JPH0365976A - Fixing device - Google Patents

Abstract

PURPOSE:To stably and accurately bring an endless belt into pressurized contact with a fixing roller by forming the endless belt unit in such a manner that the unit can oscillate around the pivotal fulcrum provided on the supporting parts at both roller shaft ends of the endless belt unit and can move in the directions attaching to or detaching from the fixing roller, then bringing such belt unit to pressurized contact with the fixing roller. CONSTITUTION:Roller supporting plates 10 by which the rollers 4, 5 are supported are fitted to pivotally supporting shafts 14 and the endless belt unit 11 itself is constituted freely oscillatable around the pivotally supporting shafts 14 in the state of supporting the same at both ends. A compression spring 18 is interposed between a body side plate 12 and a spring rest 17 engaged thereon and a pressurizing lever 16 pushes up the endless belt unit 11 itself via the pivotally supporting shaft 14. Such function is easily attained in such a manner even if the accuracy of the supporting parts of the endless belt unit is not enhanced. The passing time of a sheet 7 to be fixed is thereby uniformized and the pressurizing contact force is uniformized and, therefore, the fixing is stably executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fixing device that heats and fixes a developed toner image on a sheet to be fixed.

[Conventional technology]

2. Description of the Related Art Some image forming apparatuses, such as copying machines, printers, and facsimile machines, are equipped with a fixing device that fixes a toner image formed on the surface of transfer paper, recording paper, or the like.

Among such fixing devices, a sheet to be fixed, such as transfer paper or recording paper, is sandwiched and conveyed between a fixing roller that has an internal heat source and an endless belt, and the toner image on the sheet is heated and fixed. This type of fixing device has been known for some time (see Utility Model Application Publication No. 59-173071, etc.).

In this type of fixing device, the part of the belt that comes into contact with the fixing roller needs to be pressed against the fixing roller stably, with the same pressure, and at a contact angle that does not fluctuate. If the configuration is not taken into consideration, fixing performance will be greatly affected.

Therefore, in order to create a fixing device that takes these points into consideration, an auxiliary roller is placed between a pair of rollers on which an endless belt is stretched.
A fixing device as shown in Japanese Patent Laid-Open No. 60-151677, etc., is conventionally known, in which a belt portion between the auxiliary roller and one of a pair of rollers is brought into pressure contact with a fixing roller. It has become a place where people can be exposed.

Further, in JP-A-61-1898, each of a pair of rollers on which an endless belt is stretched is movably supported separately, and each is biased toward the fixing roller by the elasticity of a spring.
2. Description of the Related Art Fixing devices such as those disclosed in Japanese Patent No. 2 and the like have been known for some time.

[Problem to be solved by the invention]

Such a fixing device requires an auxiliary roller or has a configuration in which each of the pair of rollers is independently supported, which tends to make the device configuration complicated.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device that has a simple configuration and can stably and accurately press an endless belt against a fixing roller.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention includes a fixing roller having an internal heat source and a fixing roller stretched between a pair of rollers, in which a sheet to be fixed is sandwiched. and an endless belt for conveyance, and the endless belt is constituted as an endless belt unit in which the roller shaft ends of the pair of rollers are rotatably supported by one roller support plate on each side. , and each roller support plate is movable toward and away from the fixing roller by being swingable around a pivot point provided between one roller shaft end support portion and the other roller shaft end support portion. The present invention proposes a configuration in which a biasing means is provided for moving and biasing the endless belt unit in a direction in which the endless belt comes into pressure contact with the fixing roller.

〔Example〕

Embodiments of the present invention will be described below with reference to one drawing.

In FIG. 1, reference numeral 1 indicates a fixing roller that is rotated in the direction of the arrow in the figure, and a heater 2 that is a heat source is installed inside the fixing roller.
is provided, and the heater 2 is controlled on and off so that the surface of the fixing roller 1 is maintained at a set temperature.

The endless belt 3 is stretched between a pair of rollers 4 and 5, and when it is at the position indicated by the broken line, it is in pressure contact with the fixing roller 1, and in this state, it follows the rotation of the fixing roller 1 and moves in the direction of the arrow shown in the figure. It is designed to rotate.

On the other hand, a sheet 7 to be fixed, such as transfer paper or recording paper (print paper), is sent from the guide plate 6 toward the space between the fixing roller 1 and the endless belt 3. The sheet to be fixed 7 which has entered between the two members 1 and 3 is conveyed while being held between the two members, and the toner image 8 on the sheet to be fixed 7 is fixed by heat and pressure during this time.

In FIG. 2, each roller shaft end 4 of a pair of rollers 4 and 5 is shown.
The a and 5a sides are rotatably supported by roller support plates 10 and 10, one on each side, so as to maintain a predetermined distance between the rollers (this will be described later).

By supporting each of the rollers 4 and 5 by the roller support plate 10, the endless belt consists of the endless belt 3, the rollers 4 and 5, and the member supporting them (the roller support plate 10). ) etc. are integrated into an endless belt unit.

