JP2000330410A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To save energy by providing a superior electromagnetic replacement efficiency in radiation of heat in a heating roll. SOLUTION: In this device, an edge part of the heating roll provided with a heating element is constituted from a magnetic member and 2nd magnetic members 5 and 5' installed in an exterior direction of the roll facing the magnetic member, windings 3 and 3' that are wound to the 2nd magnetic member and connected to an AC power source and another set of windings 4 and 4' wound to edge part magnetic members 6 and 6' and conducted by the windings are provided, the heating element is divided into at least 2 heating element parts 7 and 8 that are independent of each other, the edge part magnetic members are separated to be independent of each other corresponding to each of the above and windings are wound to each separated edge part magnetic member.

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 a toner image on a recording material, the image forming apparatus uses a method in which the recording material is nipped and conveyed by a heating roller and a pressure roller. A heating / pressing type fixing device for fixing on a recording material "is generally used. As the heating roller, for example, Japanese Patent Application Laid-Open No. 53-50844 and
An "induction-type heat generating roller" as disclosed in JP-A-60-60975 is known.

In such an induction type heat roller, generally,
A high-frequency current is passed through an induction coil disposed inside to generate a magnetic flux in the heat generating roller, and the magnetic flux causes an induced eddy current to be generated in a conductive layer (core metal member) on an inner peripheral portion of the roller. A desired temperature (generally, about 180 ° C.) is realized on the roller surface by heat.

[0004]

However, first of all,
The magnetic member constituting the heat generating roller is arranged on the outer periphery of the induction coil. However, when the other magnetic members are not arranged on the side or inside of the coil, it hardly forms a closed magnetic circuit.
If an induction current is generated by the high-frequency magnetic flux in such a state, the magnetoelectric exchange efficiency is poor, and in order to supply the induction current required to bring the heating roller to a predetermined temperature, more high-frequency current is supplied to the induction coil. Therefore, a low induction current requires a long heating time. When a magnetic member is arranged on the side or inside of the induction coil, a closed magnetic path is formed and the magnetoelectric exchange efficiency is improved, but the heat capacity of the entire heating roller increases, and more high-frequency current is supplied to the induction coil. Otherwise, the heating roller cannot be brought to the predetermined temperature in a short time.

Further, the induction coil is disposed in the heat generating roller and is almost in a nearly sealed state, and its atmosphere is facing the inner wall of the roller. The induction coil is exposed to an atmosphere higher than the surface temperature of the heat-generating roller due to the influence of the radiant heat of the roller and also the self-heating of the coil itself, and the temperature of the induction coil is, for example, 200 to 250 ° C.
May reach high temperatures.

[0006] In the prior art, a bobbin on which an induction coil is wound is located in the internal space of the heat generating roller, and there is a restriction in reducing the diameter of the heat generating roller. Due to the above problems, in the conventional technology, the power supply to the induction coil is large, and a special material with high heat resistance must be selected as the wire material of the induction coil, and the heating roller has a larger diameter. The problems matched in terms of safety, durability, reliability and energy saving. In addition, as a result of the above-described configuration, the entire apparatus becomes large and expensive, which hinders the spread to induction heating type fixing apparatuses.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a fixing device which is excellent in magneto-electric exchange efficiency when heat is generated by a heating roller and can save energy.

[0008]

An object of the present invention is to provide a heating roller provided with a heating element, wherein an end of the heating roller is formed of a magnetic member, and a second magnetic member disposed outside the roller opposite to the magnetic member. A winding wound around the second magnetic member and connected to an alternating power supply, and another winding wound around the end magnetic member and guided by the winding. It is divided into at least two heating element portions which are independent from each other, and the end magnetic members are divided independently so as to correspond to each of the heating element portions, and windings are wound around each of the divided end magnetic members. It is solved by doing.

The end magnetic member and the winding wound around the end magnetic member are arranged at both ends of the roller, and are respectively provided with a plurality of independent outer magnetic members corresponding to the respective end magnetic members. It is effective that the line is disposed axially outward of the roller.

