JPS60151678A - Fixing device - Google Patents

Abstract

PURPOSE:To prevent an endless belt from meandering by providing a collar that has a larger diameter than the center part of a support roll which is longer than the width of the supported endless belt to the end part of the support roll and a groove inside of it, and bending and fitting the end of the endless belt in the groove. CONSTITUTION:The endless belt 18 is extended between support rolls 16 and 17 and wound around a heat roll 15 by prescribed length. The axial length of the support rolls 16 and 17 is larger than the width of the endless belt 18, diameters of its end parts 16a and 17a are made a little bit larger than the diameter of a heat insulating layer 23, and grooves 16c and 17c are formed inside of them. The end part of the endless belt 18 is bent to form an interlocking part 18a, which is fitted in the grooves 16c and 17c. Consequently, the endless belt 18 is prevented from meandering to fix an image stably on copy paper.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a fixing device that fixes a toner image onto a copy paper by conveying the copy paper on which a toner image is formed while being brought into pressure contact with a heating roll. It is something.

Conventional Structures and Problems Recently, there has been a demand for copying machines to be smaller and lighter, and with this, similar demands have been made for the fixing device, which is one of the devices in the copying machine. Conventionally, as a fixing device of a copying machine, an oven type fixing device or the like using a radiant type 1 heating element that fixes with infrared rays has been used. However, since the fixing method described above increases the size of the device, a heat roll type fixing device is most commonly used these days.

FIG. 1 shows a sectional view of this heat roll type fixing device. In FIG. 1, reference numeral 1 designates a heating roll 2 a pressure roll. The heating roll 1 has a hollow roll 3 made of a metal with good thermal conductivity such as aluminum, and a coating 4 made of heat-resistant and releasable polytetrafluoroethylene resin or the like is formed on the surface of the hollow roll 3. A heater 5 such as a rogen lamp is arranged and configured.

On the other hand, the pressure roll 2 is constructed by covering a core metal roll 6 with a heat-resistant thick elastic layer 7 made of silicone rubber or the like. Due to this elastic deformation of the elastic layer 7, the pressure contact portion between the heating roll 1 and the pressure roll 2 has a width of 11 mm in the rotational direction of the rolls.
B (hereinafter referred to as nip width). In the fixing method using the heat roll method, the inner peripheral surface of the hollow roll 3 is heated by radiant heat from the heater 6 disposed inside the heat roll, and the coating layer 4 on the outer peripheral surface of the hollow roll 3 is heated by the radiant heat from the heater 6 disposed inside the heating roll. A pressure roll 2 is heated by heat conduction and is placed in pressure contact with the heating roll 1.
By passing the copy paper P on which the toner image T has been formed between them, the toner image formed on the copy paper is fixed. In the above-mentioned fixing method, when an attempt is made to reduce the size and weight of the fixing device by reducing the roll diameter, problems such as poor fixing or paper wrinkles occur. This is because, in the fixing method, the fixability of toner to copy paper depends on the nip width, the pressure contact force between the heating roll and the pressure roll, and the time it takes for the copy paper to pass between the heating roll and the pressure roll. This is because it is determined by the surface temperature of the heating roll. In other words, to improve fixing performance, increase the nip width, increase the contact force between the heating roll and pressure roll, and increase the time that copy paper passes between the heating roll and pressure roll. In other words, the surface temperature of the heating roll is increased.

For the reasons mentioned above, if you simply reduce the roll diameter for downsizing, the width of the roll will also become smaller, which will make it harder to fix.
Since the stress due to the deformation of the elastic body in the second and width portion of the press roller relative to the diameter of the pressure roll becomes considerably large, the stress due to the deformation of the elastic body is applied to the copy paper between the rolls, causing paper wrinkles. In addition, if the roll diameter is made smaller, the diameter of the core roll will also be smaller, and if the pressing force between the heating roll and the pressure roll becomes too large, the pressure roll will bend due to poor mechanical strength of the core material, resulting in fixation. This may cause defects or paper wrinkles. Furthermore, if the time required for the copy paper to pass between the heating roll and the pressure roll is increased, the speed of the copying machine cannot be increased. Further, the surface temperature of the heating roll depends on the toner used and cannot be made higher than necessary.

A fixing device as shown in FIG. 2 has been proposed to eliminate the problems of the roll-pair type fixing device using heat rolls as described above. The fixing device shown in FIG. 2 includes an endless belt 10 rotatably mounted and supported by two support rolls 8 and 9, and
The copy paper P on which the toner image T is formed passes between the heating roll 11 and the endless belt 10, and the nip at the pressure contact area between the heating roll 11 and the endless belt 10 is provided. Copy paper P by width lB
The upper toner image T is fixed. The heating roll 11 of the fixing device is a hollow roll 12 of a metal with good thermal conductivity such as aluminum, and a coating 13 of polytetrafluoroethylene resin or the like having heat resistance and mold releasability is formed on the surface of the hollow roll 12. A roll can be used in which a heater 14 such as a halogen lamp is disposed inside the roll 12.

