JP2001117401A - Image fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make uniform the heating distribution of a paper passing part by preventing the temperature elevation of a paper non-passing part. SOLUTION: This device has an endless fixing belt 4, on the surface layer of which a mold-released layer is formed, to be revolved while being spread between a heating roller 1 composed of a conductive member and a fixing roller 2, on the surface layer of which an elastic layer is formed, an oil applying roller 5 for applying a releasing material to the fixing belt 3, first and second magnetic field generating means 7a and 7b installed near the heating roller 1 each for heating the heating roller 1 in the paper passing width areas of sheets in mutually different sizes with eddy currents, a pressing roller 3 provided to be press-contacted with the fixing roller 2 from the upside of the fixing belt 4 for forming a nip part in the gap between the fixing belt 4, and temperature detecting means 6 for detecting the temperature of the heating roller 1 heated by the magnetic field generating means 7a and 7b, and the heating roller 1 is heated by the magnetic field generating means corresponding t the size of a sheet to be passed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image fixing device used for an electrostatic recording type image forming apparatus such as a copying machine, a facsimile, a printer, and the like.

[0002]

2. Description of the Related Art In recent years, with the trend of energy saving of OA equipment, demands for energy saving and quick start of an image fixing device used for a printer, a copying machine, and the like are increasing. In order to meet the demand, a belt fixing type image fixing device using a fixing belt having a constant heat capacity has been proposed instead of a conventional general heat roller type image fixing device.

An image fixing apparatus of a fixing belt type will be described below.

FIG. 3 is a schematic view showing a conventional fixing belt type image fixing device.

As shown in FIG. 3, the conventional image fixing apparatus has a heating roller 1 on which a halogen lamp 8 as a heat source is mounted, and a fixing roller 2 having an elastic layer formed on a surface layer. A fixing belt 4 having a release layer formed on its surface is stretched between the heating roller 1 and the fixing roller 2. The fixing belt 4 is rotated by the rotation of the fixing roller 2.

[0006] An oil application roller 5 for applying a release agent to the fixing belt 4 is provided around the fixing belt 4.
And a temperature detecting means 6 for detecting the temperature.
Then, on / off control of the halogen lamp 8 is performed based on the detection signal output from the temperature detecting means 6 to heat the heating roller 1.

A pressure roller 3 is provided so as to press against the fixing roller 2 from above the fixing belt 4. Therefore, a nip portion is formed at a pressure contact portion between the pressure roller 3 and the fixing belt 4.

In the belt-fixing type image fixing apparatus configured as described above, it is not necessary to heat the fixing roller 2 having a large heat capacity, and it is sufficient to heat the heating roller 1 and the fixing belt 4 having a low heat capacity. It is possible to shorten the warm-up.

Conventionally, a halogen lamp 8, a resistance heating element, or the like has been used as a heating means for the heating roller 1. However, these have low heat generating efficiency due to their own heat capacity. . Therefore, as a heating means for further improving the heat generation efficiency, an electromagnetic induction heating method has been proposed.

Hereinafter, an image fixing apparatus using an electromagnetic induction system will be described.

FIG. 4 is a schematic diagram showing a conventional image fixing device using an electromagnetic induction heating system.

The image fixing device shown in FIG.
And a fixing roller 2 having an elastic layer formed on a surface layer. A fixing belt 4 having a release layer formed on its surface is stretched between the heating roller 1 and the fixing roller 2. And
The fixing belt 4 is rotated by the rotation of the fixing roller 2.

An oil application roller 5 for applying a release agent to the fixing belt 4 is provided around the fixing belt 4,
Detecting means 6 for detecting the temperature of the heating roller 1 via the
And are arranged.

In the vicinity of the heating roller 1, a magnetic field generating means 7a comprising a ferrite 7c and an exciting coil 7d is provided. In the magnetic field generating means 7a, energization to an exciting coil 7d is controlled by an exciting circuit (not shown) so that the fixing belt 4 maintains a constant temperature based on a signal output from the temperature detecting means 6. And the magnetic field generating means 7
The eddy current is generated in the conductive heating roller 1 in the magnetic field generated by a, and the eddy current is converted into heat (Joule heat) by the electric resistance of the heating roller 1, so that only the heating roller 1 generates heat.

A pressure roller 3 is provided so as to be in pressure contact with the fixing roller 2 from above the fixing belt 4. Therefore, a nip portion is formed at a pressure contact portion between the pressure roller 3 and the fixing belt 4.

In the image fixing device configured as described above, the heat generation efficiency is also improved, so that the warm-up can be further reduced. Further, since the warm-up can be reduced, it is not necessary to always warm the image fixing device to be in a standby state, so that power consumption can be reduced.

[0017]

In such an image fixing apparatus of the electromagnetic induction heating type, the magnetic field generating means is arranged over the maximum size width of the sheet, and the temperature distribution over the entire heating roller becomes uniform by energization. It is designed to be.

