JPH05338894A - Fixing device - Google Patents

Abstract

PURPOSE:To enable discharge of recording paper which is as straight as new ones by avoiding, whatever service conditions, curving of recording paper which occurs when the recording paper on which a developed image is fixed by a fixing device is discharged. CONSTITUTION:Heating means 22 for fusing an image developed on recording paper 21 by a developing agent to the recording paper are provided and guide members 25, 26 for guiding the direction in which the recording paper 21 travels are provided in such a manner that they can be adjusted so that after passing through the heating means 22 the recording paper 21 has its direction of travel changed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device in an image forming apparatus such as a copying machine, a laser beam printer and a facsimile.

[0002]

2. Description of the Related Art In recent years, an image forming apparatus, particularly an image forming apparatus using an electrophotographic system, can use plain paper in a copying machine, a laser beam printer, a facsimile, and the like.
As office equipment for high-quality and high-speed hard copy,
It is used in a wide range, and in this type of image forming apparatus, a fixing device that fixes a visible image on recording paper by heating and melting a developer is generally used.

A fixing device of this type is disclosed in JP-A-3-16758.
It is known from Japanese Patent Publication No. 2 and the like. Referring to the drawings below,
An example of the above-mentioned conventional image forming apparatus will be described.

FIG. 6 is a conceptual view of a cross section of a conventional fixing device. In the figure, 1 is a recording sheet, 2 is a heat roller for applying heat to a developer, 3 is a pressure roller for pressing the recording sheet 1 against the heat roller 2, 4 is a separating claw, and the recording sheet 1 is from the heat roller 2. When a separation failure occurs, they are forcibly separated, and 5a and 5b are guide members for the recording paper 1, and 6a and 6b are discharge roller pairs for discharging the recording paper 1 to the outside of the fixing device.

The operation of the fixing device configured as described above will be described below with reference to FIGS. 6 and 7.

First, the recording sheet 1 on which a visible image is formed by a developer using an apparatus (not shown) provided in the image forming apparatus enters the pressure contact portion between the heat roller 2 and the pressure roller 3, and the recording sheet 1 Is pressed against the heat roller 2 by the pressure roller 3. As a result, the developer on the recording sheet 1 is heated by the heat roller 2 and is fused to the recording sheet 1. After that, the recording sheet 1 is discharged onto the discharge roller pair 6a,
It enters the pressure contact portion 6b and is discharged to the outside of the fixing device.

In this process, since the recording paper 1 is heated by the heat roller 2, the recording paper 1 as a whole is in a state of being easily plastically deformed.

In this state, the recording paper 1 is pressed against the heat roller 2 by the pressure roller 3,
As shown in FIG. 5, the recording paper 1 is deformed into a surface shape having a curvature, and a force for bending the recording paper 1 is generated.

The surface of the recording paper 1 that contacts the heat roller 2 that is directly heated becomes higher in temperature than the surface that contacts the pressure roller 3, so that the heat roller 2 is heated.
The amount of heat applied to the surface in contact with is larger than the amount of heat applied to the surface in contact with the pressure roller 3, and the amount of evaporation of water due to application of heat increases. The recording paper 1 shrinks when water evaporates, but due to the above reasons, the side of the surface in contact with the heat roller 2 has a larger shrinkage rate due to the evaporation of water than the side of the surface in contact with the pressure roller 3. This also causes the recording paper 1 to be bent.

The recording paper 1 in a state where plastic deformation is likely to occur when heat is applied is easily bent by these bending forces. This curvature is
After the recording paper 1 has passed through the pressure contact portion between the heat roller 2 and the pressure roller 3, the recording paper 1 advances in the direction opposite to the curving direction when there is residual heat, that is, when it is still rigid and plastically deformable. The direction is corrected by the guide member 5a, enters the pressure contact portion of the discharge roller pair 6a, 6b, and is discharged to the outside of the fixing device without causing severe bending.

[0011]

However, in the above-mentioned structure, the recording paper 1 has a residual heat due to the positional relationship between the pressure contact portions of the heat roller 2 and the pressure roller 3 and the pressure contact portions of the discharge roller pairs 6a and 6b. In a certain state, the direction of the path of the recording paper 1 after the recording paper 1 has passed through the pressure contact portion of the heat roller 2 and the pressure roller 3 is corrected while proceeding in a direction opposite to the direction of the generated curvature. It is fixed in one direction.
Therefore, the recording sheet 1 discharged from the pair of discharging rollers 6a and 6b has the curvature sufficiently removed only under specific use conditions.

On the other hand, the amount of bending that occurs on the recording paper 1 varies in various ways depending on changes in usage conditions. For example, specifically, the amount of bending is large when used under high temperature and high humidity, and the amount of bending is small when used under low temperature and low humidity. This is because under high temperature and high humidity, the recording paper 1 has a large water content and a large amount of water vaporized, so that the influence of the difference in the evaporation amount on both sides of the recording paper 1 becomes large, and the difference in the contraction rate on both sides is large. On the other hand, under low temperature and low humidity, the recording paper 1 has a small water content and a small amount of water vaporized, so that the influence of the difference in the evaporation amount on both sides of the recording paper 1 is small, and the difference in the shrinkage rate on both sides is small. ..

