JPS59155874A - Heat fixing device - Google Patents

Abstract

PURPOSE:To shorten a preheating time and also to prevent the generation of an electric conduction fault by forming a stepped part on the end face of a hollow core to constitute so that a pressure roll is press-contacted to a heating roll providing an annular electrode press-contacting to a resistance heating element layer on its stepped part. CONSTITUTION:The heating roll 1 and the pressure roll 2 which are press-contacted to each other are actuated and when a voltage is impressed from an AC power source, a current flows to a resistance heating element layer 10 through the annular electrodes 11, 11a, and the heating roll is heated directly to reduce, the preheating time. Also, the annular electrodes 11, 11a are mounted on the stepped parts 7, 7a provided on the end face of the heating roll 1, and between these electrodes, the pressure roll 2 is made contacted by pressing to the heating roll 1 to weld a developed picture, therefore, a toner scarcely sticks to the annular electrodes 11, 11a, and no fault is generated in the electric conduction. In this way, the preheating time is shortened, and also the generation of an electric conduction fault is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat fixing device, and particularly to a heat fixing device for heating a toner image formed on a support such as paper in an image forming device such as an electronic copying machine, a facsimile machine, and a printer. The present invention relates to a heat fixing device defined by one call and a pressure roll.

As one of the fixing devices in image forming apparatuses, a heat-resistant elastic material layer such as silicone rubber or a heat-resistant elastic material layer such as DEFRON (product name ) etc.
A so-called heat roll type heat fixing device 71 is known, which includes a heat roll coated with an L-type layer and a pressure roll.

In this type of heat fixing device, the roll body is indirectly heated through the air by the radiant heat from the heat source inside the heating roll, so thermal efficiency is poor, and the surface of the heating roll reaches a predetermined fixing temperature (usually 150 to 180 There was a drawback that the preheating time required to reach the "C position" was long (3 to 5 minutes culm strength).In order to shorten this preheating time, for example, Japanese Patent Laid-Open No. 56-123581 and Kaisho 56-1387
It has been proposed to directly heat the roll body using a resistance heating element such as a Reramic heater as described in Japanese Patent No. 66 and the like.

According to this direct heating type fixing device, the preheating time can be shortened compared to the conventional one-wheel heating type, but a preheating time of 1 to 2 minutes is still required.

Furthermore, as a resistance heating element, a ceramic heating element having a positive temperature coefficient of resistance, a so-called PTC characteristic, is known. This ceramic heating element with PTC characteristics has a self-temperature control function because the predetermined heat generation temperature can be adjusted by 1q by selecting the Gully humidity, the temperature rise time is fast, and the resistance increases rapidly at a constant temperature. It has advantages such as:

However, the commonly known 13aT! Oa-based ceramic heating elements have not been put into practical use because they require time and effort to manufacture, and it is extremely difficult to produce one with high dimensional accuracy in a weight of 1 g.

In addition, improvements to this type of ceramic heating element have been proposed, for example, in Japanese Patent Application Laid-open Nos. 164859-1985, 138766-1980, and 123581-1981, but these are not enough. It is impossible.

The present invention solves the problems of the prior art described above, can significantly shorten the preheating time, and also makes it possible to significantly shorten the preheating time.
It is an object of the present invention to provide a 1"1 heat fixing device which prevents normal energization from being impossible due to 1 to ner (=J=i8'!) being applied to the power supply electrodes.

A feature of the present invention is that a support holding a toner image is passed between a heating roll having a resistance heating layer and a pressure roll that presses against the heating roll. In the fixing device, a stepped portion is formed on an end surface of the heating roll,
An electrode is provided on the stepped portion in the heat fixing device.

Examples of the present invention will be described below with reference to the drawings. I will clarify.

Here, FIG. 1 shows +Jrl heat constant W R according to one embodiment.
:? '4 partially longitudinal front view, Figure 2 is taken along A-A in Figure 1.
It is an arrow sectional view.

In the figure, 1 is a heating roll, 2 is a pressure roll, 3,
3aJ5, 3b, and 3c are pile bearings, 14at,
On one side plate, the heating roll 1 is rotatably supported by the side plates 1 and 4a via bearings 3.degree. 3a, and the pressure roll 2 is rotatably supported by the side plates 4 and 4a via bearings 3b and 3c.

5 is a metal hollow core that constitutes the heating roll 1; 6.
Reference numeral 6a denotes stepped portions formed at both ends of the hollow core 5, and constitutes stepped portions 7, 7a on the end surface of the heating roll '1. 8 is a bonding layer, 9 is an insulating layer, and 1o is a resistance heating layer (e). 11.
Reference numeral 11a denotes a ring-shaped electrode made of a conductor h+t made of a Cu alloy or the like, and is attached to the stepped portion 7.7a of the heating roll 1. The ring-shaped electrodes 11.11a are each connected to a power supply brush (not shown) made of carbon or the like connected to a power supply via a wire connection.
is in contact with. Reference numeral 12 denotes a releasable layer having a Ct shadow formed on the outer periphery of the resistance heating layer 10 with a length corresponding to the fixing width.