By adopting the above configuration, the nip width of the pressure contact portion between the endless belt and the heating roll can be made larger than the nip width of a fixing device using a conventional pair of rolls, thereby improving fixing performance. Moreover, the roll diameter can be reduced due to the improved fixing performance, and the device can be made smaller than a conventional fixing device using a pair of rolls.

However, in a fixing device using an endless belt as shown in Fig. 2, when the endless belt runs.

A deviation of the endless belt, that is, a meandering occurs in a direction perpendicular to its feeding direction, that is, in the direction of the axis of the endless belt support roll. Unfortunately, the belt protrudes beyond the end of the support roll, damaging the edge of the endless belt.
This may cause paper wrinkles or poor fixing. Here, if the roll supporting the endless belt and the heating roll were perfectly cylindrical and in a parallel positional relationship, and the dimensional accuracy of the endless belt was high, the above problem would not occur. However, in reality, it is difficult to achieve such machining accuracy, and meandering occurs. In order to suppress such meandering of the endless belt, for example, a sensing member is provided for displacement in the axial direction of the endless belt support roll, and when the belt meanders, the sensing member senses and tilts the support roll of the endless belt. It is conceivable to control the displacement of the endless belt in the axial direction of the support roll by returning the endless belt to its original position. It is also conceivable to attach a crown to the support roll of the endless belt. However, all of these systems have complicated mechanisms and may even cause fixing failure.

OBJECTS OF THE INVENTION The present invention eliminates the above-mentioned problems of the prior art.
It is an object of the present invention to provide a fixing device that can suppress meandering of a belt and fix a toner image formed on copy paper into a stable image.

Structure of the Invention The fixing device of the present invention includes an endless belt rotatably supported by a plurality of support rolls, and a heating roll that is in pressure contact with the endless belt, and the support roll is configured to support the endless belt. The endless belt has a roll length longer than the width and an end portion having a diameter larger than the diameter of the supporting portion of the endless belt, and a groove is provided at the boundary between the end portion and the supporting portion of the belt, The meshing portion is configured to fit into the groove provided on the support roll along the peripheral edge of the endless belt, so that the meshing portion provided on the endless belt is connected to the end of the support roll of the endless belt. The endless belt fits into the groove provided in the support roll and suppresses the meandering force in the axial direction of the support roll, thereby suppressing the meandering of the endless belt.

Description of examples Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 3 is a cross-sectional view of a fixing device according to an embodiment of the present invention, viewed at right angles to the roll axis, to FIG. 4 is a cross-sectional view of the endless belt, and FIG. 5 is a cross-sectional view of the support roll viewed parallel to the roll axis. figure,
FIG. 6 is a cross-sectional view showing the state of the endless belt and support roll when viewed parallel to the roll axis. First, in FIG. 3, 15 is a heating roll, 1θ, 17 is a belt support roll, and 18 is an endless bell. The heating roll 15 consists of an aluminum hollow roll 19 whose surface is coated with polytetrafluoroethylene resin 20 which has heat resistance and mold releasability, and a halogen lamp heater 21 is arranged inside the hollow roll 19. ing. support roll 16,
As shown in FIG. 3 and FIG. The diameter is the diameter of the support portions 16b, 17b plus twice the thickness of the endless belt 18, and grooves are further provided at the boundaries between the ends 16a, 17b of the support rolls 16, 17 and the support portions 16b, 17b of the endless belt 18. 16C
117c is provided. The endless belt 18 is constructed by covering a cylinder woven from glass fiber with silicone rubber, and further having a mating portion 18a at its end as shown in FIG. 4. As shown in FIG. 6, an interlocking portion 18a provided on the endless belt 18 is configured to engage with grooves 16c and 17c provided on the support roll 16.17.

The operation of the fixing device of this embodiment configured as described above will be explained below. First, the heater 21 in the heating roll 15 brings the surface of the heating roll 15 to a temperature (usually about 150 to 200°C) that allows the toner to be thermally fixed onto the copy paper.
is heated to. The copy paper P on which the toner image T is formed passes between an endless belt 18 that is rotatably mounted and supported by support rolls 16 and 17 and a heating roll 15 that is in pressure contact with the endless belt 18. Then, the toner image T is fixed on the copy paper P. At this time, a meandering force F as shown in FIG. 6 is generated in the axial direction of the support roll 16°17. However, the interlocking portion 18 provided on the endless belt 18
a grooves 16c, 1 provided in the support roll 16.17
7c, the meandering force F acting in the axial direction of the support roll is suppressed, and the endless belt does not meander in the axial direction of the support roll.

