JPH06348177A - Fixing roller for electrophotography - Google Patents

Abstract

PURPOSE:To enable temperature control and maintain uniform temperature distribution by forming the inner diameter of a linear heat pipe larger than that of a heat radiation part, and providing a releasing layer around the heat radiation part. CONSTITUTION:The inner diameter of a heating part 1b of a linear heat pipe is formed larger than that of a heat radiation part 1a, and a releasing layer is installed around the heat radiation part 1a. The material of the heat pipe which constitutes a fixing roller is desirably copper or phosphor bronze. Though the inner diameter of the heating part 1b must be larger than that of the heat radiation part 1a, if it is too large, the amount of working liquid must be increased and, if it is too small, it exerts less effect. The fixing roller 1 thus constructed allows the working liquid to be accumulated easily at the heat radiation part 1b and, therefore, even if the heating part side of the fixing device is higher than the horizontal, the interior of the heating part 1b is not dried out and also the temperature control is not brought into inoperative condition.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing roll for a printer, a fax machine, a copying machine, etc. using an electrophotographic process.

[0001]

2. Description of the Related Art Conventionally, a heating roll system has been generally used as a fixing device for electrophotography. This type of fixing device heats the fixing roll by providing a heat source such as a halogen lamp in a cylindrical fixing roll having a release layer on the surface and applies pressure between the fixing roll and the pressure roll. While being rotated, the copy image is fixed by fusing the toner through a sheet carrying the powder toner image between the fixing roll and the pressure roll.

However, in a fixing device using a fixing roll having such a halogen lamp, maintenance work such as the need to pull out the halogen lamp when replacing the fixing roll is involved, and the halogen lamp has a small diameter. Since there is a limit to downsizing, it is impossible to downsize the fixing roll, and thus there is a limit to downsizing the fixing device.

On the other hand, as a means for solving the above problems, instead of heating the entire fixing roll by passing a halogen lamp through the fixing roll, a heat pipe is embedded in the fixing roll or heat is applied. A technique has been proposed in which a release layer is provided around the heat radiating portion of the pipe to form a fixing roll, and a heating portion provided at the end of the fixing roll is heated to heat the entire roll to a uniform temperature.

[0004]

However, when a machine incorporating the above-mentioned end-heating type fixing device using a heat pipe is placed in a non-horizontal installation place, the heating unit side of the fixing device is in a horizontal position. When the temperature becomes higher, the working liquid in the heat pipe is unevenly distributed, and the heating portion side is drained to be in a dry-out state, which causes a problem that the temperature control of the fixing roll becomes impossible. Therefore, the present invention provides a fixing roll capable of controlling the temperature and maintaining a uniform temperature distribution even when the heating unit side of the fixing device placed at a non-horizontal installation position is higher than the horizontal position. Aimed at.

[0005]

In order to achieve the above-mentioned object, in the present invention, the inner diameter of the heating portion of a straight pipe-shaped heat pipe is formed larger than the inner diameter of the heat radiating portion, and the heat radiating portion is separated from the heat radiating portion. A mold layer was provided to form a fixing roll for electrophotography.

Copper or phosphor bronze is preferable as the material of the heat pipe constituting the fixing roll of the present invention. Water or alcohol can be used as the working fluid of the heat pipe, but if the amount of such working fluid is too small, the temperature distribution is not uniform enough, and if it is too large, it takes time for the working fluid to warm up. It's too practical to use,
20-40% of the internal volume of the fixing roll is preferable.

The inner diameter of the heat radiating portion needs to be larger than that of the heat radiating portion. However, if the inner diameter of the heat radiating portion is too large, the amount of the working fluid must be increased. More preferably, the size is about 10 to 50%. The release layer provided around the heat radiating portion of the heat pipe may be formed by coating, adhering, or adhering fluororesin or silicone rubber, or formed by fitting a tube. But good.

[0008]

In the fixing roll having the above-mentioned structure, the working liquid is likely to be accumulated in the heating portion, so that the inside of the heating portion is in the dry-out state even if the heating portion side of the fixing device is higher than the horizontal position. There is no possibility that temperature control will be disabled.

