JPH04240885A - Fixing device - Google Patents

Abstract

PURPOSE:To always steadily fix a toner picture even onto a sheet of recycled paper or thin paper by means of a heat roller by providing regulating follower rollers, whose outside diameters are greater than those of paper-ejection follower rollers, at both ends of the paper-ejection follower rollers. CONSTITUTION:The regulating follower rollers 16a and 16b, whose outside diameters are greater than those of the follower rollers 13a, 13b, 13c and 13d, are provided on both ends of a follower roller shaft 14 so that they can freely rotate. Thus, when the sheet of recording paper P is carried and ejected, both ends of the recording paper P are extended outward and struck by the regulating folower rollers 16a and 16b to be steady.

Description

[Detailed description of the invention]

0001

FIELD OF INDUSTRIAL APPLICATION The present invention relates to a fixing device applied to image forming apparatuses such as electrophotographic copying machines, laser beam printers, facsimile machines, and computer output printers, and in particular to improvements in the paper ejection section of the fixing device. It is related to.

0002

2. Description of the Related Art A heat roller fixing device for an image forming apparatus such as a copying machine is known from, for example, Japanese Patent Application Laid-Open No. 55-81378.

The fixing heat roller is a thick aluminum roller whose surface is coated with Teflon or the like, and a heating element such as an infrared lamp (halogen heater) is installed inside. Further, the circumferential surface of the heat roller is in contact with, or in a state close to, a recording paper insertion/ejection guide, a separation claw, a toner cleaning roller, and the like. The pressure roller for sandwiching and passing the recording paper between the heat roller and the heat roller is usually made of silicone rubber or a roller coated with silicone rubber. Further, a temperature sensor is installed on the circumferential surface of the heat roller to detect the surface temperature, such as a thermocouple or a thermistor. The recording paper on which the toner image has been formed is continuously inserted between a heat roller and a pressure roller, and is held and pressed while receiving heat. As a result, the toner is fused to the recording paper surface and fixed. The recording paper on which the toner has been fixed is ejected to the outside while being held between a paper ejection driving roller and a driven paper ejection driven roller, and is stored in a tray to complete copying (recording) and fixing.

[0004] In recent copying machines, efforts have been made to save space by downsizing and front loading. In order to downsize the machine, each unit device must also be downsized, and the fixing device must also respond to downsizing by reducing the diameters of the heat roller and pressure roller.

[0005]

[Problems to be Solved by the Invention] Recording paper discharged from a fixing device usually curls upwardly or downwardly depending on the type of paper, the direction in which it is set in a paper feeder, etc. In general, the curl of the recording paper tends to increase as the diameter of the heat roller and the pressure roller become smaller. In order to prevent this curling, some paper ejection rollers have a flange. However, those with a flange had problems such as scratches and marks, especially on thick recording paper. Additionally, in recent years, recycled paper has begun to be used for recording paper from the perspective of resource conservation. This recycled paper has strong hygroscopic properties, and especially in high temperature and high humidity environments, it absorbs moisture and becomes weak, has strong upward curls, and some papers curl up on the paper output tray. In this case, if the paper is passed continuously, the paper may become scattered or block the paper ejection port, causing a paper jam.

[0006]

[Means for Solving the Problems] It is an object of the present invention to eliminate these problems and to fix toner images using a heat roller fixing device that is always stable on both weak paper such as recycled paper and thin paper, and thick paper. It is an object of the present invention to provide a fixing device that performs the above operations, ejects sheets reliably, and functions safely, and also to make it possible to downsize the device.

The present invention, which achieves the above object, includes a plurality of drive rollers integrally provided on a drive rotation shaft connected to a drive source, and rotatably supported on a support shaft provided in parallel above the drive shaft. and a roller that rotates drivenly in pressure contact with the drive roller, and a fixing device that discharges the fixed paper to the outside of the machine after being in pressure contact with the rollers, the outermost one of the plurality of drive rollers; The fixing device is characterized in that a regulating driven roller having an outer diameter larger than the driven roller is provided at a position axially outermost shifted from the driving roller.

Furthermore, the present invention provides a regulating roller having an outer diameter larger than that of the driving roller, at an intermediate position between the driven roller and the regulating driven roller, and at the outermost side of the driving roller and/or in the middle of the driving roller. This is a fixing device characterized by being provided with a drive roller.

