JPS60118868A - Heat fixing device - Google Patents

Abstract

PURPOSE:To reduce electric power consumption and to improve mechanical strength by embedding a conductive ceramic layer consisting essentially of a material which generates heat when electricity is conducted thereto to the inside of a core body made of ceramics consisting essentially of alumina near the surface thereof in the state of sand wiching said layer. CONSTITUTION:The core body of a heat roll 10 is constituted of ceramics consisting essentially of aluminal formed into a circular cylindrical shape. An antioffset layer 11 consisting of a material having good release characteristic and heat resistance is provided on the circumferential surface of the roll 10 and a conductive ceramic layer 12 consisting essentially of titanium oxide which is a conductive material to generate heat when electricity is conducted thereto is embedded near the circumferential surface in the core body. The layer 12 is sandwiched by the ceramic layer consisting essentially of the alumina of the core body. End plates 13 constituted of the ceramics having the same essential component as the layer 12 and provided with fulcrum shafts 13a for supporting the roll are integrally formed at both ends of the roll 10. When the shafts 13a contact with power source terminals provided with bearings having heat resistance and insulation characteristic, electric power is supplied, by which the electric power consumption is decreased and the mechanical strength is improved.

Description

[Detailed description of the invention] (Technical field) The present invention relates to a heat fixing device.

(Prior art) Currently, the fixing devices commonly used in copying machines include pressure fixing, heat roll fixing, atmosphere fixing, and Furanono single type? Examples include devices using radiant heat fixing, hot plate fixing, and the like. Among these various electrolytic layer devices, from the viewpoint of safety and thermal efficiency, those using thermal roll fixing are mainstream. In addition, with respect to wet-type copying machines, if, for example, a heat fixing roll comes into contact with the surface of image 1, image II will be disturbed, so that only non-contact types such as hot plate fixing can be used.

On the other hand, various types of thermal roll fixing devices are used, such as those with large or small thermal rolls, and those with different rotational speeds. With such a hot roll fixing device, for example, if you are a copying machine user who only makes one copy per month, you may want to turn on the power only when copying rather than leaving it on. This is extremely common, and for this reason, it is required to immediately raise the fixing temperature when the power is turned on.

Regarding the power supply, since the higher the copying speed, the higher the power consumption, it is currently necessary to use a power supply with a voltage of 200 V, which is higher than the general voltage.

However, as mentioned above, the power supply voltage is 10
In order to improve the copying speed while using such a general power supply, it is necessary to shorten the rise time of the fixing temperature as much as possible. It is necessary to further improve the thermal efficiency of the roll.

By the way, regarding the above-mentioned rise time, this time is 0 seconds for flap fixing and pressure fixing, and 20 seconds for hot roll fixing.
The average time is about 20 minutes. In such heat roll fixing, when it is desired to shorten the rise time of the fixing temperature as much as possible, this function can be used, for example, by reducing the weight of the core bar 2 of the fixing roll 1, as in the conventional example shown in Figure 1. This can be achieved by increasing the power input to the internal heater, but for example, by reducing the number of roll core wheels and reducing the roll diameter from 6f,
The core metal thickness must also be made as thin as possible; in this way, if the pressure applied to the upper and lower rolls becomes large, the rolls will become stale, resulting in poor fixing.
This may even lead to plastic deformation of the fixing roll.

In order to solve the various problems mentioned above, heating elements using ceramics have recently been proposed. Due to this characteristic, such ceramics have excellent strength, and therefore can sufficiently cope with a relatively large pressing force. However, each of the conventional proposals using such ceramics has a complicated structure and is expensive, and the rising efficiency of the fixing temperature is not very good, making it difficult to use it well in fixing devices. I was in a situation where I couldn't do it.

For example, in the field of ceramic heating elements, Japanese Patent Application Laid-Open No. 54-3084 published a heating element by printing a heating pattern on ceramic.
1 and Japanese Patent Application Laid-open No. 109379/1989 in which the heating element is held between ceramics, these examples do not allow the same degree of external shape of the roll. Otherwise, the heating element is made of a metal or a metal compound, which has a different coefficient of thermal expansion than ceramic, which has the disadvantage that the heating element may peel or break. Furthermore, regarding thermal efficiency, since heat is taken away from the heating element to the ceramic, the contribution of heat to fixing is reduced, and the rising speed of the fixing temperature cannot be made very fast.

