JPH10254275A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of transporting quality such as wavy wrinkles or wear of an image during transportation, by providing a transfer paper guide roll for preventing the skirt bent of a transfer paper on the paper discharge section from a nip part between a fixing roller and a pressure roller. SOLUTION: In this fixing device, the transfer paper guide roll 23 is installed in the rotary direction of a supporting member 22 mounted on a bracket 21, and the supporting member 22 is composed of a base stock having spring property. The transfer paper subjected to the image fixing in the nip part between rollers 1 and 2 is put on the transfer paper guide roll 23 and transported toward discharging rollers pair 8 while rotating the roll. In such a manner, the occurrence of wavy wrinkles is prevented, and moreover, at the time of both sides copying, the occurrence of a jamming originated by toner of a rear side, sticking to the guide is prevented. Then, even if the jamming occurs, since supporting member 22 is composed of a base stock having spring property, the transfer paper guide roll 23 is shifted by temperature deformation, however returns to the home position thereafter, hence the occurrence of plastic deformation is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for fixing an unfixed image formed on a transfer sheet with a fixing roller and a pressure roller which is in pressure contact with the fixing roller.

[0002]

2. Description of the Related Art FIG. 8 shows a typical example of a conventional fixing device of this type. This fixing device includes a fixing roller 1 having a heating member 3 provided therein.
And a pressure roller 2 that comes into pressure contact with the fixing roller 1. Normally, the fixing roller 1 is a rigid roller having a metal core and a release layer formed on the surface thereof, while the pressure roller 2 is composed of a metal core and a heat-resistant elastic release formed on the surface thereof. And an elastic roller having a layer.
The upper and lower peeling claws 4 and 5 and the upper and lower guide plates 6 and 7 are provided behind the nip portion between the rollers 1 and 2.

In such a device, the transfer paper 9 is heated and pressed at its nip by the fixing roller 1 composed of a rigid roller and the pressure roller 2 composed of an elastic roller. After passing through the nip portion, the sheet curls toward the fixing roller 1 and bends upward following the surface of the fixing roller 1. When the degree of this curvature increases, the sheet falls onto the lower guide plate 7 due to its own weight and breaks down. Such a problem occurs when the transfer paper 9 is conveyed to the pair of paper discharge rollers 8 so that the transfer paper 9 is periodically performed to form wrinkles having waves as shown in FIG.

Such wrinkles are caused by the difference in the image ratio of the unfixed image on the transfer paper 9 due to the difference between the two rollers 1 and 2 of the transfer paper 9.
It also occurs due to the difference in the state of discharge and conveyance from the nip portion of No. 2. That is, when the image ratio is low, the transfer paper 9 is discharged in the tangential direction of the nip portion because the toner amount on the transfer paper 9 is small and the releasability from the fixing roller 1 is good. Is high, the amount of toner on the transfer paper 9 is large, so that the releasability from the fixing roller 1 is reduced, and the paper is wound around the fixing roller 1 and conveyed. By the way, one transfer paper usually has a high image ratio,
The transfer paper immediately after passing through the nip portion is wrapped around or separated from the fixing roller 1 so that the transfer paper 9 moves up and down, and wrinkles are formed by this movement. Problem.

[0005]

In order to solve such a problem, a device as shown in FIG. 10 has been proposed. The device shown in FIG. The guide ribs 12 are arranged. Such a copying machine is effective in preventing the formation of wrinkles. However, recently, an increasing number of copying machines have been provided with a copying machine for performing double-sided copying. There is also a fixed image on the back side, and the softened toner image of this fixed image
13 rubs against the guide ribs 12 and disturbs the image.

Generally, the discharge speed of the discharge roller pair 8 is set to be higher than the speed of the transfer paper 9 at the nip in order to apply tension to the transfer paper 9 and prevent wrinkles from being formed. The effect of preventing wrinkle formation does not occur until the leading end of the transfer paper 9 is held by the discharge roller pair 8, and the back surface of the transfer paper 9 is strongly pressed by the guide ribs 12 due to the tension applied to the transfer paper 9. Therefore, in addition to the disturbance of the image, there is a problem that the leading end of the transfer paper 9 being conveyed by the toner adhered to the guide ribs 12 is caught and a jam occurs.

