JPS60104980A - Fixing device - Google Patents

Abstract

PURPOSE:To prevent the generation of paper wrinkles and uneven fixing by constituting one cut of two rollers supporting a belt contacting with one roller of a heat/compression fixing device by a specific shape. CONSTITUTION:The belt 11 contacting with a heating roller 14 is wound around a straight roller 12 of which diameter is not changed in the axial direction and a drum type roller 13 in which the center diameter of the axis is larger than the diameter of a side end part. If tension is applied to the belt 20(11), the belt 20 having width L is expanded by l in the width direction and generates drum type deformation narrowing its width at the center part and twisted stripes are generated on the surface of the belt 20. However, the generation of the twisted stripes are prevented by using the drum type roller 13, so that the generation of paper wrinkles and uneven fixing is prevented.

Description

Detailed Description of the Invention: Industrial Field of Application The present invention is applicable to) 7. Compressing and heating unfixed toner powder on an image carrier (recording paper) in an information recording device such as a printer, copier, or printer. This applies to the heat compression 4 fixing device that fixes the image.

Conventional Structures and Problems With the remarkable development of information recording devices in recent years, the demand for improved image quality of recorded matter has increased, and it has become necessary to fix stable and high-quality toner powder. A conventional fixing device will be described below with reference to the drawings. FIG. 1 is a side sectional view of a conventional fixing device, in which 1 is an endless belt made of rubber, cloth, or a composite material of these;
This endless belt 1 is supported by support rollers 2.3 so as to be freely wound. A heating roller 4 is composed of a surface treatment layer 5, a roller base material 6, and a heater 7. Here, the roller base material 6 is generally made of a metal material such as aluminum, and the surface treatment layer 5 is made of a material with good mold releasability such as a fluoride resin in order to improve peeling from the toner powder 8. It is formed by coating the roller base material 6. The heater 7° is constituted by a halogen lamp or the like, and controls the surface temperature of the heating roller 4 to a predetermined temperature by a control circuit. The endless belt 1 and the heating roller 4 are in contact with each other with a predetermined pressure applied between their axes by a spring or the like. Further, the heating roller 4 is driven and rotated at a predetermined speed by an external drive source (not shown), and the endless belt 1 is rotated in a direction opposite to the heating roller 4 due to vl and vibration force due to contact with the heating roller 4. Driven in the rotational direction.

In this state, when the recording paper 9 holding the toner powder 8 is applied to the contact portion between the endless bells 1 to 1 and the heating roller 4 (hereinafter referred to as the nip portion 10), the toner powder 8 is transferred to the nip portion. While passing through the paper 10 , it is melted by pressure and heat and fixed on the recording paper 9 .

The structure of the conventional fixing device described above is relatively simple, and the nip width is larger than when fixing by passing recording paper between the rollers! ] (It has the advantage of being able to take a longer time for fixing and being able to be fixed at a constant temperature with a small pressure and a low constant temperature, but due to twisting and wrinkles of the belt that occur when the belt is fed However, there are problems in that wrinkles and uneven fixing occur on the recording paper after one loaf.

Purpose of the Invention The present invention solves the above-mentioned conventional drawbacks by eliminating the twisting of the belt surface that occurs when the belt runs.
It is an object of the present invention to provide a fixing device that eliminates creases in recording paper and uneven fixing caused by twisting of a bell 1- during fixing.

Structure of the Invention In order to achieve the above-mentioned object, the fixing device of the present invention includes a belt that is supported so as to be wound around at least two wooden supporting rows, and a roller that is in pressure contact with the belt. At least one of the belts or rollers is heated, and the toner powder is passed through the image carrier holding the toner powder in the pressure contact portion, and the toner powder is heated and compressed to melt it on the image carrier. At least one of the support rollers is a drum-shaped roller having a diameter larger at the center than at the ends.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 shows a side sectional view of a fixing device according to an embodiment of the present invention. Reference numeral 11 denotes an endless bell I- made of silicone rubber, cloth, or a composite material of the two countries, which includes a straight roller 12 whose diameter does not change in the axial direction and a drum-shaped roller whose diameter at the center of the shaft is larger than the diameter at the side ends. 13 so that it can be wound freely. A heating roller 14 is composed of a surface treatment layer 15, a roller base material 16, and a heater 17. The surface treatment His is made of a material such as fluoride resin or silicone rubber that is heat resistant and has good releasability from the toner powder 18 held on the recording paper 19, and the roller base material 16 is made of a material that has the strength of the heating roller 14. It is the central part and is generally made of a metal material such as aluminum. The heater 17 is a heat source for heating the heating roller 14, and the heating roller 14 is controlled by a control circuit (not shown).
The outer periphery of the opening is controlled to a predetermined degree and heated.

Next, how belt torsion is resolved by using a drum-shaped O-la will be explained in comparison with a conventional example.

FIG. 3 is a model diagram showing how the belt deforms when it is placed on two rollers.

In the figure, the two-dot chain lines 19a to 19i are imaginary lines for clarifying the state of deformation of the belt.

Figure 3a shows the case where no tension is applied to the bells 1 to 20, and the third diagram shows the case where both end faces in the tension direction are restrained so as not to be deformed from the state of figure a and tension is applied.

