JPH04305675A - Thermal fixing device - Google Patents

Abstract

PURPOSE:To prevent deviation of an endless belt without utilizing alignment control of a driving pulley and to carry out fixing at a low cost and with prolonged service life by using a metallic endless belt and the driving pulley provided, with a guide on its edge to drive this belt, in the thermal fixing device utilizing the endless belt. CONSTITUTION:The metallic endless belt 1 is hung between the driving pulley 2 and a heat generating resistor 3. It is driven in the carrying direction of paper 5 while being abraded and slid against the exothermic resistor 3 by rotation of the driving pulley 2 and a back up roll 4. A guide 2 is provided on both edge parts of the pulley 2 so that the width of the endless belt is matched. Thus, the running safety of the metallic endless belt 1 is realized.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat fixing device, and more particularly to the structure of a heat fixing device using a heating resistor and an endless belt.

0002

[Prior Art] A conventional device is disclosed in Japanese Patent Application Laid-Open No. 49-36342.
As described in the above publication, an endless belt is wound around a pulley, and the endless belt presses a sheet of paper to which toner is attached against a heating roller.

[0003] Furthermore, the endless belts described in JP-A No. 2-157880 and JP-A No. 2-157883 are made of polyimide, polyetherimide, PES, PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether). A single layer film of heat-resistant resin such as copolymer resin) or a composite layer film, e.g.
PTFE (4 mm) on at least the image contact side of the m-thick film.
Using a fluororesin such as fluorinated ethylene resin (fluorinated ethylene resin) or PFA with a 10 μm thick releasable coating layer added with a conductive material, a heat generating resistor is placed on the inner peripheral surface of the endless belt to release the toner. The paper that was stuck was pressed against the roller. In order to stabilize the running of the endless belt, pulley alignment control has been performed.

0004

[Problems to be Solved by the Invention] The above conventional technology uses a resin material as the endless belt, so its strength against frictional sliding is low. It is not possible to prevent the endless belt from meandering by providing a guide such as a flange at the end of the endless belt and sliding the end of the endless belt against this guide, which is costly due to the drive pulley alignment. Additionally, this alignment control causes plastic deformation at the side ends of the endless belt, which poses a major problem in terms of cost reduction and long life.

[0005] Furthermore, since the above resin material has a low thermal conductivity,
In order to apply the heat from the heating resistor to the unfixed toner on the paper via the endless belt, the thickness of the resin material must be made as thin as possible, while at the same time maintaining its strength for alignment control. There were two contradictory and difficult problems.

[0006] The present invention achieves running stability such as unevenness of an endless belt at a low cost, and also extends the life of the endless belt, thereby realizing an electrophotographic apparatus with good fixing characteristics at a low cost. The purpose of the present invention is to provide a heat fixing device for

[0007]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a heating resistor, an endless belt disposed to cover the heating resistor, a drive pulley for driving the endless belt, In the heat fixing device having a backup roller that presses the paper against the heating resistor through the endless belt, the endless belt is a metallic endless belt having a fluororesin layer on the surface that contacts the paper. This is a characteristic feature.

Further, the width of the endless belt is made larger than the width of the backup roller, and the drive pulley is provided with guides for guiding both ends of the endless belt, and the drive pulley has a linearly tapered shape. The drive pulley has a shape in which the pulley diameter becomes smaller in the axial direction, and a guide for guiding the side end of the endless belt is provided at the end of the pulley with the smaller diameter, and the drive pulley has a shape in which the extension line of the axis line is A guide is provided to be inclined so as to intersect at a certain point with an extension line of the axis of the backup roller, and is provided at an end of the drive pulley near the backup roller to guide a side end of the endless belt, and the guide is The endless belt is tiltable and rotatable with respect to the axis of the drive pulley, and the drive pulley has sprockets at both ends thereof, and feed holes that engage with the sprockets are provided at both ends of the endless belt. Means having a large friction coefficient may be provided at the contact portion between the drive pulley and the endless belt, and the backup roller may have an inverted crown shape with a reduced diameter at the center.

[0009]

[Function] According to the above structure, the endless metal belt can be run by a drive pulley provided with a guide such as a flange or sprocket at the side end so as to match the width of the endless belt. As a result, the endless belt does not become lopsided, and
A metal endless belt can have sufficient strength as a belt even if it is made thin. Therefore, it runs stably for a long period of time and does not malfunction. Further, by making the width of the endless belt larger than the width of the backup roller for pressing the paper against the heating resistor via the endless belt, damage to the backup roller by the end of the endless belt can be prevented. This allows it to run stably for long periods of time.

