JPH11338305A - Fixing rotary body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformize the surface temperature of the fixing roller and the pressure roller of a fixing device in an axial direction and to attain electric power saving. SOLUTION: The core bar part 3 of a fixing rotary body 1 incorporating a heater 6 and at least one heat pipe 8 is provided with a hole for embedding the heat pipe. Then, the length of the heat pipe 8 of the fixing rotary body 1 in the axial direction and the length of the heat generating part of the heater 6 are set to be shorter than the length L of the paper-passing area of the fixing rotary body 1 and also to be within a maximum paper-passing area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing rotator incorporating a heater and at least one heat pipe for fixing a toner image on paper.

[0002]

2. Description of the Related Art Generally, in a fixing device of an image forming apparatus such as an electronic copying machine, a printer, a facsimile, etc., fixing is performed by coating a resin such as PTFE on a cored bar and providing a heater inside the cored bar. Roller and this fixing roller
Using a pressure roller provided with a mechanism pressed by a roller, fixing is performed by passing a transfer sheet carrying a toner image through a nip formed between the rollers. The pressure roller usually has a surface layer made of an elastic material such as silicon rubber so that the nip portion can be easily formed.

It is desirable that the fixing roller and the pressure roller have uniform temperatures in the axial direction. When the temperature becomes non-uniform, wrinkles, unfixed portions, offsets, and the like occur on the transfer paper due to a nip difference based on a difference in thermal expansion between portions having different temperatures.

For this reason, it has been well known that a heat pipe is built in a fixing roller to make its surface temperature uniform in the axial direction of the fixing roller (for example, see Japanese Utility Model Application Laid-Open No. 58-158).
38156 gazette). The heat pipe makes the temperature uniform by exchanging heat of vaporization and latent heat when the working fluid vaporizes and liquefies inside the heat pipe.

[0005]

The heat pipe used for the fixing roller and the pressure roller of the fixing device is to make the surface temperature of each roller uniform in the roller axis direction. When each roller is heated from a cold state, the heat easily escapes from a portion where the fixing roller having a built-in heater is in contact, for example, a bearing or a driving gear, so that the heat efficiency is deteriorated and the fixing roller is heated. The temperature at the end of the
As a result, the occurrence of defective fixing was inevitable. On the other hand, as shown in FIG. 3, a heat insulating bush 13 is provided between the bearing 10b provided on the side plate 12b and the fixing roller 1.
Is used, but the shape is inevitably complicated.

Further, when the fixing device is heated and is in a stable state, if continuous transfer of small-size transfer paper is performed, a temperature difference is generated between the paper passing portion and the non-paper passing portion of the roller, If the temperature of the non-sheet passing portion at the end of the roller rises and the large size transfer paper is passed immediately after the continuous passing of the small size paper, fixing failure due to low temperature in the sheet passing portion of the small size paper may occur. However, inconveniences such as occurrence of offset due to high temperature of the non-sheet passing portion occurred. When such a temperature rise at the end of the roller is repeated, the fixing roller and the pressure roller are deteriorated, and it is inevitable that their service lives are shortened. Furthermore, since heat pipes are expensive, the use of uselessly long heat pipes results in a significant increase in cost and impairs the usefulness of heat pipes, and the heaters use conventional heat pipes without heat pipes. Therefore, the power consumption of the heater has not been reduced yet.

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned disadvantages by making the surface temperature of the fixing roller and the pressure roller of the fixing device uniform in the axial direction.

[0008]

According to the present invention, there is provided a fixing rotator for fixing a toner image on paper, comprising a heater and at least one heat pipe. A hole for burying a heat pipe is provided in the metal part, and the length of the heat pipe and the length of the heating part of the heater in the axial direction of the rotator for fixing are determined by the paper passing area of the rotator for fixing. And is within the maximum paper passing area.

Further, in order to solve the above-mentioned problems, the present invention proposes, in the above-described configuration, a length of a heating portion of a heater in an axial direction of the fixing rotating body is shorter than a length of a heat pipe. I do.

