JPS60128472A - Fixing device of heat roller - Google Patents

Abstract

PURPOSE:To prevent recording paper from the generation of wrinkles by crossing the axis of a fixing roller incorporating a heater and having the outer diameter of a center part smaller than that of both the end parts with the shaft of a press-contacting roller having a uniform outer diameter and holding the recording paper coated with a toner under pressure applied by the rollers to feed the paper. CONSTITUTION:The fixing roller 1 has the halogen pipe heater or a resistor heating body in its inside and the outer diameter of the center part is slightly smaller than that of both the end parts. For instance, the difference in diameter is properly 0.05-0.15mm. against 330mm. shaft length. The shaft of the press-contacting roller 2 is crossed with that of the fixing roller 1 within an angle alpha (alpha=0.3 deg.-1.5 deg.). In the shaft crossing, any one of the fixing roller 1 and press- contacting roller 2 may be set up rectangularly to the carrying direction of the recording paper or both the rollers may be inclined by alpha/2 each other. The diameter of the fixing roller 1 may be changed like a straight or curved line. Thus, the generation of wrinkles or waving phenomenon is reduced in the recording paper and a toner image is fixed easily and stably.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement of a heat roller fixing device used in a recording device such as an electrophotographic copying machine, and particularly to a heat roller fixing device that has a built-in heater and whose outer diameter is smaller than that of the central portion. This invention relates to an improvement in a device for fixing a toner image onto a recording paper by clamping and feeding a recording paper on which a toner image is attached by a fixing roller having larger ends and a pressure roller having a uniform outer diameter.

[Prior art]

The above-mentioned heat roller fixing device is known to improve the drawback of the heat roller fixing device, in which the outer diameter of the fixing roller is uniform, that wrinkles tend to occur on the recording paper. However, by making the outer diameter of the fixing roller larger at both ends than at the center, the recording paper warps, causing a large wave peg phenomenon, which causes further toner images to be recorded on the back side of the recording paper. Then, there is the problem of wrinkles appearing.

On the other hand, in a pressure roller fixing device that does not use a heater, a pair of clamping pressure rollers having a uniform outer diameter are mounted on bearings, as disclosed in JP-A-51-24236, JP-A-52-4845, and JP-A-54-139550. , Utsukai Sho 52-144744
It has been published in various publications. When this technology of bearings is applied to a heat roller fixing device in which the outer diameter of the fixing roller is also uniform, the pressure to clamp the recording paper increases the outer diameter of the fixing roller not only at the center but also at both ends. Contrary to the heat roller fixing device, large wrinkles and wrinkles are more likely to occur in the center than in both ends.

[Purpose of the invention]

The present invention was made in order to solve the above-mentioned problem in a heat roller fixing device in which the outer diameter of the fixing roller is made thicker at both ends than in the center, and is used in a pressure roller fixing device. This was done as a result of the discovery that when the cross-axis technology is applied to a hot roller fixing device in which the outer diameter of the fixing roller is larger at both ends than at the center, wrinkles and wave pegs are reduced.

[Structure of the invention]

That is, the present invention uses a fixing roller that has a built-in heater and whose outer diameter is larger at both ends than the center, and a pressure roller that has a uniform outer diameter to feed the recording paper with the toner image attached thereon while applying pressure to the fixing roller. In a device 6 for fixing images onto recording paper, there is a thermal roller fixing device "It" characterized in that the rollers are arranged so that their axes intersect with each other.

The fixing roller 1 in the heat roller fixing device of the present invention has a built-in heater such as a thermoplastic tube heater or a resistance heating element, and a first As shown in the figure, it changes linearly, as shown in Figure 2, it changes in a curved manner, and as shown in Figure 3, a limited area in the center is of equal diameter and then both ends change linearly. The difference in outer diameter between the center and both ends is determined by a pressure roller with a uniform outer diameter and a shaft. Even when the rollers are used in parallel, there is no gap in the center due to the elasticity of the surfaces of both rollers, and it is preferable to set the range to be similar to that in a conventional heat roller fixing device. For example, if the roller shaft is 330 tnm, the range of this outer diameter difference is 0.05
~0.15 fiffl is appropriate, and if the roller width changes, it can be changed in proportion to it. That is, the heat roller fixing device of the present invention uses the same fixing roller and pressure roller as in the conventional heat roller fixing device for preventing wrinkles.

In the heat roller fixing device of the present invention, as shown in FIG. 4, the fixing roller 1 and the pressure roller 2 are arranged so that their axes intersect in a projection plane parallel to the plane in which the recording paper is fed. This axis crossing can be achieved by keeping the axis of the fixing roller 1 perpendicular to the feeding direction of the recording paper and swinging the axis of the pressure roller 2.
On the other hand, it may be possible to have l1qi1 of the fixing roller 1 swing in the opposite direction, or to have both shafts swing in opposite directions, and the bearing difference angle α is the difference in the outer diameter between the center and both ends of the fixing roller It is also related to the elasticity of the surfaces of both rollers, but from 0.3 to
The range is preferably 1.5°. Bearing difference angle α is 0
．． If the angle is smaller than 3°, the recording paper may show a wavy phenomenon or wrinkles may occur when recording on both sides. If the angle still exceeds 1.5°, fixing failure may occur, especially on both edges, or the recording paper may If the moisture content has increased due to being left in the cassette for a long time, wrinkles may appear (4).
The contact pressure between fixing roller 1 and pressure roller 2 is reduced to the normal 1.5 K.
e)/am, as the contact pressure is increased, there is a tendency for fixing failure to decrease and wrinkle occurrence rate to increase.

