KR920006988B1 - Heat roll for electro-photography - Google Patents

Abstract

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Description

Heating rolls for electrophotography

1 is a cross-sectional view of a direct heating type heating roll according to one embodiment of the present invention.

2 is a diagram showing a temperature distribution of heating rolls according to Example 1 and a comparative example.

3 is a diagram showing a temperature distribution of a heating roll according to Example 2 and Comparative Example of the present invention.

4 is a diagram showing the temperature rise characteristic based on the difference in the diameter of the core inner diameter and the outer diameter of the high-temperature conductive member of the present invention.

5 is a cross-sectional view showing the structure of a conventional heating roll.

* Explanation of symbols for main parts of the drawings

2: core 3: bonding layer

4: insulation layer 5: resistance layer

6: electrode ring 7: transfer brush

8: insulation layer

The present invention sequentially installs a bonding layer, an insulating layer, a resistive layer, and a surface insulating layer on the outer surface of the core formed in a hollow cylindrical shape, and fixes the toner image on the recording medium by generating heat by energizing the resistive layer. Note relates to the improvement of an electrophotographic heating roll.

A conventionally known heating roll used in an electrophotographic printing system for passionately depositing a toner image transferred onto a recording medium such as copy paper is arranged such that a halogen lamp is installed as a heat source for heating in a hollow cylindrical core. This type of heating roll has the disadvantage that the power consumption is large and the warm-up time required during the start of radiation after energization is long. In addition, there is another disadvantage that the outer diameter can not be reduced because the lamp is installed therein. As a means to solve this disadvantage, a direct-heating heating roll is known in which a heat generating resistor is arranged on the outer surface of the core. 5 is a partial cross-sectional front view showing an example in which an insulating layer 4 and a refracting layer 5 are provided on the outer surface of the core 2 formed in a hollow cylindrical shape through a bonding layer 3. . The electrode rings 6 are respectively fixed to both ends of the resistive layer 5 and electrically connected to the resistive layer 5. The conveying broth 7 is arranged to be in sliding contact with the outside of each electrode ring 6. The surface insulating layer 8 is arranged on the outer circumference of the resistive layer 5 in order to electrically protect the resistive layer 5 and to prevent damage of the resistive layer 5 by external force. Usually, ceramic is used for the insulating layer 8 and the resistive layer 5. If the core is made of an insulating material, the coupling layer 3 and the insulating layer 4 need not be provided.

If ceramic is used for a single insulating layer or resistive layer, it is necessary to use a material close to the thermal expansion coefficient of the ceramic (usually 5 to 10 × 10 ⁻⁶ / ° C.) for the material of the core. If an aluminum alloy having a large coefficient of thermal expansion is used as a core, cracking occurs in the ceramic due to repetition of the thermal load generated during manufacture or use, and as a result, the electrical properties decrease and the resistor is disconnected. In view of economics, iron alloys (mild steel, ferritic-based stainless steel, or martensitic-based stainless steel) are most preferred. In addition, an insulating ceramic such as alumina may be used.

However, when using iron alloy, alumina, etc., the coefficient of thermal expansion is smaller than that of aluminum, steel, and their alloys, so that the temperature of each part of the roll becomes uneven, causing fixing failure and raising the temperature of a specific part to high temperature. There are disadvantages.

It is therefore an object of the present invention to provide an electrophotographic heating roll which can alleviate the effects caused by the difference in thermal expansion coefficient and promote the rise of the temperature of the heating roll to a predetermined temperature to solve the above disadvantages by the prior art.

For this purpose, in the present invention, a bonding layer, an insulating layer, a resistance layer, a surface insulating layer, and the like are sequentially provided on the outer surface of the hollow cylindrical core, and bearing members suitable for bearings are fixed to both ends of the heating roll. An electrophotographic heating roll having a heat generating resistor is provided. Inside the core are pipes or round bars made of aluminum, aluminum alloys, copper, copper alloys, etc., having a thermal conductivity greater than that of mild steel.

In the present invention, it is preferable to provide a gap of 0.2 mm or more between the inner surface of the core and the outer surface of the member made of the high-temperature conductive material to alleviate the effect due to the difference in the coefficient of thermal expansion during temperature rise. It is also desirable to configure in a manner that practically prevents axial movement of the pipe or the round rod. The above structure has the effect of preventing peeling of the insulating film, the resistive film and the like. Moreover, in this invention, since it has a high temperature conductive material in the inside of a heating roll, there exists an advantage that temperature becomes uniform. Providing a gap of 0.2 mm or more also promotes a rise in temperature to a predetermined temperature of the heating roll as compared to the case where a smaller gap is provided.