[0010] At least one heating element is capable of changing the amount of heat generated when the machine starts up and when the recording material is conveyed and fixed, and can be controlled so that only the heating element whose heat generation amount can be changed generates heat. Is preferred. Further, it is also possible to turn off the heating element portion disposed outside the roller range through which the recording material passes, and to turn on the heating element portion disposed in the roller range with an electric power obtained by adding a margin corresponding to the OFF. It is suitable.

[0011] Advantageously, the roller end winding and the outer winding are maintained at a constant distance by abutment of a sliding member. It is also preferable that at least one of the end magnetic member and its winding and / or the outer magnetic member and its winding is covered around.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described based on an example shown in the drawings. FIG. 1 shows a schematic front part of a fixing device according to an embodiment of the present invention in a partially sectional view, and an example of operation control will be described with reference to FIGS.

The surface of the cylindrical heating roller 1 which is pressed against the pressure roller 2 made of an elastic body in the axial direction and fixed to the unit side plate 10 via the bearing 11 is separated from the surface of the heating roller 1 such as Teflon (trademark). Heating elements 7 and 8 are formed on the inner side of the metal core via an insulating member. The central heating element 8 is formed in an area A corresponding to frequently used narrow transfer paper (for example, A4 vertical size paper), and the end heating element 7 is formed in a paper passing range outside the area A. These heating elements 7 and 8 are connected to the corresponding windings 4 and 4 ′ (the first winding 4 for the end heating element and the second winding 4 ′ for the central heating element). Independent magnetic members 6,
6 ′ (the first magnetic member 6 and the second magnetic member 6 ′). Separate independent windings 3, 3 'are provided at positions outside the heating roller 1 facing the windings 4, 4', respectively.
(The third winding 3 and the fourth winding 3 ') are separate magnetic members 5, 5'.
(Third magnetic member 5 and fourth magnetic member 5 ′).

The contact point is set so that the gap between the first winding 4 and the second winding 4 'and the third winding 4 and the fourth winding 3' facing each other becomes an optimum gap (1 to 3 mm). P
Is kept at a certain distance. A bobbin (slip member) 15 carrying a winding or a magnetic member outside the heating roller 1 so that the heating roller 1 does not thermally expand and damage the contact point P.
Is installed so that it can be flexibly moved in the axial direction by a spring 12. Further, the periphery is covered with a cover 14 so that a magnetic material (toner and carrier or the like) does not enter between the windings and the magnetic members facing each other.

In the example of operation shown in FIG.
When the in-switch is turned on, the surface temperature of the heating roller 1 is increased.
The heating resistor is detected by a thermistor 13 for detecting the temperature.
The initial temperature T₁° C (room temperature level: for example, 40 ° C)
It is determined whether it is below. T₁Heating element 8 if below ℃
Only (the area corresponding to the area A) is heated. One more
Fixed time t₀T within sec₂° C (temperature at which toner is fixed)
Temperature), and then wait until the central heating element 8 (area
A), end heating element 7 (outside area A, hereinafter referred to as area B)
) To control the temperature of the entire heating roller 1.
Where the integral time t ₀Fixing set temperature T within seconds₂℃ or less
If not, stop the machine
You. When the main switch is turned on, T₁Above ℃
If it is, the fixing set temperature T₂It is thermi whether it is above ℃
Is determined by the star 13 and T₂Same as above if above ℃
Then, the end heating element 7 and the central heating element 8 are controlled to generate heat. this
With such control, the transfer paper size
In other words, you can start up quickly.

In the operation example shown in FIG. 3, when a copy (print) signal is received, a machine operation condition (transfer paper width size in this case) is recognized. By heating only the central heating element 8 corresponding to the above, and additionally applying power for the end heating element 7 for the area B, it is possible to prevent the temperature of the heating roller from dropping during continuous copying. Therefore, it is possible to avoid a decrease in copy speed in anticipation of a temperature drop. In the case of a wide transfer paper size, both the central heating element 8 and the end heating element 7 generate heat corresponding to the areas A and B. By performing such control, it is possible to copy (print) by effectively utilizing the heat energy, and to save energy.