[0009]

[Example] First, an outline of the process leading up to the fixing device in a copying machine is that an image is exposed on the photoconductive surface of the charged photoreceptor drum (image carrier), and an electrostatic latent image of the original image is created. . This electrostatic latent image is developed to form a toner image, which is transferred onto transfer paper (recording paper). The recording paper onto which the toner image has been transferred is separated from the photoreceptor drum, conveyed, further thermally fixed by the heat roller fixing device according to the present invention, and then discharged outside the machine.

FIG. 1 is a sectional view of a heat roller fixing device according to the present invention. Reference numeral 1 indicates a heat roller, and a heating element 2 such as a halogen heater is disposed inside the heat roller 1. A pressure roller 4 that presses against the heat roller 1 is provided below the heat roller 1 as an opposing roller. A recording paper P having a toner image passes through the nip device between the pair of rollers 1 and 4,
By passing the toner image toward the heat roller 1 in the direction of arrow A, the toner image on the recording paper P is fixed.

The heat roller 1 is made of polytetrafluoroethylene resin (PT) with a thickness of about 30 μm on the outside of a pipe-shaped metal core.
It is a small-diameter roller coated with FE) with a wall thickness of 2 mm and an outer diameter of approximately 27.5 mm.

The heating element 2 built into the heat roller 1 is an approximately 850W heater located approximately in the center of the heat roller 1, and is designed to maintain the peripheral surface temperature of the heat roller 1 at around 200°C during copying. It's controlled. Further, reference numeral 3 denotes a cleaning roller, which cleans toner adhering to the heat roller 1 while pressing against the circumferential surface of the heat roller 1 and rotating.

The pressure roller 4 is a roller having a pipe-shaped metal core coated with a silicone resin having a thickness of 5 mm on the outside, and a perfluoroalkoxyfluoroethylene resin layer provided thereon. 1, it is pressed from directly below and rotates counterclockwise.

A recording paper P, on which a toner image has been transferred, is moved toward the pressure contact portion between the heat roller 1 and the pressure roller 4, and
It is carried in in the direction of arrow A under the guidance of insertion guide members 5A and 5B. The recording paper P is held between the pressure contact portions of the rollers 1 and 4 and conveyed in the direction of arrow B. At this time, the recording paper P
The upper toner is heated by a heating element 2 built into the heat roller 1.
It is melted by the amount of heat generated and fixed on the recording paper P. The recording paper on which the toner image has been fixed is carried out from the pressure contact portion of both the rollers 1 and 4, and is peeled off from the circumferential surface of both rollers by the separating claw 6. ) and a plurality of paper discharge driven rollers 13 (hereinafter referred to as driven rollers), the sheet is conveyed while being held therebetween, and is discharged in the direction of arrow B (outward).

FIGS. 2 and 3 are side sectional views showing the paper ejection mechanism of the fixing device. First, the basic mechanism of conventional paper ejection will be explained with reference to FIG. The drive rotation shaft 11 has a length that matches the maximum width of the recording paper P to be used, and a drive roller is installed at a position corresponding to the various paper widths of the recording paper P to be used (for example, A3 size, B4 size, A4 size, B5 size). 12a, 12b, 12c, 1
2d is installed and drives and rotates integrally with the drive rotation shaft 11. And these drive rollers 12a, 12b, 12c
, 12d are provided with corresponding driven rollers 13a.
, 13b, 13c, and 13d are attached so that they can rotate freely around two driven roller shafts (support shafts) 14a and 14b, respectively, as rotating shafts. The number of drive rollers 12 and driven rollers 13 is determined depending on the type of recording paper size to be used. Each driven roller 13a, 13b, 13c, 1
3d rotates as a result of the rotation of the drive roller, so the driven roller shafts 14a and 14b are able to swing up and down to some extent and are pressed against the drive roller 12 by a spring.

The recording paper P is driven by drive rollers 12a, 12b, 1
2c, 12d and driven rollers 13a, 13b, 13c, 1
While being held between 3d and driven by the drive roller,
Basically, the paper is conveyed and ejected from the bottom surface to the top surface in the vertical direction in FIG. 3 while maintaining a flat surface. These drive rollers 12 are made of rubber and are molded integrally with the drive roller shaft 11, and the driven rollers are made of polyacetal resin, nylon resin (polyamide), or the like.

