JPS59155872A - Heat fixing device - Google Patents

Abstract

PURPOSE:To shorten a preheating time and to prevent the generation of an electric conduction fault from an electrode by providing the electrode on both end parts of a heating roll, and constituting it so as to contact with a pressure roll between these electrodes. CONSTITUTION:A heating roll 1 and a pressure roll 2 which are press contacted to each other are rotated by a driving mechanism, and when a voltage is impressed to a feed brush from a commercial AC power source, a current flows to a resistance heating element layer 8 through annular electrodes 9, 9a, to heat the heating roll 1. By heating directly the heating roll 1 in this way, power consumption is reduced, and also the preheating time is shortened. Also, the annular electrodes 9, 9a are provided on both end parts of the heating roll 1, and the pressure roll 2 is made contacted by pressing and welded to the heating roll 1 between these electrodes, therefore, a toner scarcely sticks to the annular electrodes 9, 9a. In this way, the preheating time is shortened, and generation of conduction fault is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat fixing device, and in particular, to an image forming apparatus such as an electronic photocopier, a facsimile A5, and a printer, which is used to fix images on a support such as paper. The present invention relates to a heat fixing device for fixing a toner image using a heating roll and a pressure roll.

A3 in the image forming device (as one of the 11 device rows, there is an infrared lamp, a halogen lamp and a body 1 inside)
Is there a heat source such as a beam? The so-called heat roller is equipped with a heating roll and a pressure roll in which the surface of a metal core with good thermal conductivity is coated with a layer of heat-resistant elastic material such as silicone rubber or a layer of Teflon (trade name). Roll-type heat fixing devices are known.

In this type of heat fixing device, the heat roller body is indirectly heated by the radiant heat from the heat source inside the heating roll through the air, resulting in poor thermal efficiency, and the surface of the heating roll reaches a predetermined fixing temperature ( Tsutomi had the disadvantage of a long preheating time (approximately 3 to 5 minutes) to reach a temperature of about 150 to 180°C.In order to shorten this preheating +1;'l IiS], for example, It has been proposed to directly heat the roll body with a resistance heating element such as a ceramic heater as described in Japanese Patent Application Laid-open No. 56-123581 and Japanese Patent Application Laid-Open No. 56-138766.

Although this direct heating type fixing device can shorten the preheating time compared to the conventional radiation heating type, it still
2 minutes &! Maro needed time to warm up.

Furthermore, as resistance heating elements, ceramic heating elements having a positive temperature coefficient of resistance, so-called TC characteristics, are well known. This laminate heating element with PTC characteristics has the following features: a predetermined heat generation temperature can be obtained by selecting the Curie temperature, a rapid temperature rise time, and a rapid increase in resistance at a constant temperature, so that the self-temperature It has advantages such as having a control function.

However, the generally known Ba Ti 03-based ceramic heating element is difficult to manufacture, and it has not been put into practical use due to the fact that it requires a lot of rotation to obtain one with high dimensional accuracy. Not done.

Improvements to this type of ceramic heating element have also been made, for example, in JP-A-55-164.859 and JP-A-56-138766.
However, these proposals are not sufficient.

The present invention solves the problems of the prior art as described above, significantly shortens the preheating time, and prevents normal energization from being impossible due to toner adhering to the power supply electrode to the heating roll. Its purpose is to provide a heating chamber @ device that prevents heating.

The features of the present invention include a heating roll having a resistance heating layer;
In a fixing device configured such that a support holding a 1-toner image is passed between a pressure roll that is in pressure contact with the heating roll, electrodes are provided at both ends of the heating roll, and an electrode is provided between the electrodes. The heating fixing device is configured to be in contact with the pressure 1]-ru.

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

Here, FIG. 1 shows a heating chamber @ device according to an example.
11 is a longitudinal sectional front view, and FIG. 2 is a sectional view taken along the line A-A in FIG. 1.

On the same side - C11 is a heating roll, 2 (a pressure roll,
3.3aJ3 and 3b, 3c1. t, each bearing, 4
．． Reference numeral 4a denotes side plates; the heating roll 1 is rotatably supported by the side plates 4, 4a via bearings 3.degree. 3a, and the pressure roll 2 is rotatably supported by the side plates 4, 4a via bearings 3b, 3c.

5. Heat! Metallic hollow core constituting call 1, 6
is a bonding layer, 7 is an insulating layer, 8 is a resistance heating layer, and is hollow)
15 with a bonding layer 6 and an insulating layer 7 interposed therebetween. Reference numerals 9 and 9a denote ring-shaped electrodes made of a conductive material such as C1 alloy, which are mounted near both ends of the outer peripheral surface of the resistance heating layer 8 with a gap slightly larger than a predetermined fixing width. The ring-shaped electrodes 9, 9a are in contact with a power supply brush (not shown) such as a ferrule, which is connected to a power source through a wire connection. Reference numeral 10 denotes an M-type layer formed on the outer peripheral surface of the resistance heating layer 8 to a length corresponding to the fixing width.

