JPH0469791B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention provides a facsimile machine using electrophotography;
The present invention relates to a heat fixing roller used in image forming apparatuses such as printers and copying machines.

Conventionally, recording paper with a toner image formed on its surface is inserted between a heat fixing roller and a pressure roller that are placed in parallel and in pressure contact with each other.
A heat fixing device that heats and melts the toner and fixes the toner image on a recording paper is well known, and as a heat fixing roller used in such a device, a tubular heat generating heater is inserted and installed in the internal space of a hollow roller core. There is a device in which the roller core is heated by radiant heat from a heater.

However, in a heat fixing roller having such a configuration, it takes a considerable amount of time to preheat the roller core surface to reach the temperature required for fixing the toner image, and the temperature distribution is uniform due to heat loss from both ends of the roller core. It has the disadvantage that it cannot be obtained.

For this reason, a conventionally known heat fixing roller has been proposed in which a heat-resistant heat-generating conductor is wound or buried around the outer peripheral surface of a roller core made of ceramic material, and the roller core itself is directly heated. (Japanese Patent Application Laid-Open No. 54-30841, JP-A No. 56-
138766), it is impossible to arrange the heat generating conductor on the outer circumferential surface of the roller core without any gaps even in the heat fixing roller having such a structure, and the temperature in the part where the heat generating conductor is buried and the other circumferential surface part is low. Not only is there a risk of variations in distribution, but also because the heating conductor is wrapped around the outer circumferential surface of the roller core or buried very close to the outer circumferential surface, heat can easily escape from the outer circumferential surface. , has the disadvantage of poor heat storage effect.

In order to prevent such drawbacks, the applicant first formed the roller core body itself from a resistor having positive temperature characteristics such as barium titanate porcelain (hereinafter referred to as PTC), and made the resistor itself generate heat. (Japanese Patent Application Laid-Open No. 57-73772)
However, forming the roller core body itself from such a resistor leads to an increase in cost and weight even if it is made into a hollow structure, and furthermore, the entire resistor, which is formed in such a dense manner, cannot be used as a toner image. In order to generate heat to the temperature required for fixing, a considerable amount of preheating time is required, although not as long as in the first prior art.

In view of the shortcomings of the prior art, the present invention provides a heating fixing roller with a heat storage effect, thereby achieving uniform temperature distribution on the outer peripheral surface of the roller, preventing heat loss from the outer peripheral surface, and reducing power consumption. It is an object of the present invention to provide a heating fixing roller that can reduce the amount of heat.

In addition, the present invention particularly provides a roller core made of PTC or other ceramic resistive material, which is configured to generate heat. An object of the present invention is to provide a heat fixing roller that can reduce heat generation capacity and shorten preheating time.

The first aspect of the present invention is characterized in that the heat fixing roller has a honeycomb structure and positive temperature characteristics, and has a heating element inside and performs heat fixing while bringing an unfixed toner image into contact with its outer peripheral surface. An offset prevention layer is coated on the outer peripheral surface of a ceramic roller made of a ceramic resistor.

Further, the second invention is characterized in that the outer circumferential surface of the ceramic crawler core has a heating conductor formed on the outer circumferential surface.
An offset prevention layer is coated on the outer peripheral surface of a ceramic crawler having a two-layer structure formed by integrally wrapping a ceramic sheet having a honeycomb structure or a plurality of bubbles scattered therein.

The present invention will be described in detail below based on the accompanying drawings.

FIG. 1 shows an example in which a honeycomb or foamed ceramic sheet 3 is integrally wound around the outer peripheral surface of a ceramic crawler core 1 on which a heating conductor 2 is formed, and an offset prevention layer 4 is further coated on the surface. The detailed structure of the heating fixing roller A according to the embodiment of the second invention will be explained according to the following manufacturing procedure.

First, the roller core 1 is formed by extrusion molding a ceramic material with excellent heat resistance, thermal conductivity, and electrical insulation properties, such as a raw ceramic material containing alumina as a main component. Next, the heating conductor 2 is printed by screen printing or other thick film technique using a conductor paste such as tungsten or molybdenum.

Next, a raw ceramic sheet 3 formed in a honeycomb structure or a foamed shape with a plurality of air bubbles scattered is wound around the entire outer periphery of the roller core 1 on which the heating conductor 2 is printed, and then The roller core 1 and the raw ceramic sheet 3 are sintered and integrated by firing in a reducing atmosphere.

It is preferable that the ceramic sheet 3 is made of the same material as the roller core 1, and its thickness is set to a size that allows it to exhibit a good heat storage effect. Specifically, it is not constant because it changes depending on the diameter, rotation speed, and circumferential speed of the roller core 1.

Then, the outer peripheral surface of the sintered and integrated ceramic sheet 3 is coated with a dense anti-offset layer 4 made of silicone rubber or fluororesin having excellent releasability and heat resistance.

According to this embodiment, since the ceramic sheet 3 having a heat storage effect is interposed between the offset prevention layer 4 and the heat generating conductor 2 which are in contact with the toner image, the heat generated from the heat generating conductor 2 is directly prevented from offset. The heat is temporarily stored in the ceramic sheet 3 without being transmitted to the layer 4, and after homogenizing the temperature distribution on the surface of the sheet 3, the heating fixing roller A is used to conduct heat to the offset prevention layer 4. The temperature distribution on the outer peripheral surface becomes uniform, and the toner image on the recording paper passing through the heat fixing roller A is well fixed.

