JPS59149384A - Heat fixing device - Google Patents

Abstract

PURPOSE:To shorten considerably a preheating time and attain a uniform heating temperature throughout the overall length of a heat roll by providing a resistance heating body layer up to the shaft part of the heat roll and providing an electrode in the shaft part. CONSTITUTION:Annular electrodes 9 and 9a brought into contact with resistance heating body layer 8 are provided in the shaft part of a heat roll 1 where the resistance heating body layer 8 is formed on the outside circumference, in both side face parts, and in the shaft part of a metallic hollow core 5 through a coupling layer 6 and an insulating layer 7. If the resistance heating body layer 8 is formed with a TiO2 ceramic, a surface temperature of about 200 deg.C is attained in a short time with low power consumption. When the roll 1 and a pressure roll 2 are rotated and a voltage is impressed to a feeding brush, a current is flowed to the layer 8 through the electrodes 9 and 9a to heat the roll 1. Since the layer 8 is formed on the outside circumference from both side face parts to the shaft part of the roll 1, the temperature distribution on the surface of the roll 1 is kept uniform practically.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat fixing device, and in particular, in an image forming apparatus such as an electrophotographic copying machine, a facsimile machine, and a printer, a dove image formed on a support such as paper is transferred to a heating roll. The present invention relates to a heat fixing device that performs fixing using a pressure roll and a pressure roll.

As one of the fixed @ devices in an image forming apparatus, a heat-resistant elastic layer such as silicone rubber or Teflon (commercial product A so-called thermal fixing device is known, which is equipped with a heating roll and a pressure roll coated with a releasable layer such as the following.

In this type of heat fixing device, the inside of the heating roll is
Since the roll body is heated indirectly through the air by the radiant heat of the heat source, thermal efficiency is poor, and it takes a long time to preheat the heated roll surface until it reaches the specified fixing temperature (usually around 1550 to 180°C). (about 3 to 5 minutes). In order to shorten this preheating time, for example (J
, JP-A-56-123581 and JP-A-56-13
It has been proposed to directly heat the roll body using a resistance heating element such as a ceramic heater as described in Japanese Patent No. 8766.

Although this direct heating type constant @ device can shorten the preheating time compared to the conventional radiation heating type, it still
A preheating time of 2 minutes is required, and it is less than 1 degree. Furthermore, as a resistance heating element, a ceramic heating element is known which has a positive temperature coefficient of resistance, or a so-called PTC characteristic. This PTC
The Leramitsu heating element has the following characteristics: a predetermined heat generation temperature can be obtained by selecting one temperature, a fast temperature rise time, and a self-temperature control function because the resistance increases rapidly at a constant temperature. There are advantages such as:

However, the generally known 3a Ti 03 series ceramic heating element is time-consuming to manufacture, and also has a limited usage method.
It has not been put to practical use because it is extremely difficult to obtain a truly expensive product.

In addition, improvements to this inserted ceramic heating element have been proposed, for example, in various publications such as JP-A-55-164859, JP-A-56-1387G6, and JP-A-56-123581. It is something that cannot be separated.

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat fixing device that can eliminate the problems of the prior art as described above, significantly shorten preheating time, and obtain a uniform heating temperature over the entire length of a heating roll. That is.

The characteristics of the present invention include a heating roll having a resistance heating layer,
The toner (
In the fixing device configured as above, the resistive heating layer is provided up to the shaft of the heating element, and an electric current (1) is provided on the shaft. It's in the fixing device.

Embodiments of the present invention will be described below based on the drawings.

Here, FIG. 1 is a partially vertical front view of a heat fixing device according to an embodiment, and FIG. 2 is a sectional view taken along the line A--Δ in FIG.

In the figure, 1 is a heating roll, 2 is a pressure roll, 3,
3a, 3b, 3c are the respective bearings, 4.4a is the side plate, the heating roller 1 is connected to the side plates 4, 4a via the bearing 3.3a, and the pressure roll 2 is connected to the bearings 3b, 3c. Each is rotatably supported by the side plate 4.4a via the side plate 4.4a.

5 is a metal hollow core that constitutes the heating roll 1; 6 is a bonding layer; 7 is an insulating layer; 8 is a resistance heating layer;
A bonding layer 6 and an insulating layer 7 are provided on the outer periphery, the side surface J3 and the shaft.
A resistive heating element layer 8 is formed through -C. 9.98
is a ring-shaped electrode made of a CU gold alloy conductor, and is attached in contact with the resistance heating layer 8 of the shaft part of the heating [1-1]. These ring-shaped electrodes 9 and 9a each have a connection tfA10
7 connected to the power supply (tq −++” shown) through
It is in contact with a power supply brush such as a J-bon. Reference numeral 12 denotes a releasable layer formed on the outer peripheral surface of the resistance heating layer 8.

13 is a metal hollow core constituting the pressure roll 2;
Reference numeral 71 denotes a heat-resistant elastic layer formed to cover the outer peripheral surface of the hollow core 13.