11 is a metallic hollow core constituting pressurization [1-ru 2;
Reference numeral 12 denotes a heat-resistant elastic layer formed by covering the outer peripheral surface of the hollow core 11, each having a gap of a predetermined fixing width, and heated between the ring-shaped electrodes 9.9a of the heating roll 1. Roll 1 makes contact.

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

The resistance heating element layer 8 can be put to practical use by forming it from R;02 ceramic. The 7i02 series ceramic is represented by the chemical formula T102-X (0≦X<1), and as x becomes larger, the specific resistance becomes smaller.

In this case, by controlling the production atmosphere, TtO
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 TlO2-based ceramic are that it has excellent corrosion resistance, low power consumption (about 40V In addition to the advantages, it is also possible to easily form a resistive film by plasma spraying using raw material powder. In other words, with the 7i02-based ceramic, plasma spraying can be applied as a means of forming a resistive film, so the manufacturing cost is significantly lower than that of the BaTiO3-based ceramic, and the cost is equivalent to or equivalent to that using a conventional radiant heat source. It is now possible to manufacture a heating roll in step 1 below. However, TlO2-based ceramics have a negative temperature coefficient of resistance, meaning that the resistance decreases as the temperature increases, so when a certain humidity is reached between the resistance heating element layer and the input power source, It is necessary to incorporate a control circuit that stops energization.

The insulation m7 is for electrically insulating the resistance heating element layer 8 and the hollow core 5 by 1q, and various materials can be used, but when the resistance heating element layer 8 is made of TiO2 ceramic, AJI! 203.MqO is suitable.

The bonding layer 6 serves to securely fix 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 above-mentioned resistance heating layer, insulating layer, and bonding layer may be set as appropriate depending on the fixing temperature, the 4-layer composition, the mowing of the hollow core (length, outer diameter, inner diameter), etc. . For example, the hollow core is 270mm (length) x 34.5mmφ (outer diameter) 3
When the fixing temperature is 190 to 210°C with a diameter of 2nl (inner diameter), the resistance heating layer (Ti 02 ) is 50 to 70μ.
m, the insulation layer (△1203・M(10) is 150~
200 um Vl ra, and a bonding layer (Ni-A
ρ-Mo) is suitably about 50 μm.

Next, the fixing operation of the heating chamber@device having the above configuration will be explained.

First, when the heating roll 1 and the pressure roll 2 that are in pressure contact with each other are rotated by a drive mechanism (not shown), and voltage is applied to the power supply brush from a commercial AC power supply, the resistance is passed through the ring-shaped electrodes 9 and 9a. A current flows through the heating element layer 8 and the heating roll 1 is heated. Here, when a support holding toner is passed between the heating roll 1 and the pressure roll 2, images 1 to C are fused onto the support to form a fixed image 151.

The 1-boo image is fused onto the support by providing ring-shaped electrodes 4fi9 and 9a at both ends of the heating roll 1, and pressing the pressure roll 2 onto the heating roll 1 between these electrodes. Therefore, toner is less likely to adhere to the ring-shaped electrodes 9, 9a, and there is no problem in current flow.

In addition, in the heating tool 1, a heat-resistant elastic layer such as silicone rubber may be formed on the resistance heating layer 8, and a release layer such as Teflon may be formed therebetween.

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.

The above-described J: uni, heat fixing device e according to the present embodiment
+ forms a resistance heating element layer 8 on the outer periphery of a metal hollow core 5 via a bonding layer 6 and an insulating layer 7;
The pressure roll 2 is pressed between the electrodes 9°98 to the heating roll 1, which has ring-shaped electrodes 9, 9a attached near both ends of the outer circumferential surface of the heating roll 1. When fixing, the toner forms a ring '21151! ff19
．． 9a is rarely served, so there is no problem with the electricity flowing from the electrodes.

As described above, the present invention can be expected to provide a heat fixing device that can significantly shorten the preheating time by 9a and that does not cause any trouble in supplying electricity to the heating roll. It can be said that this invention is highly effective.

[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 A-Δ in FIG. 1... Heating roll, 2... Pressure roll, 9.9a.
...Ring-shaped electrode.

Claims (1)

[Claims] The resistance heating element layer is heated by passing through a support 1.5 with a holding hole of 1 to 4 Kr between the heating roll and the pressure roll that presses against the heating roll. The heating roll is characterized in that the heating roller is provided with 8 electrodes at both ends of the heating roll, and the electrodes are in contact with the pressure roll between the electrodes. Room @ equipment.