JP2997434B2 - Rotating body for fixing - Google Patents

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 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. 58-3).
No. 8156). 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 life is 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.

[Means for Solving the Problems]

According to the present invention, there is provided a fixing rotator for fixing a toner image on a sheet, wherein the fixing rotator has an axial length in the axial direction. A core bar set shorter than the core bar, and both ends fixed to both ends of the core bar and made of a material having a lower thermal conductivity than the core bar. The problem is solved by providing a hole for burying the heat pipe, and burying both ends of the heat pipe projecting from the metal core in the both ends.

[0009]

In the present invention, since both ends of the fixing roller are made of a material having a low thermal conductivity, heat can be prevented from escaping through bearings and gears. Further, since the heat pipe penetrates the entire length of the cored bar in the longitudinal direction, it is possible to surely set a portion where the temperature change is sharp to a uniform temperature. Furthermore, if the heat pipe is shorter than the hole for burying, the positioning of the heat pipe becomes difficult. However, in the present invention, the heat pipe can be easily attached to the core during assembly of the heat pipe.

[0010]

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 comprises a metal 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 metal core 3, and a thermistor is provided. 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 FIG. 2, the fixing roller 11 is provided with flanges 9a and 9b made of, for example, resin and having low heat conductivity fixed to both ends of the core 3 having good heat conductivity. The heat pipe 18 is longer than the paper passing area L. The fixing roller 11 is provided with the flange 9.
a, 9b through the bearings 10a, 10b provided on the side plate 12
a, 12b so as to be rotatable, and driven to rotate by a driving unit via a gear 13.

As described above, since the flanges 9a and 9b having poor heat conductivity are arranged at both ends of the cored bar 3, the bearing 1
The heat is prevented from escaping from the gears 0a, 10b and the gear 13, and the paper passing area L is kept sufficiently warm. In this case, the temperature difference in the fixing roller 11 is reduced by the heat pipe 18 having a good heat transfer effect, and the temperature uniformity is maintained.

[0013]

According to the first aspect of the present invention, the heat insulating properties at both ends of the fixing rotating body are improved, and the heat of the heater is hardly transmitted to the side plates and the driving gears. As a result, power consumption is reduced, the rise time is shortened, Features such as simplification of the configuration are achieved because there is no need for an insulating bush. Furthermore, since the heat pipe penetrates in the entire longitudinal direction of the cored bar,
It is possible to ensure a uniform temperature in a portion where the temperature changes drastically, and it is easy to attach the heat pipe to the core during assembly of the heat pipe.

[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]

 Reference Signs List 1,11 Fixing roller 2 Pressure roller 3 Core 6 Heater 18 Heat pipe 9a, 9b Low thermal conductivity material L Paper passing area

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Jun Okamoto 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Hiroshi Yokoyama 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Yutaka Fukuchi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) References JP-A-60-55368 (JP, A) JP-A-54- 34839 (JP, A) JP-A-53-66744 (JP, A) JP-A-58-38165 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/20

Claims (1)

(57) [Claims] 1. A fixing rotator incorporating at least one heat pipe and fixing a toner image on paper, wherein a fixing rotator has an axial length shorter than the heat pipe. A metal part and both ends fixed to both ends of the metal core part and made of a material having a lower thermal conductivity than the metal core part, and a hole for burying a heat pipe in the metal core part. A fixing rotator, wherein both ends of the heat pipe protruding from the cored bar are embedded in the both ends.