[0007] Separately, Japanese Patent Application Laid-Open No.
A fixing device disclosed in Japanese Patent Publication No. 794 has been proposed. Incidentally, in the above-described double-sided copying machine, in order to make the whole compact, a double-sided device for double-sided copying is often arranged below the image forming apparatus including the fixing device. In such a case, in this fixing device, the guide member that guides the transfer paper immediately after fixing extends substantially along the fixing roller and conveys the transfer paper upward, so that the fixing device is extremely inverted. As a result, there is a problem that the transport quality is impaired.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the conventional fixing device, and to prevent the formation of wrinkles with waves during the transfer of the transfer sheet after the fixing operation. When used for transfer, the back side of the transfer paper rubs against the guide, and the image on the back side is rubbed, and the toner on the back side adheres to the guide etc. An object of the present invention is to provide a fixing device that does not impair the quality.

[0009]

According to the present invention, in order to achieve the above object, the invention according to claim 1 comprises a fixing roller and a pressure roller which presses and contacts the fixing roller. In the fixing device, a transfer paper guide roll for preventing the transfer paper from being bent is provided at a paper discharge portion from a nip portion of both rollers.

According to a second aspect of the present invention, in the first aspect of the present invention, the transfer paper guide roll is provided on a peeling claw provided on the pressure roller side.

[0011] The invention described in claim 3 is the invention according to claim 1 or 2.
Wherein the transfer paper guide roll has a release layer such as PFA or PTFE on the surface.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the embodiments of the present invention shown in the drawings, the same parts as those in the above-mentioned conventional example are denoted by the same reference numerals, and the description thereof will be omitted. The description is omitted, and only different parts will be described.
In the first embodiment of the present invention shown in FIGS. 1 to 3, the fixing roller 1 has a core metal made of aluminum, and a release layer made of PFA or PTEE is formed on the surface of the core metal. The member 3 is constituted by a halogen heater or a nichrome wire heater. Further, a temperature detecting means 15 composed of a thermistor for detecting the temperature of the surface is provided.

The pressure roller 2 is provided with a heat-resistant rubber layer made of silicone rubber on the outer periphery of a cored bar.
A PFA tube with good release properties is covered. Bearings 16 are mounted on both ends of the shaft of the pressure roller 2, and the bearing 16 is supported by a pressure lever 17, and the base end of the pressure lever 17 is supported on a machine frame (not shown) by a pivot 18. The free end is connected to the other end of a spring 19, one end of which is also attached to the machine frame. The spring 19 presses the pressure roller 2 against the fixing roller 1.

As shown in FIG. 2, a bracket 21 is mounted on the machine frame, and a transfer paper guide roll 23 is rotatably mounted on a support member 22 mounted on the bracket 21 in parallel with the lower release claw 5. The support member 22 is, for example, SUS301
-Made of a springy material such as CPS-3 / 4H. Transfer paper guide roll 23 in this embodiment
Is made of polyacetal or a resin obtained by adding a fluororesin to polyacetal.

In this embodiment, the transfer sheet on which the image is fixed at the nip portion between the rollers 1 and 2 is mounted on the transfer sheet guide roll 23 and is conveyed toward the discharge roller pair 8 while rotating it. This eliminates wrinkles and wrinkles, rubs the image on the back side of the transfer paper during double-sided copying, or causes toner on the back side to adhere to guides and the like, causing jams due to dirt. Even if a jam occurs, the transfer paper guide roll 23 is temporarily deformed and displaced because the support member 22 is made of a springy material. It is prevented from returning and being plastically deformed.

In this embodiment, as shown in FIG. 3, a straight line BB extending at right angles to a straight line AA connecting the centers of the fixing roller 1 and the pressure roller 2, The angle θ between the tangent C to the paper guide roll 23 and the tangent C is 10
If it is more than °, the waving phenomenon could be eliminated,
When the angle is 13 ° or more, jamming occurs with transfer paper having a weak stiffness, and it is preferable to set the angle to 11.5 ± 1.5 °.