〔Example〕

Next, specific examples of the present invention will be described.

An 870W halogen tube heater is installed penetrating the interior of the roller core made of aluminum with a wall thickness of 5 mm, and the surface of the roller core is 30 μm thick at the center and 4 mm thick at both ends.
5 μm polytetrafluoroethylene resin (PFA manufactured by DuPont)
A fixing roller 1 with an average outer diameter of 40 mm and a roller width of 336 mm, and a silicone rubber layer with a thickness of 4.5 mm on the surface of the roller core made of stainless steel with a wall thickness of 2 mm. A pressure roller 2 with an outer diameter of 40 mm and a roller width of 326 mm, on which a surface layer made of P1i'A resin with a thickness Q and 5 mg is provided, is placed 50 mm from below with respect to the fixing roller 1. The pressure roller 2 was used so as to be brought into pressure contact with a pressing force of 1, and the bearing difference angle α was variously changed to fix toner images on various types of recording paper. The surface temperature of the fixing roller 1 was 200° C., the fixing speed was 220°/5eC1, and the toner image fixing surface of the recording paper was on the fixing roller 1 side, and silicone oil was applied to the surface of the fixing roller 1 to prevent offset.

Table 1 shows the relationship between the bearing difference angle α and the wrinkle occurrence rate.

Note that the wrinkle occurrence rate in Table 1 is the result of double-sided recording, since the corrugated nail phenomenon will eventually cause wrinkles when double-sided recording is performed, and the average is based on the recording paper size and the initial recording paper in double-sided recording. A3-B5 is the average wrinkle occurrence rate that only looks at the influence of the bearing difference angle α, which includes the relationship between the feeding direction and the subsequent feeding direction, the density of the toner image, and the difference in adhesion amount. Wrinkle occurrence rate classified by size, same and opposite is the wrinkle occurrence rate classified by size, light,
Medium and dark are when the toner adhesion density is low as in the case of recording an image written in pencil, when the toner adhesion density is medium as in the record of a type print image, and when the toner adhesion density is medium as in the record of a photographic image. This is the wrinkle incidence rate classified by cases of high concentration and cases of high concentration. Regarding the fixing, ◯ indicates that fixing was performed uniformly on both sides, and △ indicates that some fixing failure occurred on both ends. And N5 is 2 to 75 5oKy pressing force of the pressure roller 2.
The results are shown when the pressing force is increased in this way, the fixing becomes good, but the occurrence rate of wrinkles increases.

As shown in Table 1, compared to the comparative example in which the N1 bearing difference angle was 00, the wrinkle occurrence rate was significantly reduced in the embodiment of the present invention in which the bearing difference was M2 to 5, and the wave peg phenomenon was observed. will also decrease.

Table 2 shows the results of measuring how the contact state of the fixing roller 1 with the recording paper changes as the bearing difference angle changes. Indicates the printing width in the recording paper feeding direction when printing is applied to recording paper, and N1 to 4 are M1 to M1 in Table 1.
This corresponds to each of the four conditions.

Table 2 Comparing the results in Tables 1 and 2, it can be seen that the wrinkle occurrence rate decreases as the difference in nip width between both ends and the center decreases, and fixing maintains a uniform and good condition as the pressure compensates for the temperature drop at both ends. However, considering that the occurrence of wrinkles increases when the fixing roller has a uniform outer diameter, it is thought that the reason for the decrease in the wrinkle occurrence rate is more complicated.

〔Effect of the invention〕

In the heat roller fixing device of the present invention, the excellent effect of reducing the occurrence of wrinkles and wave pegs on recording paper can be obtained, and the toner image can be easily and stably fixed. and,
The heat roller fixing device of the present invention is particularly suitable for recording on both sides of recording paper.

[Brief explanation of the drawing]

1 to 3 are side views showing an example of the outer shape of a fixing roller used in the present invention, and FIG. 4 is a plan view showing a bearing difference between the fixing roller and the pressure roller. 1... Fixing roller, 2... Pressure roller, α...
Bearing difference angle.

Claims (2)

[Claims] (1) A fixing roller with a built-in heater and a larger outer diameter at both ends than at the center and a pressure roller with a uniform outer diameter clamp and feed the recording paper with the toner image attached, and record the toner image. A heat roller fixing device n0 for fixing onto paper, characterized in that both rollers are mutually supported by bearings. (2) The bearing difference angle between the two rollers is 0.3° to 1.5°.
A heat roller fixing device according to claim 1 falling within the scope of claim 1.