[0010] In this way, by using a metal endless belt, the life of the endless belt can be extended, and by providing a flange, sprocket, etc. on the drive pulley for driving the endless belt, the complexity of the drive pulley can be reduced. It is possible to stabilize the running of the endless belt with a simple configuration without using detailed alignment control.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Several embodiments of the present invention will be described below with reference to the drawings. An example in which the present invention is implemented in an electrophotographic apparatus is shown in FIG. The sheets 5 accumulated in the hopper are separated and fed one by one and conveyed to the bending guide A11. The paper 5 is transported by the transport roller A9 to a transfer section where the toner on the photosensitive drum 15 is transferred. The toner image on the photosensitive drum 15 is visualized by a developing device 16. Thereafter, the paper 5 is conveyed to a fixing device 14 consisting of a metal endless belt, for example a steel belt 1, a drive pulley 2, a heating resistor 3, and a backup roller 4, and the toner image is transferred to the
It will be fixed to. After the fixation, the paper 5 is sent to the bending guide B12 via the conveyance roller B13, and then carried out to the output tray by the carry-out roller 10. The fixing device 14 is fixed to a side plate (not shown), and is arranged on the paper conveyance path after the transfer section.

FIG. 2 shows the configuration of the fixing device 14. The operation will be explained below.

The paper 5 is fed in the direction of arrow A and passed between the steel belt 1 and the backup roller 4. The steel belt 1 is sufficiently thin so that the heat of the heating resistor 3 is instantaneously transferred to the toner and the paper 5, and the surface that contacts the paper 5 is coated with a fluororesin layer. Furthermore, in order to prevent the backup roller 4 from being damaged by the end of the steel belt 1, the width of the steel belt 1 is made larger than the width of the backup roller 4, and the rigid steel belt 1 is
The end of the roller 4 does not come into contact with the soft surface of the backup roller 4.

The steel belt 1 is moved by a drive pulley 2 having a flange at its side end so as to match the width of the steel belt, and rotates in the same direction (arrow B) as the conveyance direction of the paper 5. The drive pulley 2 is rotated by a motor 6 attached to a side plate (not shown). The shape of the backup roller 4 is an inverted crown shape to prevent the paper from wrinkling.

The steel belt 1 is stretched between a drive pulley 2 and a heat generating resistor 3, and the tension acting on the steel belt 1 is determined by the distance between the drive pulley 2 and the heat generating resistor 3. The surface of the heating resistor 3 or the back surface of the steel belt 1 is treated to reduce slip resistance. A backup roller 4 is pressed against the heat generating resistor 3 via the steel belt 1, and the toner is fixed onto the paper 5 by the heat from the heat generating resistor 3.

The backup roller 4 is connected to the transmission gears 7a to 7.
It is rotated by the motor 6 via d. Transmission gear 7a~
The reduction ratio 7d is determined so that the circumferential speeds of the steel belt 1 and the backup roller 4 are the same. Note that a timing belt or a separate motor may be used to reduce the speed of the transmission gears 7a to 7d.

The heating resistor 3 may be controlled to a predetermined fixing temperature by a temperature control device using a temperature detector such as a thermistor sensor, as shown in FIG. The temperature may be controlled using a thermistor heater that can control the temperature.

FIG. 4 shows a sectional view of the steel belt 1. The steel belt 1 has a thickness of several tens of microns and has excellent thermal conductivity and durability, and its surface is primed or etched to coat it with heat-resistant and abrasion-resistant fluorine-containing materials such as PFA and PTFE. The resin layer 1a is provided with a thickness of 10 μm.

FIG. 5 shows the shape of a drive pulley 2 that drives a metal endless belt (steel belt 1). In order to prevent the steel belt 1 from meandering, the pulley 2a is provided with flanges at both ends of the drive pulley 2 so as to match the width of the steel belt 1.

In addition, the pulley 2b has a linearly tapered shape in which the diameter of the drive pulley decreases in the axial direction, so that the belt is forcibly shifted to one end of the drive pulley.
Furthermore, a flange is provided at the end where the belt is biased, for example, the larger end. When a belt is conveyed by a tapered pulley, the belt is inevitably biased to one side due to the relationship between the belt's rigidity, tension, and frictional force with the drive pulley. Generally, when the pulley is tapered and the frictional force between the belt and the pulley is large, the belt moves toward the side where the tension acting on the belt is larger, that is, the pulley diameter is larger, and the rigidity of the belt is large and the friction between the belt and the pulley is large. When the force is small, the belt moves toward the smaller pulley diameter.

The pulley 2c has a rubber layer 17 partially applied to the surface of the drive pulley that comes into contact with the paper in order to prevent the drive pulley and the endless metal belt from slipping. This rubber layer 17 may be present on the entire surface of the drive pulley. In addition, by changing the thickness of the rubber layer 17 so that it is thicker at the center than at the ends of the drive pulley and by providing a crown on the drive pulley 2, slipping between the drive pulley 2 and the metallic endless belt 1 is prevented. Not only can this be prevented, but also the meandering of the metal endless belt 1 can be prevented. Further, in addition to the rubber layer, knurling treatment may be applied to create minute irregularities on the surface.