[0017]

According to the present invention, the heating element of the heating roller is divided into at least two independent heating element portions, and the end magnetic members are divided independently from each other so as to correspond to each of the heating element portions. A winding is wound around each of the end magnetic members to form an induction heating system, so that only the roller portion necessary for fixing can be heated, thereby achieving excellent magnetoelectric exchange efficiency and energy saving. be able to.

At least one heating element can change the amount of heat generated when the machine starts up and when the recording material is conveyed and fixed (at the time of rising> at the time when the recording material is conveyed and fixed), and generates heat only in the heat generating part whose heat generation amount can be changed. With such control, it is possible to start up the range requiring heating in a short time. Further, the heating element portion arranged outside the roller range through which the recording material passes is turned off, and the heating element portion arranged in the roller range is turned on by the power obtained by adding a margin corresponding to the off. If so, it is possible to supply the maximum power that can be used to heat the range that requires heating, prevent a temperature drop during continuous use, and secure stable fixing quality.

If the roller end windings and the outer windings are maintained at a constant interval by abutment of a sliding member, it is possible to obtain an optimum heat generation efficiency suitable for the supplied electric power. In addition, if at least one of the end magnetic member and its winding and / or the outer magnetic member and its winding is covered, the magnetic material of the toner or the carrier is interposed between the magnetic members which may hinder the induction heat generation. It can prevent accidents of getting in and prevent damage and deterioration of the winding.

[Brief description of the drawings]

FIG. 1 is a schematic front view of a fixing device according to the present invention, and a sectional view of an induction heating mechanism at both ends of a roller, which is a feature of the present invention.

FIG. 2 is a flowchart illustrating an example of operation control in the fixing device of FIG. 1;

FIG. 3 is a flowchart showing another example of operation control.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating roller 3, 3 'Outer winding 4, 4' End winding 5, 5 'Outer magnetic member 6, 6' End magnetic member 7, 8 Heating element 12 Spring 13 Thermistor 15 Sliding member

Claims (6)

[Claims] 1. A fixing device for fixing a toner image to a recording material by nipping and conveying the recording material between two rollers, wherein at least one of the two rollers includes a heating element on an inner peripheral wall of the cylinder. In the fixing device, an end of the roller having the heating element is formed of a magnetic member, and a second magnetic member disposed outside the roller facing the magnetic member; A winding wound and connected to an alternating power supply; and another winding wound around the end magnetic member and guided by the winding, wherein the heating elements are at least two independent heating elements. It is divided into body parts, and the end magnetic members are divided independently of each other so as to correspond to each of the body parts, and a winding is wound around each of the divided end magnetic members. Induction heating type fixing device. 2. A plurality of independent outer magnetic members, wherein the end magnetic members and the windings wound on the end magnetic members are arranged at both ends of the roller. The fixing device according to claim 1, wherein the winding and the winding are disposed outside the roller in the axial direction. 3. The heat generating unit is configured so that at least one heat generating part can change a heat generation amount at the time of machine start-up and at the time of recording material conveyance fixing, and can be controlled so as to generate heat only at the heat generation unit whose heat generation amount can be changed. The fixing device according to claim 1, wherein: 4. A heating element disposed outside a range of a roller through which a recording material passes is turned off, and a heating element disposed in the roller range is turned on by power obtained by adding a margin corresponding to the off. The fixing device according to claim 1, wherein the fixing is performed. 5. The fixing device according to claim 1, wherein the roller end winding and the outer winding maintain a constant interval by abutment of a sliding member. 6. The magnetic recording medium according to claim 1, wherein at least one of the end magnetic member and its winding and at least one of the outer magnetic member and its winding are covered. Item 6. The fixing device according to item 1.