In general, the basic mechanism for ejecting paper from a fixing device is as described above, but this has the problem that curling becomes large when a small-diameter heat roller or pressure roller is used, as described above. Therefore, as shown in FIG. 2, at both ends of the driven roller shaft 14, that is, at positions corresponding to both ends of the width of the recording paper, an outer diameter (for example Regulation driven rollers 16a and 16b with a diameter of 1 to 5 mm are provided in a freely rotatable state. The regulation driven rollers 16a, 16b are made of a resin material with a small coefficient of friction such as polyacetal resin (POM) or polyamide resin (PA), and the outer diameter corners of the rollers have a small spherical shape. As a result, when the recording paper P is conveyed and ejected, both ends of the recording paper P are stretched outward by the regulation driven rollers 16a and 16b and are undulated, which has the effect of strengthening the stiffness of the recording paper P. can bring about

Furthermore, a driven roller 13a on the drive roller side,
Drive rollers 12a, 12b, 12c, which are installed on the drive rotation shaft 11 opposite to 13b, 13c, 13d,
The drive roller 12 is located at an intermediate position between the positions of the drive rollers 12d and 12d.
Regulating drive rollers 15a, 15b, 15c, and 15d having an outer diameter larger than the outer diameter of rollers a, 12b, 12c, and 12d are formed integrally with the drive rotation shaft 11 and installed to rotate. By doing this, the recording paper P being conveyed and discharged passes while being curled in a waveform in a direction parallel to the traveling direction. Therefore, it has the effect of canceling out the curling force in the direction perpendicular to the traveling direction when pressed by the heat roller 1 and the pressure roller 4, so it is possible to prevent the recording paper from curling on the paper output tray and to recycle it. Paper can also be ejected without causing paper ejection failure. All of these regulating rollers can be made using conventional materials and processing methods.

[0019]

Effects of the Invention As described above, the heat roller fixing device of the present invention makes it possible to suppress curling of recording paper even when the diameters of the heat roller and pressure roller are reduced.
In addition, conventionally, when using weak recording paper such as recycled paper,
The problem of recording paper being scattered all over the paper output tray can now be avoided. Furthermore, even when thick recording paper is used, problems such as scratches on the recording paper, which occur when a flange is attached to the roller, have been solved. These mechanisms can be constructed at low cost using conventional technology.
It is now possible to provide a fixing device that always has a reliable paper ejecting function, and it has also become possible to downsize the device.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the configuration of a fixing device according to the present invention.

FIG. 2 is a side cross-sectional view showing a paper ejection roller portion of the fixing device.

FIG. 3 is a side cross-sectional view showing the basic mechanism of a paper ejection roller portion of the fixing device.

[Explanation of symbols]

1...Heat roller
2...Heating element 3...Cleaning roller
4...Pressure rollers 5A, 5B...Insertion guide 6...Separation claw 11...
Drive rotation shafts 12a, 12b, 12c, 12d... Paper discharge drive rollers (drive rollers) 13a, 13b, 13c, 13d... Paper discharge driven rollers (driven rollers) 14a, 14b... Driven roller shafts (
Support shaft) 15a, 15b, 15c, 15d...Regulation drive roller 16a, 16b...Regulation driven roller P...Recording paper

Claims (2)

[Claims] 1. A plurality of drive rollers integrally provided on a drive rotation shaft connected to a drive source, rotatably supported by a support shaft provided in parallel above the drive shaft, and in pressure contact with the drive roller. In the fixing device, the fixing device is provided with a roller that rotates driven by the rollers, and the fixed paper is pressed against the rollers and discharged to the outside of the machine. A fixing device characterized in that a regulation driven roller having an outer diameter larger than the driven roller is rotatably provided on the support shaft at a position shifted from the other side. 2. A regulation drive roller having an outer diameter larger than that of the drive roller is provided at an intermediate position between the driven roller and the regulation driven roller, at the outermost side of the drive roller and/or between the drive rollers. The fixing device according to claim 1, wherein the fixing device is provided on the drive shaft.