The pulley 2d is provided with sprockets at both ends of the drive pulley to prevent the steel belt from meandering and to ensure that the driving force of the drive pulley is transmitted to the endless belt.

FIG. 6 shows an embodiment of a fixing device in which sprockets are provided at both ends of the drive pulley and feed holes are provided in the steel belt 1 to engage with the sprockets.

FIG. 7 shows another embodiment for preventing meandering of a metal endless belt. Drive pulley 2
rotates at an angle θ with respect to the axis of the backup roller 4, and the backup roller 4 of the drive pulley 2 rotates at an angle θ with respect to the axis of the backup roller 4.
A flange 2f that is freely tiltable and rotatable with respect to the axis of the drive pulley 2 is provided at the end closer to the drive pulley 2. When the belt 1 is driven by the pulley 2 whose axis is tilted, the belt always moves in the direction where the tension is smaller, that is, in the direction where the belt loosens. Therefore, when the drive pulley 2 is tilted with respect to the backup roller axis as in this embodiment, the steel belt 1 moves to the end closer to the backup roller 4 and is driven along the flange 2f. Further, the connection between the drive pulley 2 and the flange 2f is as shown in FIG. 8 so that the end of the steel belt 1 is not damaged by the flange 2f.
The flange 2f is configured to freely incline and rotate with respect to the drive pulley 2.

[0025]

[Effects of the Invention] According to the present invention, the endless belt can run stably without using alignment control of the driving pulley of the endless belt, and furthermore, since the endless belt is made of metal material such as steel, it has sufficient strength. This has the effect of reducing costs and improving the life of the endless belt.

Furthermore, since the surface roughness can be freely set, it is easier to coat the surface with fluororesin such as PFA or PTFE than with polyimide resin belts used as conventional endless belts, and the adhesive strength of these belts can be improved. There is also the effect that you can get enough.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view of an electrophotographic apparatus including an embodiment of the present invention.

FIG. 2 is a perspective view showing one embodiment of the present invention.

FIG. 3 is a configuration diagram of a temperature control device used in this example.

FIG. 4 is a sectional view of the metallic endless belt used in this example.

FIG. 5 is a shape diagram showing various drive pulleys of the present invention.

FIG. 6 is a perspective view showing another embodiment of the present invention.

FIG. 7 is a perspective view showing still another embodiment of the present invention.

FIG. 8 is a diagram showing a connection between a drive pulley and a flange in the embodiment of FIG. 7;

[Explanation of symbols]

1 steel belt 1a
Fluorine resin layer 2 Drive pulley
2a~2d Drive pulley

Claims (9)

[Claims] 1. A heating resistor, an endless belt disposed to cover the heating resistor, a drive pulley that drives the endless belt, and a backup roller that presses paper against the heating resistor via the endless belt. 1. A heat fixing device comprising: a metallic endless belt having a fluororesin layer on a surface that contacts the paper; 2. The heat fixing device according to claim 1, comprising:
A heat fixing device characterized in that the width of the Endos belt is larger than the width of the backup roller. 3. The heat fixing device according to claim 1, comprising:
The heat fixing device according to claim 1, wherein the drive pulley has a guide that guides both ends of the endless belt. 4. The heat fixing device according to claim 1, comprising:
The drive pulley has a shape such as a linearly tapered shape in which the pulley diameter becomes smaller in the axial direction, and has a guide at the end of the pulley with the smaller diameter for guiding the side end of the endless belt. Heat fixing device. 5. The heat fixing device according to claim 1, comprising:
The drive pulley is inclined so that the extension of its axis intersects the extension of the axis of the backup roller at a certain point, and the drive pulley has a side end of the endless belt at the end of the drive pulley that is closer to the backup roller. 1. A heat fixing device characterized in that a guide is provided for guiding the drive pulley, and the guide is tiltable and rotatable with respect to the axis of the drive pulley. 6. The heat fixing device according to claim 1, comprising:
A heat fixing device characterized in that the drive pulley has sprockets at both ends thereof, and feed holes that engage with the sprockets are provided at both ends of the endless belt. 7. The heat fixing device according to claim 1,
A heat fixing device characterized in that the drive pulley has means having a large friction coefficient at a contact portion between the drive pulley and the endless belt. 8. The heat fixing device according to claim 1,
The heat fixing device is characterized in that the backup roller has an inverted crown shape with a diameter decreasing at the center. 9. An electrophotographic apparatus comprising the heat fixing device according to claim 1.