JPS59155875A - Fixing device - Google Patents

Abstract

PURPOSE:To reduce the ununiformity of a temperature distribution in the axial direction and the deformation due to the press-contact of a press-contacting roller by forming plural projecting parts projected to the inside on the inside surface of a heating roller to extend in a roller axial direction. CONSTITUTION:A long-sized heater 2 is installed in a heating roller 10, and the roller 10 is heated by said heater, but on its inside surface, plural projecting parts 10a projected to the inside are extended in the longitudinal direction of the roller to form. According to this constitution, heat accumulated in a range X in which a transfer material does not pass through can reduce the temperature difference to the part of a width B5 to a degree (b) which is allowed for a practical use by a large thermal conductivity in a thick part having the projecting part 10a. On the other hand, the deformation based on a press-contact operation by a press-contacting roller 3 can also be reduced. In this way, the ununiformity of the temperature distribution in the axial direction becomes small, and the deformation by the press-contacting oeration is also reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat fixing device used in image forming apparatuses such as electrostatic copying machines and printers.

A fixing means that electrostatically forms an image on the surface of a transfer material using powdered or liquid developer (hereinafter referred to as toner) and fixes this toner image to the transfer material by thermofusion, for example, A method in which a transfer material is passed between a pair of rollers as shown in Figure 1 has been widely used in the past. As shown in the figure, this type of fixing means includes a hollow cylindrical heating roller 1 having a tubular heater 2 inside, and a pressure roller 3 whose outer surface is covered with a relatively flexible material 4 such as rubber. Then, the two are pressed against each other to form a nip 6 at the abutting portion of the two, and the transfer material P carrying the toner is run in the direction of the arrow claw in the figure to pass through the nip 6, and the heater 2 The toner is fused and fixed to the transfer material by the suppressing action between the roller 1 and the pressure roller 2, which are maintained at a predetermined temperature in advance. In this case, the surface of the heating roller 1 may be completely coated with a Teflon (trade name) layer to prevent offset, or a silicone rubber layer with good thermal conductivity to provide sufficient heat to the toner. Are known. j
Usually, stainless steel or aluminum materials are used for roller j profiteering, but in any case,
During image forming work, in order to minimize the wait time from energizing the heater until the surface of the row 91 reaches a predetermined temperature, it is best to form the cylindrical base material as thin as possible. It's normal.

However, when performing image forming operations, fixing means having such a configuration is rarely used for fixing operations over the entire length of the pair of rollers extending perpendicular to the paper surface; In order to make it possible to use multiple types of transfer materials with different types of transfer materials, the fixing roller pair naturally has a length that allows the transfer of the maximum amount of transfer material. Transfer materials smaller in size are often used. FIG. 2A is a plan view illustrating this, and in the case shown, the roller 1 has a length capable of processing a transfer material having a width of A3, and in such a fixing means, for example, from this When a transfer material with a narrow width B5 is frequently used, the difference between the two is that the roller pair is simply heated at a location corresponding to The surface temperature tends to rise. The 'tZ2B diagram is a graph that summarizes this tendency, and although the desired fixing temperature is generally maintained in the width B5 range, the temperature in the range X is indicated by the symbol a in the diagram. Since the temperature rises significantly (sometimes exceeding 250°C), it may affect the Teflon layer and silicone rubber layer formed on the surface of the heating port, causing deterioration of their functions. In the case of a fixing means as shown in FIG. Therefore, heat resistance (250'C
Separation claws 5 made of resin (usually able to withstand a certain degree of deformation) are arranged, but the transfer material does not pass through the range X as described above.
Temperatures may exceed 250° C. at these points, which causes problems such as thermal deformation of the separating claws.

In order to eliminate such drawbacks, for example, the heating roller 1 may be made thicker to allow the transfer material to pass through it more easily.
135 area and area X, or the base material of the heating roller is configured to take advantage of the phase change between liquid and gas to transfer heat using latent heat. There have already been proposals that consist of pipes to maintain a uniform temperature distribution on the roller surface.
The former method naturally requires a long time (wait time) for the surface of the heating roller to reach a predetermined temperature, and the latter method is undesirable because it complicates the configuration and increases costs.