[0010]

According to the first aspect of the invention, the length of the heat pipe in the axial direction of the fixing rotating body and the length of the heat generating portion of the heater are smaller than the length of the paper passing area of the rotating body, and the maximum paper passing area. Because there is no need to use a long heat pipe and a long heater heating section, it is possible to prevent abnormal temperature rise at the end of the fixing roller.

According to the second aspect of the present invention, since the length of the heater is appropriately shorter than that of the heat pipe, power can be saved.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the fixing device shown in FIG.
And the pressure roller 2 are arranged so as to be pressed against each other.
The fixing roller 1 includes a core 3 and a surface release layer 4 such as Teflon. As shown in FIG. 2, a heater 6 is provided in a central hole 5 in the axial direction of the core 3 and a thermistor. 7, the surface temperature of the fixing roller 1 is detected, and the heater 6 is turned on so that the surface temperature becomes constant (for example, 158 to 170 ° C.)
Turn off to control. Further, a plurality of heat pipes 8 are built in the cored bar 3, and these heat pipes 8 are arranged in parallel with the axis of the fixing roller 1.
The core 3 is made of an extruded material. At this time, since the heat pipe 8 is parallel to the axis of the fixing roller 2, the hole for inserting the heat pipe 8 can be formed at the same time.

In the fixing roller 1 shown in FIG. 2, the heat pipe 8 is disposed in the axial direction of the fixing roller 1, and the length of the heat pipe is set shorter than the length of the maximum sheet passing area L. I have. This is because even if the length of the heat pipe is shorter than the maximum paper passing area L, due to its extremely high thermal fluidity,
Since the surface temperature of the fixing roller in the paper passing area can be maintained in an appropriate and uniform range, it is not necessary to use an unnecessary long heat pipe.

The length of the heat generating portion 6a of the heater 6 is as follows:
In the axial direction of the fixing roller 1, the length is set to be shorter than the maximum sheet passing area L. This is because even if the length of the heat generating portion 6a is shorter than the maximum paper passing area L, the action of the heat pipe causes
Since the surface temperature of the fixing roller in the paper passing area can be maintained in an appropriate and uniform range, the power consumption of the heater can be reduced.

Further, the length of the heat generating portion 6 a of the heater 6 is set shorter than the heat pipe 8 in the axial direction of the fixing roller 1. This is because even if the length of the heat generating portion 6a is shorter than the heat pipe 8, the surface temperature of the fixing roller in the paper passing area can be maintained in an appropriate and uniform range due to the extremely high thermal fluidity of the heat pipe. Power consumption can be reduced.

[0016]

According to the present invention, it is not necessary to use an unnecessarily long heat pipe, and the surface temperature of the fixing roller in the paper passing area can always be maintained in an appropriate and uniform range. further,
Reduction of the power of the heater and prevention of abnormal temperature rise in the non-sheet passing portion of the fixing roller when the small-size transfer paper is continuously passed, thus extending the life of the fixing roller and the pressure roller. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a fixing device to which the present invention is applied.

FIG. 2 is a longitudinal sectional view of the fixing roller shown in FIG.

FIG. 3 is a partial cross-sectional view showing a conventional heat insulating support mechanism of a fixing roller.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixing roller 2 Pressure roller 3 Core metal part 6 Heater 6a Heating part of heater 8 Heat pipe L Paper passing area

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Jun Okamoto 1-3-6 Nakamagome, Ota-ku, Tokyo Stock inside Ricoh Company (72) Inventor Hiroshi Yokoyama 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Inside Ricoh Company (72) Inventor Yutaka Fukuchi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company

Claims (2)

[Claims] 1. A fixing rotator for fixing a toner image on paper, wherein the fixing member has a heater and at least one heat pipe therein, and a hole for burying a heat pipe is provided in a core of the rotator. The length of the heat pipe in the axial direction of the fixing rotator and the length of the heat generating portion of the heater are shorter than the length of the sheet passing area of the fixing rotator and within the maximum sheet passing area. A rotating body for fixing characterized by the following. 2. The fixing device according to claim 1, wherein a length of a heating portion of the heater in an axial direction of the fixing rotating body is shorter than a length of the heat pipe.