As you can see from the drawing, the belt 20 width is L1 bell 1 ~
If the elongation n) of the belt 20 as a whole is ρ, looking at the change in the elongation of the belt 20 in the width direction using the virtual line, the elongation of the center portion 19e of the belt 20 is ρ, but the elongation of the belt 1-20 in the center is ρ. As the width narrows at the end, the imaginary line undergoes a bow-like deformation that extends toward the center as it approaches the end, and the two-dot chain 1i! The amount of deformation of 19a and 1'li is larger than the amount of deformation ρ at the center. Actually Bell 1-2
0 is kicked when tension is applied between the two [1-R], and the belt is deformed at the contact part between the belt and the roller due to the frictional force between the rollers 1 and 1. Since the belt is restrained, the deformation of the belt between the rollers is
The belt undergoes the same deformation as explained using the model in Figure 2. When the belt is stretched between rollers with tension, the circumference of a straight pair of rollers increases in the width direction of the belt from the center to the ends. To increase.

FIGS. 4a and 4b show a belt drive unit comprising a belt and a belt support roller in the conventional example shown in FIG. 1 and the embodiment shown in FIG. 2, respectively. As shown in FIG. 4, in the present invention, a drum-shaped roller 13 is used, which forcibly stretches the circumference of the endless belt 11 at the center in the width direction. The circumferences are equal.

Next, using FIGS. 5a and 5b, the operation of the belt in the conventional example shown in FIG. 1 and the embodiment shown in FIG. 2 when the belt is driven in pressure contact with a heated [1-ra] will be explained. Figure 5a
In the case of the conventional example shown in , the circumferential length of the endless belt 1-1 changes, so when the endless belt 1 is driven at a constant circumferential speed while in pressure contact with the heating roller, the center part with the short circumference changes. Lead from the long end. endless belt 1
An imaginary line 2 perpendicular to the rotation direction that was placed before the rotation
1 is a straight line in the state shown in ■ just before rotation, but when it starts rotating in the direction of the arrow, as the number of rotations increases, the circumferential length difference J: An operation in which the center part of Liberto 1 precedes the end parts. gradually progresses. Therefore, if the belt 1 continues to rotate as it is, it is possible that the belt 1 will be twisted and damaged between the center and the ends, but in general, the deformation recovery force of the material and the torsional force caused by the difference in circumference are balanced. The lead in the center stops when it reaches (1). However, the belt twisted in this way
An uneven twisted line 22 as shown in ■ appears. This twisted line 22 occurs when the recording paper is passed through and fixed while the heating roller and the bells 1 to 1 are in pressure contact with each other, causing uneven pressure at the contact area, which causes paper wrinkles and uneven fixing. In the case of the embodiment of the present invention shown in the figure, one of the two rollers is a straight roller 12 and the other one is a drum-shaped roller 13. By setting the width to the maximum width, the difference in circumference in the width direction of the belts 1 to 1 can be covered by the phase f2.If the difference in circumference in the width direction of the belt 11 is set constant in this way, as shown in FIG. As shown in (I) before the belt rotation and (2) during the belt rotation, the leading 46 portions disappear between the center and end of the belt, so the imaginary line 23 perpendicular to the rotation direction shows that the belt 11 is rotating. The belt 11 is not deformed and is kept substantially straight.Therefore, there is no twisting of the belt 11 surface, and no paper wrinkles or uneven fixing occur during fixing.

In the embodiment shown in FIG. 2, the circumferential length difference in the width direction of the belt that occurs when a belt with no circumferential length difference in the width direction is placed on two straight rollers without deformation is calculated by one tree [-1]. −
Although the case where the rollers are drum-shaped and offset is shown, it is also possible to make both of the two rollers drum-shaped. Further, the number of rollers supporting the belt is not limited to two, and it is also possible to use several rollers. Furthermore, although the heating roller 14 is heated by the heater 17 in the above embodiment, it is also possible to heat the endless belt 11 side, or it is also possible to heat both the heating roller 14 and the endless belt 11.

Effects of the Invention As described above, the present invention includes a belt that is supported so as to be wound around at least two supporting rollers, and a roller that is in pressure contact with the belt, and at least one of the belt or the roller is heated. In this state, an image carrier j'j holding powder 1 to 1 is passed through the pressure contact part, and the toner powder is heated and compressed to melt and fix it on the image carrier. At least one of the support rollers is a drum-shaped roller with a diameter larger at the center than at the ends, so that the belt is supported by a straight roller so that it can be wound freely under tension. It is possible to cancel out the difference in the elongation of the belt which occurs in the width direction of the belt 1-, and by keeping the circumference of the belt constant in the belt width direction, twisting lines can be prevented from occurring in the belt. Accordingly, it is possible to realize a fixing device that eliminates paper wrinkles on the image carrier and uneven fixing that occur during fixing.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of a conventional fixing device, FIG. 2 is a side sectional view of a fixing device according to an embodiment of the present invention, and FIG. 3 a, 1)
31 is a clear view of belt deformation, FIGS. 4a and b are enlarged views of main parts of the conventional example of FIG. 1 and the embodiment of the present invention, and FIGS. 5a and b
1 is an explanatory diagram of the operation of the belt of the conventional example and the embodiment of the present invention shown in FIG. 11... Endless belt 12... Straight roller, 13... Drum-shaped roller, 14... Heating 0-ra, 18... Toner powder, 19... Recording paper agent Yoshihiro Morimoto

Claims (1)

[Claims] 1. It has a belt supported so as to be wound around at least two support rollers, and a roller that presses against the belt 1, and the press-contact is carried out in a state where at least one of the belt or the roller is heated. The toner powder is heated and compressed to be melted and fixed on the image carrier by passing through the vjA carrier holding the toner powder in the support O-
At least one of the rollers is a drum-shaped fixing device in which the diameter of the central portion is larger than the diameter of the end portions.