[0009]

1 shows a fixing device of a copying machine, 1 is a fixing roll, 2 is a pressure roll, 3 is a heating source, 4 is a heating part cover, 5 is a thermistor of temperature control means, and 6 is a reflecting plate. is there. The fixing roll 1 of the present invention has a total length of 345 mm, an outer diameter of the heat radiating portion 1a is 15.5 mm, and a length of the heating portion 1b is 55 mm.
It is composed of a copper heat pipe with an outer diameter of 17.2 mm and a thickness of 0.9 mm. The heat radiating portion 1a has an inner diameter of 13.6 mm, the heating portion 1b has an inner diameter of 15.4 mm, and the hydraulic fluid 1c is used. As a result, 35% of the internal volume of water is contained. Both ends of the heat dissipation part are a support shaft part and a drive gear attachment part, and a part of the 220 mm long paper passing surface sandwiched between the two support shaft parts is covered with a PFA tube with a thickness of 50 μm. , A release layer.

The pressure roll 2 is made of an iron 8 mm core bar coated with a 4 mm thick silicone sponge, and the sponge layer has an ASKER C hardness of 36 °.
Is. A 250 W halogen lamp is used as the heating source 3, and the reflecting plate 6 is provided to increase the heating efficiency of the fixing roll. The thermistor 5 is for detecting the surface temperature of the fixing roll 1 and controlling the temperature of the fixing roll 1.

When the fixing device as shown in FIG. 1 is installed and operated at an inclined position such that it is horizontal, -3 °, and + 3 ° with respect to the heating unit side, a predetermined set temperature, that is, 160 It was examined how the temperature distribution of the fixing roll, which was controlled so as to be ℃, changed, and the results are shown in Table 1. The surface temperature of the fixing roll was measured at three points A, B and C in FIG.

For comparison, the fixing roll 1 of the present invention is also used.
The temperature distribution of the fixing roll was measured in exactly the same manner as above for the fixing device of FIG. 2 which is exactly the same as the fixing device of FIG. 1 except that a conventional heat pipe type fixing roll was incorporated instead of The results are also shown in Table 1.

The fixing roll 1'of the comparative example used here is used.
Has a total length of 345 mm, an outer diameter of 15.5 mm, and a thickness of 0.9.
mm straight tubular copper heat pipe, which is exactly the same as the fixing roll 1 of the present invention, except that one end portion having a length of 55 mm serves as a heating portion and the other portion serves as a heat radiating portion. It has a structure.

[0014]

[Table 1]

As can be seen from Table 1, the fixing roll of the present invention operates normally without losing the working fluid on the heating side even when tilted by + 3 °, and the temperature difference due to the tilt of the fixing device did not occur. On the other hand, in the conventional straight tube-shaped fixing roll, a temperature difference did not occur under the condition of horizontal and -3 ° inclination with respect to the heating section side, but only + A temperature increased at + 3 ° inclination. As a result, the temperatures of B and C did not follow each other, and it became impossible to control the temperature of the fixing roll by the thermistor. This indicates that the hydraulic fluid has run out and is in a dry-out state, as shown in FIG.

[0016]

EFFECTS OF THE INVENTION In an end heating type fixing device using a heat pipe as a fixing roll, by using the fixing roll of the present invention, even if the fixing device is installed at a tilted position, a dry-out state occurs in the heat pipe. Therefore, it is possible to surely avoid the risk that the temperature of the fixing roll cannot be controlled.

[Brief description of drawings]

FIG. 1 is a sectional view of a fixing device using a fixing roll of the present invention.

FIG. 2 is a cross-sectional view of a fixing device using a conventional fixing roll, which is tilted by + 3 °.

[Explanation of symbols]

 1 Fixing Roll 1a of the Present Invention 1a Heat Dissipation Part 1b Heating Part 1c Hydraulic Fluid 1'Conventional Fixing Roll 2 Pressure Roll 3 Heating Source 4 Heating Part Cover 5 Thermistor 6 Reflector

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masakuni Shimoyama 5-11-3 Shimbashi, Minato-ku, Tokyo Sumitomo Light Metal Industry Co., Ltd.

Claims (1)

[Claims] 1. A fixing roll for electrophotography, characterized in that an inner diameter of a heating portion of a straight tubular heat pipe is formed larger than an inner diameter of a heat radiating portion, and a release layer is provided around the heat radiating portion.