FIGS. 4 and 5 show a second embodiment of the present invention. This embodiment is different from the first embodiment in that a lower peeling claw 5 is provided along with a transfer paper guide roll 23. Is not different from the first embodiment. Due to the above difference, the leading end of the transfer paper to be wound around the pressure roller 2 is surely picked up by the lower peeling claw 5 and guided to the transfer paper guide roll 23 to improve the transport quality. .

FIG. 6 shows a structure of a support portion of a transfer paper guide roll 23 according to a third embodiment of the present invention. In this embodiment, the transfer paper guide roll 23 is provided with a lower peeling claw 5.
The second embodiment is different from the second embodiment in that the second embodiment is supported by the pivot 24, and there is no difference in the other configuration from the second embodiment. And the above difference makes the structure simple and easy to manufacture.

FIG. 7 shows the structure of a transfer paper guide roll 23 according to a fourth embodiment of the present invention. In this embodiment, the transfer paper guide roll 23 according to the first embodiment is shown.
Is provided with a release layer 26 such as PFA or PTFE on the surface thereof, and other configurations are not different from those of the first embodiment. As a result, the toner hardly adheres to the surface of the transfer paper guide roll 23, and the durability is improved.

[0020]

According to the first aspect of the present invention, there is provided a fixing device having a fixing roller and a pressure roller which is in pressure contact with the fixing roller. A transfer paper guide roll is provided in the paper discharge section to prevent buckling of the transfer paper, so that wrinkles that form waves during transfer after the fixing operation of the transfer paper are not formed, can be used for double-sided devices. When the back side of the transfer paper is rubbed against the guide, the image on the back side is rubbed, and the toner on the back side adheres to the guide, etc. There is an effect that it is not damaged.

According to a second aspect of the present invention, in the first aspect of the present invention, since the transfer paper guide roll is provided on a peeling claw provided on the pressure roller side, the transfer paper guide roll is wound around the pressure roller. The leading edge of the transfer paper is surely picked up by the lower peeling claw and guided to the transfer paper guide roll to improve the transport quality and to have a simple structure.

The invention described in claim 3 is the first or second invention.
In the invention described in (1), since the transfer paper guide roll has a release layer such as PFA or PTFE on the surface, toner is less likely to adhere to the surface of the transfer paper guide roll, and the durability is improved.

[Brief description of the drawings]

FIG. 1 is a front view of a main part of a first embodiment of the present invention.

FIG. 2 is a perspective view of a main part of the above.

FIG. 3 is a layout diagram of a fixing roller, a pressure roller, and a guide roller according to the first embodiment.

FIG. 4 is a front view of a main part according to a second embodiment of the present invention.

FIG. 5 is a perspective view of a main part of the above.

FIG. 6 is a perspective view of a main part according to a third embodiment of the present invention.

FIG. 7 is a perspective view of a main part of a guide roll according to a fourth embodiment of the present invention.

FIG. 8 is a schematic front view of an example of a conventional fixing device of the same type as the present invention.

FIG. 9 is a perspective view showing a state of wrinkles generated by the above.

FIG. 10 is a schematic front view of another example of a conventional fixing device of the same type as the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Fixing roller 2 Pressure roller 3 Heating member 4 Upper peeling claw 5 Lower peeling claw 6 Upper guide plate 7 Lower guide plate 8 Discharge roller pair 9 Transfer paper 16 Bearing 17 Pressure lever 18 Axis 19 Spring 21 Bracket 22 Support member 23 Transfer paper guide roll 24 Axis 26 Release layer

Claims (3)

[Claims] In a fixing device having a fixing roller and a pressure roller which is in pressure contact with the fixing roller, a transfer paper guide roll for preventing the transfer paper from being bent at a paper discharge portion from a nip portion of both rollers. A fixing device characterized by being provided. 2. The fixing device according to claim 1, wherein the transfer paper guide roll is provided on a peeling claw provided on the pressure roller side. 3. The fixing device according to claim 1, wherein the transfer paper guide roll has a release layer such as PFA or PTFE on a surface thereof.