1 is a cross-sectional view of a heating roll according to the present invention. In this figure the pipe 1 is made of a high temperature conductive material such as aluminum and has a thickness of 2-3 mm. However, the material may be made of aluminum alloy, copper, copper alloy and the like. If necessary, a round rod may be used instead of the pipe (1). The core 2 of mild steel is formed into a hollow cylindrical shape, and a gap of 0.2 mm or more is provided between the core 2 and the pipe 1.

On the outer surface of the core, a bonding layer 3 made of nickel-aluminum-molybdenum (Ni-Al-Mo) having a thickness of 25 μm, an insulating layer 4 made of aluminum oxide (Al ₂ O ₃ ) having a thickness of 30 μm, and thickness A resistive layer 5 as a heat generating resistor made of aluminum oxide + nickel chromium (Al ₂ O ₃ + NiCr) having a thickness of 70 μm, and an insulating layer 8 as an insulating film made of aluminum oxide (Al ₂ O ₃ ) having a thickness of 100 μm. This is covered sequentially. On both ends of the resistive layer 5, an electrode ring 6 made of a conductive material such as aluminum bronze is provided protrudingly, and the transfer brush 7 is also provided slidingly. Moreover, the outer peripheral surface of the surface insulating layer 8 is coat | covered with Teflon about 30 micrometers in thickness, and the end surface of the insulating layer 4 in the electrode ring 6 back side is insulated with silicone resin. According to the said structure, when a heating current is supplied from the transfer brush 7 to the resistance side 5 via the electrode ring 6, a heating roll exhibits the function.

Example 1

An aluminum (A5056) pipe having an outer diameter of 36.4 mm, an inner diameter of 33.8 mm, and a length of 350 mm on the inner surface of a conventional heating roll using an mild steel core with an outer diameter of 40 mm, an inner diameter of 37.2 mm, and a distance between electrodes of 330 mm. Is provided in a manner that actually corresponds to the distance between the electrodes. In this example, the temperature distribution of the conventional structure without the pipe was compared. The result is shown in FIG. The dotted line in the figure shows the temperature distribution when the temperature of the heating roll according to the present invention is stabilized and immediately after passing 100 sheets of A4 paper continuously.

On the other hand, the solid line shows the temperature distribution in the conventional heating roll without the high temperature conductive material. As apparent from the drawings, the present invention exhibits its ability to greatly improve the temperature distribution and to improve the fixing performance.

Example 2

On the inner surface of a conventional heating roll using a mild steel core having an outer diameter of 15 mm, an inner diameter of 12.6 mm, and an electrode distance of 220 mm, the outer diameter is 11.8 mm and corresponds to the distance between round bar electrodes made of aluminum (A5056). Installed in such a way. In this example, the temperature distribution of the conventional structure without the round bar was compared. The result is shown in FIG. The dotted line in the figure shows the temperature distribution when the temperature of the heating roll according to the present invention is stabilized and immediately after passing 100 sheets of A4 paper continuously. On the other hand, the solid line shows the temperature distribution in the conventional heating roll without the high temperature conductive material. As is evident from the figure, the present invention makes it possible to improve the temperature distribution.

Example 3

On the inner surface of a conventional heating roll having an outer diameter of 20.0 mm, an inner diameter of 17.0 mm, and an electrode-to-electrode distance of 220 mm, an outer diameter of 16.8 mm and a round bar made of aluminum alloy A505 correspond to the distance between the electrodes. It was installed and the test was conducted in the same manner as in Example 2. Thus, the result was obtained similarly as in Example 2.

Example 4

The temperature rise characteristic to 190 degreeC was investigated by changing the diameter difference between the inner surface of a roll and the outer surface of a high-temperature conductive material to 0.2 mm and 0.8 mm in the heating rolls of Examples 1, 2, and 3. The result is shown in FIG.

As evident in the figure, heating rolls with a diameter difference of 0.8 mm show shorter rise times compared to heating rolls with a diameter difference of 0.2 mm. In particular, in the case where the roll diameter is 200 mm or less and the rise time is about 40 seconds or less, the temperature distribution is good and the rise time is short, thereby showing good results.

A method of installing the high temperature conductive material by providing a gap as described above as well as a means of installing a high temperature conductive material on the inner surface of a conventional heating roll, a method of attaching the high temperature conductive material using an inner flame spray gun, a large gap And a method of using solder, an adhesive or the like in this gap, or a method of performing shrinkage fixation or expansion fixation.

Among the above methods, the method of installing a high temperature conductive material by providing a gap is the simplest, and this method is very preferable because the stress generated in the outer cylinder during heating is small.

It goes without saying that the inner high temperature conductive material also extends to the end of the roll, and that a composite pipe can be used.

Claims (1)

A surface heating electrophotographic heating roll having a heat generating resistor 5 on the outer surface of a hollow cylindrical core 2 made of mild steel, wherein the heating roll is formed in a pipe shape and inserted into the core. An electrophotographic heating rule comprising a metal material which is aluminum.

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