Therefore, when a sheet having a size smaller than the maximum size width is passed, the temperature is excessively increased because there is no heat loss due to the sheet passing in the non-sheet passing portion area.

As a result, when a large-size sheet is passed immediately after that, high-temperature offset occurs in a small-size non-sheet passing portion, and a paper wrinkle occurs due to an outer diameter difference (peripheral speed difference) due to thermal expansion. Or Further, if the fixing roller is idled while waiting for printing to absorb these temperature differences, there is a problem that printing productivity and the life of the roller and the belt are significantly affected.

Further, the magnetic field generating means also has a problem in that the temperature of the exciting coil rises due to a rise in temperature in the non-paper passing area, the magnetic permeability changes, and the amount of heat generated becomes unstable in the paper passing area.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image fixing device capable of preventing a temperature rise in a non-sheet passing portion and uniforming a heat distribution in the sheet passing portion.

[0022]

In order to solve this problem, an image fixing apparatus according to the present invention comprises a heating roller made of a conductive member, a fixing roller having an elastic layer formed on a surface layer, and a heating roller. An endless fixing belt with a release layer formed on the surface layer, an oil application roller that applies a release agent to the fixing belt, and a ferrite installed near the heating roller. A plurality of magnetic field generating means configured by the eddy current to heat the heating roller in the sheet passing width region of sheets of different sizes, each of which is configured by an excitation coil, and provided so as to be in pressure contact with the fixing roller from above the fixing belt. A pressure roller that forms a nip between the fixing belt and a temperature detection unit that detects the temperature of the heating roller heated by the magnetic field generation unit. The response to magnetic field generating means is obtained by a configuration to heat the heating roller.

The heating roller is heated by the magnetic field generating means only in a width corresponding to the size of the sheet to be passed through, so that only the width region corresponding to the sheet passing width region of the sheet has a uniform temperature distribution. Is no longer heated, the temperature rise in the non-sheet passing portion is prevented, and the heat generation distribution in the sheet passing portion can be made uniform.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to a heating roller made of a conductive member, a fixing roller having an elastic layer formed on a surface layer, and a heating roller and a fixing roller. An endless fixing belt with a release layer formed on the surface layer, an oil application roller that applies a release agent to the fixing belt, and a ferrite and an excitation coil installed near the heating roller A plurality of magnetic field generating means for heating the heating roller in the sheet passing width region of the sheets having different sizes by eddy current, and provided so as to be in pressure contact with the fixing roller from above the fixing belt; A pressure roller forming a nip portion, and a temperature detecting means for detecting a temperature of the heating roller heated by the magnetic field generating means, and a magnetic field generating means corresponding to a size of a sheet to be passed. This is an image fixing device that heats the heat roller, so that the non-paper-passing part is not heated, so that the temperature rise in the non-paper-passing part can be prevented and the heat distribution in the paper-passing part can be uniform. Has the effect of becoming

According to a second aspect of the present invention, in the first aspect, the temperature detecting means is an image fixing device for detecting a temperature of a heating roller in a heating area common to a plurality of magnetic field generating means. In addition, since the temperature of the heating roller heated by a plurality of magnetic field generating means can be measured by a single temperature detecting means, the apparatus has an effect that the apparatus can be simplified and the cost can be reduced.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In these drawings, the same members are denoted by the same reference numerals, and duplicate description is omitted.

FIG. 1 is a schematic diagram showing an image fixing device according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing a main part of the image fixing device of FIG.

The image fixing device shown in FIG. 1 is an image fixing device using an electromagnetic induction heating method, and has a heating roller 1 made of a conductive member and a fixing roller 2 having an elastic layer formed on a surface layer. An endless fixing belt 4 having a release layer formed on its surface is stretched between the heating roller 1 and the fixing roller 2. The fixing belt 4 is rotated by the rotation of the fixing roller 2.

Around the fixing belt 4, an oil application roller 5 for applying a release agent to the fixing belt 4, and a fixing belt 4
Detecting means 6 for detecting the temperature of the heating roller 1 via the
And are arranged.

In the vicinity of the heating roller 1, a first magnetic field generating means 7a and a second magnetic field generating means 7b comprising a ferrite 7c and an exciting coil 7d are provided.
These two magnetic field generating means 7a and 7b are controlled by a excitation circuit (not shown) to energize an excitation coil 7d based on a signal output from the temperature detection means 6 so that the fixing belt 4 maintains a constant temperature. You. Then, an eddy current is generated in the conductive heating roller 1 in the magnetic fields generated by the two magnetic field generating means 7a and 7b.
Is converted into heat (Joule heat) by the electric resistance, and only the heating roller 1 generates heat.