Furthermore, since the ceramic sheet 3 also has a heat-insulating effect, it can prevent heat loss from the outer peripheral surface of the heat-fixing roller A, and reduce the heat generation capacity of the heat-generating conductor 2 to reduce power consumption. things become possible.

Incidentally, in this embodiment, the roller core body 1 can also be formed to have a honeycomb structure, and in this case, the weight of the heat fixing roller A can be reduced.

Fig. 2 shows a heating fixing roller B according to an embodiment of the first invention, in which the roller core itself is formed of a ceramic body having a heat storage effect. A roller core body made of a ceramic resistor such as PTC having temperature characteristics.The core body 11 is formed of a hollow cylindrical body having a honeycomb structure, and the outer peripheral surface thereof is coated with the aforementioned offset prevention layer 12. .

Such heating fixing roller B is
As described in detail in No. 73772, a rotating shaft 13 is inserted and fixed in the hollow space of the roller core 11, and the roller core 11 is inserted on both sides of the rotating shaft 13.
A power supply means 14 is fixedly provided in contact with both ends, and the roller core 1 is supplied from an external power source via the power supply means 14.
By supplying power to the roller core 11, the roller core 11 itself can generate heat.

According to this embodiment, since the roller core 11 itself, which has a heat generating effect, has a heat storage effect, the same effect as in the above embodiment can be obtained, and the roller core 11 itself is formed in a honeycomb structure. Therefore, it is possible to achieve weight reduction, and it is also possible to reduce costs by saving PTC ceramic material.

Furthermore, according to this embodiment, since the roller core 11 has a honeycomb structure, that is, it is not a dense structure but has an air layer, the heat generation capacity per unit volume can be small, and the roller core 11 can be used to form a toner image. Preheating time required to generate heat to the temperature required for fixing is shortened.

As is clear from the description of the above embodiments, all of the present inventions are made of ceramic rollers that have a heat storage layer formed at least on the outer layer side, which has a heat storage effect by having a honeycomb structure or a plurality of air bubbles scattered therein, and are densely packed on the surface. Since the offset prevention layer is formed, it is possible to achieve uniform temperature distribution on the outer peripheral surface of the roller, prevent heat loss from the outer peripheral surface, and reduce power consumption.

The roller is hard because it is a ceramic roller rather than a foamed resin roller as disclosed in JP-A-49-81041, for example.
Therefore, stable fixing efficiency can be maintained over a long period of time without causing deterioration over time such as permanent distortion.

The hardness of the ceramic roller reduces the nip width between it and the pressure roller, preventing paper wrinkles and skew.

On the other hand, if the nip width becomes smaller, there is a risk that fixing failure will occur due to a drop in temperature of the roller immediately after contact with transfer paper or unfixed toner. , the temperature drop of the roller immediately after contact is reduced.

Furthermore, in the first invention, since the ceramic roller itself is configured to generate heat, in other words, energy is always supplied near the contact surface, so there is no risk of the temperature of the roller decreasing immediately after contact. Defects are completely prevented.

Furthermore, the first aspect of the present invention has the effect of reducing the weight of the heat fixing roller itself, reducing the heat generating capacity per unit volume, and shortening the preheating time.

On the other hand, in the second invention, unlike the first invention, the ceramic crawler itself is not formed of a heating element, but instead of having a heater tube on the center side of the roller like a conventional heat fixing roller, the ceramic crawler Since the heating conductor is located in direct contact with the outer peripheral surface of the core, in other words, the inner peripheral side of the ceramic sheet that functions as a heat storage layer directly under the offset prevention layer, it is substantially the same as when the heat storage layer generates heat. It is possible to provide the same function and achieve the same effects as the first invention.

Therefore, all of the above-mentioned inventions can smoothly achieve the object of the present invention, and have extremely great practical value.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view showing a heat fixing roller according to an embodiment of the second invention, FIGS. 2A and 2B show a heat fixing roller according to an embodiment of the first invention, and FIG. 2A is a The vertical cross-sectional view, FIG. 2B, is a cross-sectional view taken along the line Y-Y' in FIG. 2A.

Claims (1)

[Scope of Claims] 1. In a heating fixing roller that is equipped with a heating element inside and performs heat fixing while bringing an unfixed toner image into contact with its outer peripheral surface, a ceramic resistor having a honeycomb structure and positive temperature characteristics is used. A heat fixing roller characterized in that an offset prevention layer is coated on the outer peripheral surface of the roller. 2. In a heating fixing roller that is equipped with a heating element inside and performs heat fixing while bringing an unfixed toner image into contact with its outer peripheral surface, a honeycomb structure or a plurality of bubbles are formed on the outer peripheral surface of a ceramic crawler core that has a heat generating conductor formed on its outer peripheral surface. 1. A heat fixing roller characterized in that an offset prevention layer is coated on the outer circumferential surface of a ceramic roller having a two-layer structure formed by integrally wrapping ceramic sheets in which ceramic sheets are scattered.