Each main body side plate 12 of an image forming apparatus such as a copying machine, a facsimile machine, and a printer is provided with a vertically elongated guide hole 13 opened at the upper end thereof, and a pivot shaft 14 is provided in this guide hole 13 so as to be vertically movable. It's embedded. This pivot shaft 14 holds the side plates 12 of the main body so that it can stably move up and down while maintaining a position parallel to the axial direction of the rollers 4 and 5 (see Fig. 4). is attached on its axis. In addition, in FIG. 2, illustration of this is omitted for convenience.

In FIG. 2, the roller support plate 10 is fitted onto such a pivot shaft 14, and the endless belt unit 11 itself is swingable around the pivot shaft 14 in a state where it is supported on both sides. That is, the endless belt unit 11 has a pivot point (pivot shaft 1
4) can be swung around.

In addition, the endless belt unit 11, as shown in FIG.
Since the pivot shaft 14 is movable in the vertical direction while being guided by the guide hole 13, it is also movable in the vertical direction. That is, it is movable in the direction toward and away from the fixing roller 1.

The base end of a pressure lever 16 (the inner part is not shown) is pivotally attached to both main body side plates 12. 18 is interposed, and the elasticity of this spring 18 gives the pressure lever 16 the habit of rotating in the direction of pushing up the pivot shaft 14.

With the spring 18 assembled, the pivot shaft 14 is pushed up by the elasticity of the spring, and the endless belt 3 is accordingly placed in the pressure position shown by the broken line in FIG. The spring 8 constitutes a configuration example of a biasing means for biasing the endless belt unit 11 itself to move in a direction in which the endless belt 3 comes into pressure contact with the fixing roller 1 .

By assembling the spring 18, the pressure lever 16 is rotated in the above direction due to the elasticity of the spring, and the pivot shaft 14 is rotated.
As the endless belt unit 11 itself is pushed up via the arrow , the endless belt 3 at the position shown by the solid line, which was away from the fixing roller 1 as shown in FIG. 1, has a contact angle with the fixing roller 1 as shown by the broken line. Pressure contact is made with θ.

Now, if the endless belt unit itself is configured such that it cannot swing around the pivot shaft 14, the contact angle θ and the contact position may change. In addition, uneven contact may occur, resulting in uneven pressure contact.

In order to avoid such a situation, it is possible to improve the support accuracy of the endless belt unit itself with respect to the main body side plate 12, but in this case, increasing the accuracy to a certain extent will not be enough to keep up, and the equipment cost will increase. will rise significantly.

However, in this example, the endless belt unit itself is configured to be able to freely swing around the pivot shaft 14, so when the endless belt 3 is in pressure contact with the fixing roller 1,
The uneven contact as described above is less likely to occur, and the pressing force becomes uniform in the circumferential direction of the fixing roller 1. In addition, the contact angle θ is less likely to fluctuate, and misalignment of the pressure contact position is also less likely to occur. As a result, the conveyance of the sheet 7 to be fixed is ensured, and the passage time thereof is made constant, and the pressure contact force is also made uniform, so that fixing performance is improved and fixing is performed stably. Such a function can be easily achieved without increasing the precision of the support portion of the endless belt unit.

Note that when the distance between the rollers 4 and 5 changes, the tension of the endless belt 3 changes, but the distance between the rollers 4 and 5 is adjusted so that the belt tension is such that a contact angle of θ is obtained when the endless belt 3 is in pressure contact. It is set in advance.

In this example, there is no need for the auxiliary rollers mentioned above, and since the rollers 4 and 5 are not energized separately, the number of parts is reduced, and the fixing device configuration can be greatly simplified. It can be simplified to Further, in the case of using separate urging means, if there is a difference in the respective urging forces, the belt pressing force may become uneven, but this example eliminates such a fear.

〔Effect of the invention〕

According to the configuration of the present invention, fixing performance is improved and fixing is performed stably, so that high-quality fixed images can be stably obtained, and this can be achieved with an extremely simple configuration. can.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a fixing device according to an embodiment of the present invention, and FIG.
The figure is a perspective view of the structure of the endless belt unit included in the fixing device of the embodiment, FIG. 3 is a diagram showing the movable support component of the endless belt unit, and FIG. 4 is a diagram showing the main parts of the movable support component. FIG. 1... Fixing roller 2... Heater 3... Endless belt 4, 5... Pair of rollers 4a, 5a...
・Roller shaft end゛°°Fixed sheet 10...Roller support plate Oa・
...One roller shaft end support part ob...Other roller shaft end support part work...Endless belt unit 4...Pivot shaft (pivot point)

Claims (1)

[Claims] A fixing roller having an internal heat source, and an endless belt stretched between a pair of rollers to sandwich and convey a sheet to be fixed between the fixing roller, the endless belt comprising:
The roller shaft end side of the pair of rollers is configured as an endless belt unit in which the roller shaft end sides of the pair of rollers are rotatably supported by one roller support plate on each side, and one roller shaft end support portion of each roller support plate and the other roller shaft end support portion of each roller support plate The endless belt is configured to be able to swing around a pivot point provided between the roller shaft end support portion and to be movable in the direction toward and away from the fixing roller, and in the direction in which the endless belt comes into pressure contact with the fixing roller. The fixing device further comprises a biasing means for movably biasing the endless belt unit.