side plate of the toner image fixing device. Hollow bobbin 11 open at both ends
A fan 30 is disposed outside one end of the motor, and is controlled to rotate when the coil is energized.

During the fixing operation, a high-frequency current flows through the induction coil 13 of the core 10 of the heating roller 25, and the core of the heating roller generates heat by Joule heat accompanying the induction current. At this time, the inner surface of the core is at 180 to 200 ° C., and radiant heat is radiated inside the core. However,
In the above configuration according to the present invention, the bobbin 11 provided at the center of the coil 13 is made of aluminum (204 W / (m · K)) or stainless steel (16 W / (m · K)) whose surface is anodized. ) And carbon steel sheet (54W / (m
· K)), and further made of ceramic or silicon resin (0.6 to 0.8 W / (m · K)), which is a good thermal conductor, with both ends open and in the axial direction thereof as recognizable from FIG. It is formed as a hollow body having a plurality of elongated openings (slit-shaped elongated holes) that are not closed by the coil 13 along the longitudinal direction) and forcedly blown by a fan 30 disposed outside one end thereof. Therefore, the temperature rise of the coil 13 due to the radiant heat is suppressed.

As shown in FIG. 4, as another configuration of the core portion 10, the central cylindrical portion 41 is made of a highly rigid material made of a good heat conductor such as aluminum or iron, and a heat good conductor is provided outside the center cylinder portion 41 to provide excellent electrical insulation. A silicone rubber sheet 42 having a thickness of 0.5 mm to 2 mm is provided, and a coil 13 is wound around the outside thereof. In this case, the central cylindrical portion 41 is provided with a plurality of elongated openings as in the above example, and the corresponding opening in the rubber sheet 42 is set to be smaller than the elongated opening of the central cylindrical portion to secure insulation. I do.

[0013]

According to the present invention, since the bobbin holding the induction magnetic flux generating coil disposed in the heating roller is a cylindrical body having both ends open and made of a heat conductive material, the conventional heat conductivity is 0.1 mm. As compared with a bobbin made of a resin of 1 to 0.2 W / (m · K), the heat radiation of the coil portion is easier and the temperature rise of the coil can be prevented.

A bobbin for holding an induction magnetic flux generating coil disposed in the heating roller is formed of a cylindrical body having both ends opened, and extends on the peripheral surface of the cylindrical body substantially in parallel with the axial direction of the cylindrical body. At least one elongated hole is formed,
Furthermore, by providing a means for forcibly blowing air in the cylindrical body, it is easy to exchange the air forcibly flowing inside the bobbin with the air on the outside or the air in the elongated hole range, and the cooling efficiency of the coil is reduced. improves.

If the bobbin is made of an electric insulator, even if the insulating film of the coil is broken, the bobbin does not easily fall to the ground, and the safety of the device can be improved. If the bobbin is composed of at least an outer layer in contact with the coil and its support, and the outer layer is made of a thermally conductive electric insulation resistor, and the support is made of a metal cylinder, a relatively expensive electric insulation It is possible to limit the use of a good thermal conductor, which is advantageous in terms of cost.

[Brief description of the drawings]

FIG. 1 is a schematic side view of a fixing device according to the present invention.

FIG. 2 is a schematic front view of the fixing device of FIG.

FIG. 3 is a schematic perspective view of a bobbin forming a core.

FIG. 4 is a schematic front view of a core portion according to another configuration.

[Explanation of symbols]

 2 pressure roller 10 core part 11 bobbin 13 induction coil 14, 17 lead wire 15, 16 bracket 21 gear 25 heating roller 30 fan

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Tomotaka Takamura, Inventor 3-1 Shinmei-do, Nakaname, Shimada-cho, Shibata-cho, Shibata-gun, Miyagi 3-1 Tohoku Ricoh Co., Ltd. F-term (reference) 2C061 AP03 AP04 AQ06 BB17 BB19 BB27 CK08 CN08 2H033 AA24 BA29 BB13 BE06 3K059 AA10 AB00 AB10 AB19 AB20 AB23 AB27 AD10 AD26 AD34 CD44 CD48 CD52 CD63 CD77

Claims (4)

[Claims] 1. A fixing device for fixing a toner image on a recording material by nipping and conveying the recording material between a heating roller and a pressure roller, wherein the heating roller is an induction type heating roller. An induction heating type fixing device, wherein a bobbin holding an induction magnetic flux generating coil disposed in a heating roller is a cylindrical body having both ends opened and made of a heat conductive material. 2. A fixing device for fixing a toner image to the recording material by nipping and conveying the recording material between a heating roller and a pressure roller, wherein the heating roller is an induction type heating roller. A bobbin holding an induction magnetic flux generating coil disposed in the heating roller is formed of a cylindrical body having both ends opened, and at least one bobbin extending on a peripheral surface of the cylindrical body substantially in parallel with an axial direction of the cylindrical body. An induction heating type fixing device, characterized in that a long hole is formed, and a means for forcibly blowing air through the inside of the cylindrical body is provided. 3. The fixing device according to claim 1, wherein the bobbin is made of an electrical insulator. 4. The bobbin comprises at least an outer layer in contact with the coil and a support thereof, wherein the outer layer is formed of an electrically insulating resistor having good thermal conductivity, and the support is formed of a metal cylinder. The fixing device according to claim 1.