13 is a metallic hollow core that constitutes the pressure roll 2;
Reference numeral 14 denotes a heat-resistant elastic layer formed to cover the outer periphery of the hollow core 13, each having a gap of a predetermined fixing width and in contact with the heating roll 1.

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

The resistance heating element layer 10 can be put to practical use by forming it with a TiO2 ceramic heating element.

TiO2-based ceramics are represented by the chemical formula Wang IC)2-x (0≦X·g1), and as X becomes larger, the specific resistance becomes smaller. In this case, control the production atmosphere uIr ;r
By doing so, it is possible to adjust × of T102-x,
For example, the stronger the reducing nature of the atmosphere, the larger x becomes. The characteristics of this IO2 series ceramic are that it has excellent corrosion resistance and low power consumption (71.0 V x 5 A or 5
0V In addition to obtaining a 4-degree surface of the melon, in particular, J:
One reason for this is that it is not easy to form a resistive film. According to Zunawara's TiO2-based ceramic, plasma spraying can be applied as a means of forming a resistive film, so Ba1-i
o The production cost is significantly reduced compared to 3 series ceramics, and it is possible to produce heating rolls at the same or lower cost than when using conventional heat sources. has a negative resistance wetting coefficient in which the resistance decreases as the temperature increases, so when a predetermined temperature is reached between the resistive heating element layer and the input power source, the heating element layer It is necessary to incorporate a control circuit that stops energization of l\.

The insulating layer 9 is for obtaining electrical insulation between the resistive heating element layer 10 and the hollow core 5, and can be made of various materials, but when the resistive heating element layer 10 is made of TiO2 ceramic, Δ1203・MqO/)<Appropriate.

The bonding layer 8 is for securely fixing the insulating layer 9 to the hollow core 5, and may be omitted depending on the materials of the hollow core 5 and the insulating layer 9.

The thicknesses of the resistive heating element layer, insulating layer, and bonding layer can be appropriately set according to the fixing temperature, material (composition), χ1 method (length, outer diameter, inner diameter) of the hollow core, etc. For example, the hollow core is 270mm (length) x 34.5mmφ (outer diameter)
When the diameter is 32 mmφ (inner diameter) and the fixing temperature is 190 to 210°C, the resistance heating layer (Ti 02 ) is 50 to 70 μm.
IIIPi! The insulation layer (Ai20a/MQo) is
about 150 to 200 ttrn, and a bonding layer (Ni −
Ai-MO) is suitably about 5 Q μm.

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

First, the heating roll 1 and the pressure roll 2 are rotated by a drive mechanism (not shown), and a commercial AC voltage is applied to the power supply brush from a commercial source. A current flows through the resistive heating element layer 10 through the shaped electrodes 11 and 118, heating the heating roll 1.

Here, 1 is placed between C1 heating roll 1 and pressure roll 2.
- When passing through the support carrying the toner image, the Lee image is fused onto the support to form a fixed image.

The heating roll 1
A ring-shaped electrode 11.118 is installed on the stepped portions 7, 7a of
Since the pressure roll 2 is brought into pressure contact with the heating roll 1 between the electrodes and fused, it is less likely that 1 to 1-ner will adhere to the ring-shaped electrode 11, 11a, and there will be no problem with current conduction.

J3, the heating roll 1 may be formed by forming a heat-resistant elastic layer such as silicone rubber on the resistance heating layer 10, and forming an Ill-type layer such as Teflon on top of the heat-resistant elastic layer.

On the other hand, the hardened silicon roll 2 may also be one in which a heat-resistant elastic layer is formed on a solid metal core.

As explained above, the heat fixing device according to this embodiment is
A resistance heating layer 10 is provided on the stepped portions 6, 6a of the metal hollow core 5.
Since the pressure roll 2 is pressed into contact with the heating roll 1 equipped with a ring-shaped electrode 11.118 in contact with the J: sea urchin,
Since the fixing of the toner image on the support is less likely to cause the toner to adhere to the ring-shaped electrodes 11, 11, a, there is no problem in the conduction of electricity from the electrodes.

As described above, the present invention provides a heat fixing device that can significantly shorten the preheating time and that does not cause any trouble in supplying electricity to the +II heat roll. This invention can be said to have excellent practical effects.

[Brief explanation of the drawing]

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 A--Δ in FIG. 1... Heating [1-roll, 2... Pressure roll, 7.7a
...Stepped portion, 11.11a...Ring-shaped electrode. Patent applicant [l Ritsu Kinzoku Co., Ltd. Agent]

Claims (1)

[Claims] Heating with a resistance heating element layer [1-ru and the heating 1]-
In a constant @ device configured to pass a support holding a color image between a pressure roll and a pressure roll,
A heat fixing device characterized in that a stepped portion is formed on an end surface of the heating roll, and a voltage is provided on the stepped portion.