The present invention has been made in view of the current situation, and by forming a plurality of inwardly projecting protrusions on the inner surface of the heating roller 1, the axis of heat on the surface of the heating roller 1 can be adjusted. To provide a fixing mechanism which can eliminate as much as possible the above-mentioned non-uniformity in temperature distribution by promoting directional conduction, and can also reduce deformation due to the pressing action of a pressing roller 2. The purpose is to

FIG. 3 is a cross-sectional view of the fixing mechanism according to the present invention, showing the heating roller 1' (11), and FIG. 4 is a longitudinal cross-sectional view taken along the line IV--IV of FIG. 1. Like the one shown in Figure 1, the transfer material is in pressure contact with the pressure roller 3 shown by the chain line, and the transfer material passes through the two tabs 6 where both come into contact.
It is the same as that shown in figure A.

Heating Roller] A long heater 2 is installed inside the roller 10, which heats the roller 10, but in the roller 10 shown in FIGS. A plurality of protruding ridges (eight in the one shown)], O
A is formed to extend in the longitudinal direction of the roller. heating row 2
By configuring 10 in this way, the heat accumulated in the area It has become possible to reduce the size to an acceptable level.

According to the experimental results, the heating roller has a wall thickness of 2 tons.

If eight protrusions each having a radial length of 7 ms and a circumferential length of approximately 4 ms are formed on a diameter of 40φ, the temperature rise in range X can be suppressed to the extent of the curve shown in Figure 2B. Ta. Furthermore, in order to reach the same level of temperature rise in range X, the thickness of the heating roller needs to be 5 mm or more, and there is a significant difference in wait time.

In order to shorten the wait time, it is also good to make the inner surface of the heating port black to increase the heat absorption efficiency.

It is clear that the protrusion 10a formed inside the heating roller extends in the axial direction, so it has a reinforcing effect.
When a load of about 40 m is applied to a roller of 00 m,
In the case of known rollers of the same size, the amount of elastic deformation is up to 100
However, in the case of the uninvented roller, the moment of inertia of area is approximately 25 times, and the amount of elastic deformation is less than 50 microns. The negative effects on the transfer material can be reduced on the human body.

[Protrusions formed inside the heating roller], Oa is not limited to 8 parts as shown in Fig. 3, and the cross-sectional shape of each protrusion is only rectangular as shown in the figure. not(
Of course, it can be made into various shapes,
Further, the protruding portion 10a may be arranged in a spiral shape instead of simply extending in the axial direction on the inner surface of the roller.

Since the fixing mechanism according to the invention has the above-mentioned configuration, even if an image forming apparatus is used that particularly uses only a part of the longitudinal direction of the roller, the temperature distribution on the roller surface can be maintained as much as possible. Since it can be maintained uniformly, a good fixing action can be performed over a long period of time without the risk of damaging the Teflon layer on the roller surface. Since the amount of elastic deformation of the heating roller due to the pressure applied by the twisted pressure roller can also be reduced, it is possible to obtain the effect of preventing poor conveyance of the transfer material.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view showing the structure and operation of a known fixing mechanism, FIG. 2A is a plan view showing the relationship in the width direction of a pair of fixing rollers and different types of transfer material passing through them, and FIG. 2B is FIG. 3 is a side view showing an embodiment of the fixing mechanism of the present invention, particularly the heating roller. Figure 4 is clearly shown along line IV-IV in Figure 3 [1ill
It is a sectional view in the I-line direction. 1. Heat roller, 2. Heater, 3. Pressure roller,
5...Separation claw, 1 old heating roller, 10a...Protrusion. Patent applicant Canon Co., Ltd.

Claims (1)

[Claims] In a fixing device having at least a hollow cylindrical heating roller equipped with a heat source inside, and a pressure roller that presses against this roller, the heating roller has a plurality of inwardly projecting protrusions on the inner surface of the roller. A fixing device particularly characterized in that it extends in an axial direction.