JPH08328409A - Thermal fixing roller - Google Patents

Abstract

PURPOSE: To prevent defective fixation caused by the temperature drop at a paper passing part in accordance with the size of a paper width and to prevent the occurrence of offset to the surface of a thermal fixing roller caused by that the temperature becomes high at non-paper passing part by constituting a heating body of plural laminated heating bodies, providing an overlap part on the different layer of the heating body and independently executing the temperature control of each heating body. CONSTITUTION: At a fixing operation, a brush for energizing 1st and 3rd conductive parts 3, 4 and 7 is controlled by a paper size detector, then, in the case of a small- width paper passes through, the 3rd conductive part 7 is energized so that the heat may be generated only by the 2nd heating body 6, in the case of the large-width paper passes through, the 1st to 3rd conductive parts 3, 4 and 7 are energized so that the heat may be generated by the 1st and 2nd heating bodies 6. Irrespective of the paper size, the temperature distribution on the whole heated surface of the roller is made uniform in such a way, then, the defective fixation caused by that the temperature at the paper passing part becomes lower than that at the non-paper passing part is prevented, and also, the offset caused by that the temperature at the non-paper passing part becomes higher than that at the paper passing part is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat fixing roller provided in a heat fixing device of an image forming apparatus such as an electrophotographic laser printer, a normal copying machine and a plain paper fax machine.

Conventionally, in the heat fixing roller as described above, since the heat of the heating element can be directly utilized,
It is said that the base roll having the heating element mounted on the surface thereof is more advantageous than the base roll having the heating element provided therein. However, such a sheet is not passed because the surface of the heat-fixing roller in the passing portion is absorbed by the paper when the paper having a width smaller than the width of the heat-fixing roller is passed. A temperature difference with the surface of the part is generated.
In this way, if the temperature of the paper being fed decreases and it becomes impossible to supply the amount of heat required for fixing, fixing failure will occur. When a paper having a large width is to be passed, there is a problem that an offset easily occurs on the surface of the heat fixing roller.

[0003]

Therefore, in order to solve such a problem, a fixing device as disclosed in JP-A-4-326387 has been proposed. This is provided on the surface of the base roll by dividing it in the axial direction, heating elements that generate heat by power feeding, temperature detectors that measure the temperature of each heating element, and each heating element independently from the measured temperature and set temperature. It is provided with a temperature controller for controlling the temperature.
In addition, this corresponds to the size of the width of the sheet, and the heating element required for heating the sheet is heated by the power supplied by the temperature controller. However, in such a thing, since each heating element is divided,
There is a problem in that the heat capacity of the adjacent edge portions of the respective heating elements is small and a temperature drop occurs, which may cause fixing failure in the portion of the paper corresponding to this portion.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the problems of the conventional heat fixing roller as described above, and the temperature of the paper passing portion is lowered depending on the width of the paper to cause fixing failure or non-passage. The temperature of the paper portion does not become high and offset does not occur on the surface of the heat fixing roller, and a temperature drop occurs at the adjacent edge of each heating element, which corresponds to this portion. It is an object of the present invention to provide a heat fixing roller that does not cause a fixing failure in a sheet portion.

[0005]

In order to achieve the above-mentioned object, the present invention provides a heat fixing roller having a heating element mounted on the surface of a base roll. Is composed of a plurality of stacked heating elements, and heating elements in different layers have an overlapping portion. The invention described in claim 2 is characterized in that, in the invention described in claim 1, the temperature of each heating element is independently controlled.

[0006]

According to the present invention as described above, at the time of fixing work, a heating element having a width suitable for the width of the paper to be passed is heated to uniformly heat the entire passed paper. In this way, the temperature distribution on all heating surfaces of the roller becomes uniform, regardless of whether the paper is large or small.
The temperature of the paper passing portion is lower than that of the paper non-passing area, causing improper fixing, and the temperature of the paper non-passing portion is higher than that of the paper passing portion and no offset occurs. The adjacent portion of the heating element, which is easy to form, has a large heat capacity due to the formation of the over-wrapper portion, so that the temperature drop in this portion is prevented.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the first embodiment shown in FIG. 1, reference numeral 1 is a base roll having an insulated surface. A pair of first heating elements 2 are provided on the surface of the base roll 1 and the first heat generation is performed. A first conductive portion 3 is provided outside both outer edges of the body 2, a second conductive portion 4 is provided inside both inner edges, and a first insulating portion 5 is provided on the surface of each of the second heat generating portions. The body 6
The third conductive portion 7 is provided on the outside of both outer edges thereof, and the release layer 8 is provided on the surface thereof. The distance between both outer edges of the first heating element 2 is X, the distance between both inner edges thereof is Y, and the second heating element 6 is
If the distance between both outer edges of the sheet is Z, the distance X is wider than the width of the large width paper to be passed, and the distance Z is wider than the width of the small width paper to be passed. The relationship of Z is X>Y> Z, and YZ overlapper portions 9 are formed between both inner edges of the first heating element 2 and both outer edges of the second heating element 6. .