The pressure roller 3 is provided so as to be in pressure contact with the fixing roller 2 from above the fixing belt 4. Therefore, a nip portion is formed at a pressure contact portion between the pressure roller 3 and the fixing belt 4.

Here, as shown in FIG. 2, the first magnetic field generating means 7a is disposed so as to uniformly heat the large-size sheet passing width area of the heating roller 1, and the second magnetic field generating means 7b is provided. The heating roller 1 is disposed so as to uniformly heat the small-size sheet passing width area. That is, the first magnetic field generating means 7a and the second magnetic field generating means 7b are arranged so as to heat sheet passing width regions of different sizes.

When a large-size sheet is passed, the first magnetic field generating means 7a is energized and the heating roller 1 is turned on.
When the large-size sheet passing width area is heated and the small-size sheet is passed, the second magnetic field generating means 7b is energized to heat the small-size sheet passing width area of the heating roller 1.

The above-mentioned temperature detecting means 6 is installed at a position where the temperature of the heating area common to the first magnetic field generating means 7a and the second magnetic field generating means 7b can be detected.

In the present embodiment, two magnetic field generating means are provided, but it is necessary to provide the same number of sheets as the number of sheets to be passed, and the number is not necessarily limited to two. . That is, if the number of sheets to be passed is four, it is necessary to install four magnetic field generating means for heating the sheet passing width regions of these sizes.

As described above, according to the image fixing apparatus of the present embodiment, the first and second magnetic field generating means 7a and 7b corresponding to the large-size sheet passing area and the small-size sheet passing area are provided. Therefore, when a large size sheet is passed, the heating roller 1 has a uniform temperature distribution over the entire sheet passing width region, and when a small size sheet is passed, only the width region corresponding to the sheet passing width region of the heating roller 1 is uniform. It can be a temperature distribution.

As a result, since the non-sheet passing portion is not heated, it is possible to prevent a rise in the temperature of the non-sheet passing portion and to make the heat generation distribution of the sheet passing portion uniform.

Further, since the temperature detecting means 6 is disposed in an overlapping area of the two magnetic field generating means 7a and 7b, the heating by the single temperature detecting means 6 by the two magnetic field generating means 7a and 7b is performed. The temperature of the roller 1 can be measured, and the apparatus can be simplified and the cost can be reduced.

[0039]

As described above, according to the present invention, only the width of the heating roller corresponding to the sheet size to be passed is heated by the magnetic field generating means, and only the width region corresponding to the sheet passing width region of the sheet is heated. Since the temperature distribution is uniform, the non-sheet-passing portion is not heated, and the temperature rise in the non-sheet-passing portion is prevented, and the heat distribution in the sheet-passing portion can be made uniform. Effects can be obtained.

Further, if the temperature of the heating roller in the heating region common to the plurality of magnetic field generating means is detected by the temperature detecting means, the heating roller heated by the plurality of magnetic field generating means by the single temperature detecting means can be used. Can be measured, so that there is an effective effect that the apparatus can be simplified and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an image fixing device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating a main part of the image fixing device of FIG. 1;

FIG. 3 is a schematic view showing a conventional fixing belt type image fixing device.

FIG. 4 is a schematic diagram showing a conventional image fixing device using an electromagnetic induction heating method.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 heating roller 2 fixing roller 3 pressure roller 4 fixing belt 5 oil application roller 6 temperature detecting means 7a first magnetic field generating means 7b second magnetic field generating means 7c ferrite 7d exciting coil

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) H05B 6/14 H05B 6/14 F term (Reference) 2H033 AA03 AA09 BA11 BA12 BA25 BA27 BA32 BA43 BA44 BE06 CA07 CA17 CA27 CA48 3J103 AA02 AA90 BA43 FA01 GA02 GA57 GA58 GA60 3K059 AA08 AB28 AC33 AD25 AD34 CD19 CD79

Claims (2)

[Claims] A heating roller made of a conductive member; a fixing roller having an elastic layer formed on a surface layer; a heating roller and the fixing roller being stretched around and rotating around to form a release layer on the surface layer. An endless fixing belt, an oil application roller for applying a release agent to the fixing belt, and a ferrite and an excitation coil, which are installed near the heating roller and pass through sheets of different sizes. A plurality of magnetic field generating means for heating the heating roller in the paper width region by eddy currents; and a plurality of magnetic field generating means provided so as to be in pressure contact with the fixing roller from above the fixing belt to form a nip between the fixing belt and the fixing belt. A pressure roller; and a temperature detecting means for detecting a temperature of the heating roller heated by the magnetic field generating means, wherein the magnetic field generation means corresponds to a size of the sheet to be passed. An image fixing device, wherein the heating roller is heated by a producing unit. 2. The image fixing device according to claim 1, wherein said temperature detecting means detects a temperature of said heating roller in a heating area common to a plurality of said magnetic field generating means.