Next, experimental data of this example will be shown. The heating roll 15 has an outer diameter of 30Ill+ll, a wall thickness of 1.5Ill1m+a length of 3
A support roll 16 was prepared by using a material coated with polytetrafluoroethylene resin to a thickness of 80 μm on the surface of a 00 ynm aluminum tube.
, 17 uses stainless steel for the core metal roll, and the core metal roll of the support part of the endless belt has a diameter of 1.
6111111, covered with 3 mm thick silicone rubber, and has a roll end diameter of 25 mm, and a width of 2.2 mm between the roll end and the supporting part of the endless belt.
mTL, 2.5m to the support part of the endless belt
For the endless belt 18, a cylinder woven from glass fiber is coated with silicone rubber to a thickness of 1.6 m, and a width of 2 m is used along the periphery of the end. Friend.

An experiment as described below was conducted using a belt having a 2MTK protrusion facing inside the circumferential edge of the belt. The surface temperature of the heating roll was maintained at 180°C, the feeding speed of the copy paper to the fixing device was set to 14°/sec, and the central part of the copy paper was K 30
Approximately 4,000 copies of A4 size copy paper with a solid black image of mm square were passed through the fixing device to observe the running condition of the endless belt. At this time, I Kp / a in the roll length width
The pressure of i was applied. As a result, no meandering or damage to the belt due to the endless belt falling off the support roll occurred even after about 4,000 sheets of copy paper were passed through. However, good fixing properties were also obtained.

As described above, according to this embodiment, a groove is provided at the end of the support roll of the endless belt, and a protrusion is provided along the periphery of the end of the endless belt toward the inside of the belt periphery. By fitting a protrusion that extends inward along the circumferential edge of the belt into the groove of the end of the endless belt, the meandering force acting in the axial direction of the support roll can be suppressed, making it possible to suppress the meandering of the endless belt. , even better fixing properties can be obtained. In addition, in the above-mentioned embodiment of the present invention, an aluminum tube was used as the hollow roll of the heating roll, but this is not limited to an aluminum tube, and the same effect can be obtained as long as the metal has sufficient mechanical strength. can get. Further, in the above embodiment, polytetrafluoroethylene resin was used for the coating layer on the surface of the heating roll, but the same effect can be obtained with silicone rubber.

Effects of the Invention As is clear from the above description, the present invention includes an endless belt rotatably supported by a plurality of support rolls, and a heating roll that is in pressure contact with the endless belt, and the support roll is The endless belt has a roll length greater than the width of the endless belt, an end portion having a diameter smaller than the diameter of the supporting portion of the belt, and a groove at the boundary between the end portion and the supporting portion of the endless belt, is configured to have an interlocking portion along the periphery of its end that fits into a groove provided on the support roll, so that the interlocking portion provided on the endless belt engages with the groove provided on the support roll of the belt. It fits into the groove provided at the end and suppresses the meandering force acting in the axial direction of the support roll, suppressing the meandering of the endless belt and fixing the toner image formed on the copy paper into a stable image. It has excellent features.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a conventional fixing device, FIG. 2 is a cross-sectional view of a fixing device considered as an improvement over the conventional example, FIG. 3 is a cross-sectional view of a fixing device according to an embodiment of the present invention, and FIG. 5 is a cross-sectional view of an example of the endless belt used in the present invention, FIG. 5 is a cross-sectional view of a support roll in an embodiment of the present invention, and FIG. 6 is a coupled state of the endless belt and support roll in an embodiment of the present invention. FIG. 15...Heating roll, 16.17...Supporting row knife 18--Endless belt, 19--Hollow roll, 20...Toner offset, gutter prevention layer,
21...Converter 122...Core metal roll, 23...Heat-resistant elastic layer, 16cl, 17'a...
...Support roll end, 16b. 17b... Belt support portion of support roll, 16c. 17c...Groove, 18a...Matching part,
T...Toner, P...Copy paper. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 2 δ Figure 3 Value 4 Figure 5 Male figure

Claims (3)

[Claims] (1) An endless belt rotatably supported by a plurality of support rolls, and a heating roll in pressure contact with the endless belt, and the support roll has a roll length larger than the width of the endless belt and the The endless belt has an end portion having a diameter larger than the diameter of the support portion of the endless belt, and a groove is provided at the boundary between the end portion and the support portion of the endless belt, and the endless belt has a groove along the periphery of the end portion. A fixing device comprising a mating portion that fits into a groove provided in a support roll. (2) Claim No. 1 (1) consisting of two support rolls
) The fixing device described in section 2. (3) The diameter of the end of the support roll is equal to the diameter of the portion supporting the endless belt plus twice the thickness of the endless belt. The fixing device described in section 1).