Next, details of each component of the heating roll 1 described above are as follows.

The resistance heating layer 8 can be put to practical use by forming it from TiO2 ceramic. The 1-102 series ceramic is represented by the chemical formula TiO2-x (0≦x<1), and as X becomes larger, the specific resistance becomes smaller. In this case, I decided to control the production atmosphere, T! 0
It is possible to adjust X in 2-x, and for example, the culm X becomes larger when the reducing nature of the atmosphere becomes stronger. The characteristics of this Fiz2 ceramic are that it has high corrosion resistance, low power consumption (about 40VX5Δ or 50VX6Δ), C1, and can achieve a surface temperature of about 200℃ in a short time (several seconds to tens of seconds). Another advantage is that a resistive film can be easily formed by plasma spraying using raw material powder. In other words, with TiO2-based ceramics, plasma spraying can be applied as a means of forming a resistive film, so the manufacturing cost is significantly reduced compared to B a T and i03-based ceramics, and when conventional radiant heat sources are used. It is possible to manufacture heating rolls at a cost equal to or lower than that of . However, TiO2-based ceramics have a negative temperature coefficient of resistance, meaning that the resistance decreases as the temperature increases, so when a predetermined temperature is reached between the resistance heating layer and the input power source, heat is generated. It is necessary to incorporate a control circuit that de-energizes the body layers.

The insulating layer 7 is for electrically insulating the resistive heating element layer E3 and the hollow core 5, and can be made of various materials, but when the resistive heating element layer 8 is made of TiO2 ceramic, AJ1203. MIJO is suitable.

The bonding layer 6 is for securely fixing the insulating layer 7 to the hollow core 5, and may be omitted depending on the materials of the hollow core 5 and the insulating layer 7.

The thicknesses of the resistance heating layer, insulating layer, and bonding layer may be appropriately set depending on the fixing temperature, the material (11-layer), the dimensions (length, outer diameter, inner diameter) of the hollow core, and the like. For example, the hollow core is 270111n+ (length) x 34.5+nmφ
(outer diameter) 32 nunφ (inner diameter), fixing temperature 19
In the case of 0 to 210'C, resistive heating element layer (Ti 02
) is about 50 to 7 Otim, 1lli<A, σ203・
Appropriately, the thickness of Mgb) is about 150 to 200 l1m, and the bonding layer (Ni-Δρ-Mo)t is about 150μ. .

Next, the fixing operation of the heat fixing device configured as described above will be explained.

First, when the heating 1-ru 1 and the pressurizing 1-ru 2 are rotated by a drive mechanism (not shown), and a voltage is applied to the power supply brush from a commercial AC power source, the ring-shaped electrode 9, A current flows through the resistance heating element layer 8 through the heating element layer 9a, and the heating element 1 is heated.

For this heating Gj, the resistance heating layer 8 is formed on the outer periphery of the heating roll 1 from both side surfaces to the shaft, so that the temperature distribution on the surface of the heating roll 1 is kept substantially uniform. The temperature drop at both ends is compensated for.

Therefore, when the support holding the toner is passed between the heating roll 1 and the pressure roll 2, a high-quality fixed image 1q without defective fixing at both ends is obtained.

In the heating roll 1, a heat-resistant elastic layer such as silicone rubber may be formed on the resistance heating layer 8, and a releasable layer such as Teflon may be formed thereon.

On the other hand, the pressure roll 2 may be one in which a heat-resistant elastic layer is formed on a solid metal core, in addition to the above.

As explained above, the heat fixing device according to this embodiment is
A heating roll 1 has a resistance heating layer 8 formed thereon through a bonding layer 6 J3 and an insulating layer 7 on both side surfaces a3 of the outer periphery 1 of a metal hollow core 5 and on the shaft. There is also one equipped with a ring-shaped electrode 9.98.

Therefore, if power is supplied from the power source to the ring-shaped electrodes 9, 9a via the power supply brush 11, the temperature distribution on the surface of the heating roll 1 will not decrease at both ends, and will be kept uniform. A high-quality fixed image with no fixation defects can be obtained.

As described above, the present invention can significantly shorten the preheating time and provide a heat fixing device that can provide a uniform heating temperature over the entire length of the heating system. Therefore, it can be said that the invention has excellent practical effects.

[Brief explanation of drawings]

FIG. 1 is a partially longitudinal sectional front view of a heat fixing device according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along the line AA in FIG. 1. 1... Heating roll, 2... Pressure [l-ru, 8...
Resistance heating element layer, 9, 9a... ring-shaped electrode.

Claims (1)

[Claims] In a fixed @ apparatus configured to pass a support holding a toner image between a heating roll having a resistive heating element layer and a pressure roll that is in pressure contact with the heating roll, the resistive heating element layer A heating constant @ device, characterized in that the heating roller is installed up to the shaft portion of the heating roll, and an electrode is provided on the shaft portion.