When performing the fixing work by the fixing device using the above-mentioned one, the first, second and third conductive portions 3,
When a brush having a small width is passed through by controlling a brush (not shown) for energizing 4, 7 by a sheet size detecting device (not shown) provided in the fixing device or the image forming apparatus in which the brush is installed, , The second heating element 6 by energizing the third conductive portion 7.
When only a large width of paper is to be passed through, the first, second, third conductive parts 3, 4, 7 are energized and the first, second
The heating element 6 is caused to generate heat, and in this way, regardless of the width of paper of any size, the temperature distribution on the entire heating surface of the roller becomes uniform, and the paper passing portion becomes lower in temperature than the non-paper passing portion. There is no fixing failure, and the non-paper passing portion becomes hotter than the paper passing portion and no offset occurs. Since the over-wrapper portion 9 is formed to increase the heat capacity, the temperature drop in this portion is prevented.

The second embodiment shown in FIG. 2 is a base roll 1
The first heating element 2 provided on the surface of the first heating element 2 is one, and the width of the second heating element 6 provided outside thereof is larger than the width of the first heating element 2, Both outer edges are first
Only the difference from the first embodiment in that the outer wrapper portion 9 is formed to extend outwardly from both outer edges of the heating element 2 and there is no other difference, and the description thereof will be omitted.

In the third embodiment shown in FIG. 3, the width of the first heating element 2 is larger than the width of the second heating element 6, and both outer edges of the first heating element 2 are both outer sides of the second heating element 6. Since the second embodiment is different from the second embodiment in that the overlapper portion is formed to extend outward from the edge and is not different, the description thereof will be omitted.

A fourth embodiment shown in FIG. 4 is a base roll 1
Is a hollow cylindrical body, the first and second heating members 2 and 6 are provided on the inner surface of the base roll 1, and the second insulating portion is provided between the inner peripheral surface of the base roll 1 and the second heating member 6. Since 10 is provided, it is different from the first to third embodiments and there is no other difference, and the description thereof is omitted.

In the second, third and fourth embodiments, if there is a concern that the central portion where the first heating element 2 is stacked with the second heating element 6 is heated, the second heating element 6 is used. The temperature of is controlled to a temperature set so that it does not occur.

[0013]

The present invention is as described above, and the invention according to claim 1 is a heat fixing roller having a heating element mounted on the surface of a base roll, wherein the heating elements are a plurality of laminated heating elements. The heating elements of different layers have overlapping portions, and the temperature of each heating element is controlled independently.Therefore, the temperature of the paper passing portion decreases due to the width of the paper, and fixing failure may occur. , The temperature of the non-sheet passing part does not become high and offset does not occur on the surface of the heat fixing roller, and the temperature drop occurs at the adjacent edge of each heating element. The effect is that there is no fear that fixing failure will occur in the portion of the paper corresponding to.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view of a first embodiment of the present invention.

FIG. 2 is a vertical sectional front view of a second embodiment of the present invention.

FIG. 3 is a vertical sectional front view of a third embodiment of the present invention.

FIG. 4 is a vertical sectional front view of a fourth embodiment of the present invention.

[Explanation of symbols]

 1 Base Roll 2 1st Heating Element 3 1st Conducting Part 4 2nd Conducting Part 5 1st Insulating Part 6 2nd Heating Element 7 3rd Conducting Part 8 Release Layer 9 Overlapper Part 10 2nd Insulating Part

Claims (2)

[Claims] 1. A heat fixing roller having a heating element mounted on the surface of a base roll, wherein the heating element is composed of a plurality of heating elements stacked, and heating elements of different layers have an overlapping portion. Heat fixing roller. 2. The heat fixing roller according to claim 1, wherein the temperature of each heating element is controlled independently.