(Objective) It is an object of the present invention to provide a heat fixing device that is inexpensive, has excellent strength, has good temperature rise characteristics, and has good thermal efficiency, which has been designed in consideration of the above-mentioned problems.

(Structure) The present invention is characterized in that the core body constituting the heating section side is formed of ceramic, and a conductive ceramic layer as a heating element is interposed within the core body.

Hereinafter, the present invention will be explained with reference to an actual case of cough shown in the drawings.

・Figure 2 shows the heating section (l) using a heat roll.
-i is shown.

In the same example 1, the heat roll 1U has a core made of ceramic mainly made of alumina and having a cylindrical shape.
1jt I)y is being done.

On the circumferential surface of the Nb roll 10, an offset prevention layer 11 made of a material with good mold releasability and heat resistance, such as fluororesin or fluororesin, is provided.

On the other hand, a conductive ceramic layer 12 mainly composed of titanium oxide, which is a conductive material that generates heat when electricity is applied, is buried near the circumferential surface inside the core of the thermo roll. 12 are sandwiched between the alumina-based ceramic layers of the core.

End plates 16 made of ceramic having the same main component as the conductive ceramic layer 12 and provided with roll support textures 13a are integrally formed at both ends of the heat roll 1U.

This end plate 16 is in contact with the conductive ceramic layer 12, and the supports 11111113a supply power to the conductive ceramic layer 12 by coming into contact with a power terminal provided on a 100-degree thermal insulation bearing (not shown). Let's do it.

Therefore, the conductive ceramic layer 12 generates heat when placed in a solid state with an external power source.

By the way, the present inventor has discovered that for such a heat roll,
I calculated the time it took for the peripheral surface temperature to reach 2000°C, which corresponds to the fixing temperature, and found the following (1).

Conductive ceramic layer 12 of the core of the roll 10
Diameter D1 up to 65mm, conductive ceramic layer 120
The thickness t is 1 arm, and the outer diameter D2 of the core of the roll 10 is 4.
0 order, and the conductive ceramic layer 12 has a resistance value of 4 [J °C and a specific resistance of 26 Ω·clrL, and when a voltage of 100 V is applied from the power supply terminal, an average power of soUw is applied to the heat roll itself. was obtained, and the time required for the surface height of the roll to reach from 5°C to 20°C was 10 seconds.

In addition, the thickness of the conductive ceramic layer 12 is t, 8
mm, it took 17 seconds to reach the surface temperature of 200°C.

This rise time can be said to be extremely short since a heat roll made only of conductive ceramics takes about 5 U seconds.Also, even when compared in terms of thermal efficiency, the heat per heat roll of the actual case mentioned above is quite short. The numerical value is 0.98, and considering that the roll using a conventional ceramic heating element or a general metal core heating element has a value of about 0.8, the thermal resistance of the above-mentioned sister example is It was confirmed that rolls achieved a significant improvement in thermal efficiency.

Further, the heating member in the present invention is not limited to the roll-shaped one described above, but may also be a plate-shaped one.

That is, in Fig. 6, the hot plate 20 is made of ceramic mainly composed of alumina, and the offset prevention layer 21 is provided on its surface, and the inside i near the surface of the hot plate 20 (similar to that shown in Fig. 2) The so-called conductive ceramic II1122 whose main component is titanium oxide is buried.
This conductive ceramic layer 22 is sandwiched between the ceramic layers of the hot plate 20 mainly composed of alumina.

In the hot plate 20 in this state, the conductive ceramic layer 22
A terminal (not shown) is connected to the conductive ceramic layer 220 to promote heat generation.

(Efficacy) According to the present invention, extremely high thermal efficiency can be achieved and the temperature rise time can be shortened, so power consumption can be reduced and the heating member has excellent strength. It is possible to obtain an effect that a fixing device having the above-mentioned structure can be made cheaper than one made only of four-electrode ceramics, for example.

[BRIEF DESCRIPTION OF THE DRAWINGS] ・Figure 1 is a perspective view showing a conventional example of a heating member, Figure 2 is a cross-sectional view of the main part showing a sister example of the present invention, and Figure 6 is another example of a sister example of the present invention. 1.10.20 Heating member and heating roll and hot plate 12.22 Conductive ceramic layer

Claims (1)

[Claims] A conductive ceramic layer whose main component is a material that generates heat when electricity is applied is embedded near the inner surface of the core body made of ceramic whose main component is alumina. A heating fixing device configured in a sandwiched state and having a heating section (A) connected to a power source to the conductive ceramic layer.