As the use conditions change as described above, the amount of bending given to the recording sheet 1 varies,
Even in that case, in the fixing device having the above-described configuration, since the correction amount of the curvature is constant, it becomes impossible to deal with the variation of the curvature amount. That is, there is a problem that it is impossible to sufficiently remove the generated curvature under a condition other than a specific use condition.

In view of the above problems, the present invention provides a fixing device capable of discharging recording paper without curving under any use condition.

[0015]

In order to solve the above-mentioned problems, a fixing device of the present invention comprises a heating means for heating a visible image by a developer formed on a recording sheet and a recording sheet heated by the heating means. And a guide member that can be adjusted to change the traveling direction.

Further, the control member for adjusting the guide member according to the amount of curvature after the recording paper is heated by the heating means so that the curvature generated in the recording paper is always removed under any use condition. It is equipped with.

[0017]

According to the present invention, the guide member for the recording sheet has the above-described structure even if the amount of bending of the recording sheet after passing through the heating means is changed due to changes in usage conditions such as the water content of the recording sheet and the usage environment. By adjusting, the recording paper advances in the direction to remove the curvature properly when there is residual heat that can be plastically deformed, so the curvature of the recording paper is corrected and is approximately the same as the unused recording paper. It is possible to discharge the recording paper, on which the visible image of the developer is fixed, which is not curved, from the fixing device.

Further, by providing a control member for adjusting the guide member according to the amount of bending of the recording paper after being heated by the heating means, the amount of bending of the recording paper is properly removed, so that any use is possible. Even under the conditions, it is possible to always correct the curvature properly.

[0019]

EXAMPLE A fixing device according to an example of the present invention will be described below.
A description will be given with reference to the drawings.

FIG. 1 is a conceptual view of a cross section of a fixing device according to the first embodiment of the present invention. 21 is a recording sheet, 22 is a heat roller for applying heat to the developer, 23 is a pressure roller for pressing the recording sheet 21 against the heat roller 22, 24 is a separating claw, and the recording sheet 21 is the heat roller 22.
Is forcibly separated when a separation failure occurs, and 25 and 26 are guide members of the recording paper 21 whose directions can be adjusted in conjunction with each other, and 27a and 27b are the recording paper 21.
A discharge roller pair for discharging the sheet to the outside of the fixing device, 28 is a fulcrum for the rotation of the guide members 25, 26 and the discharge roller pair 27a, 27b, and 29 is a sensor.
Detects the amount of bending after passing through the pressure contact portion between the heat roller 22 and the pressure roller 23, and 30 is an adjusting mechanism for adjusting the directions of the guide members 25, 26 and the discharge roller pairs 27a, 27b.

The operation of one embodiment of the fixing device of the present invention constructed as described above will be described with reference to FIGS.

First, as in the case of the conventional example, the recording paper 21 on which a visible image is formed by the developer by using a device (not shown) provided in the image forming apparatus is a press contact portion between the heat roller 22 and the pressure roller 23. Then, the recording paper 21 is pressed against the heat roller 22 by the pressure roller 23. As a result, the developer on the recording paper 21 is heated by the heat roller 22 and is fused to the recording paper 21.
After that, the recording paper 21 enters the pressure contact portion of the discharge roller pair 27a, 27b and is discharged to the outside of the fixing device.

The recording paper 21 in a state in which it is apt to undergo plastic deformation by being given heat is easily bent by the above-mentioned bending force. The curving is caused by the guide member 25 in a state where there is residual heat after the recording paper 21 passes through the pressure contact portion between the heat roller 22 and the pressure roller 23, that is, when the recording paper 21 is still rigid and plastically deformable. Is corrected by advancing the recording paper 21 in the direction opposite to the direction of the discharge roller pair 27a,
It enters into the pressure contact portion of 27b and is discharged out of the fixing device without causing severe bending. However, if the passage of the recording paper 21 is in one specific direction, the amount of correction of the curvature is constant even if the amount of curvature changes due to changes in usage conditions, and the recording paper discharged from the fixing device at this time. 21
Is not always well-curved.

For example, as described in the conventional example, the recording paper 2
When the water content of 1 is large, the amount of bending generated on the recording paper 21 is large, and when the water content of the recording paper 21 is small, the amount of bending generated on the recording paper 21 is small. According to the present invention, when the recording sheet 21 has a large curvature and the recording sheet 21 travels to the guide member 25 side in FIG.
As shown in FIG. 3, according to the output of the sensor 29, the adjusting mechanism 30 is operated so that the guide member 25 rotates in the direction of arrow C in FIG. 1, and there is residual heat and plastic deformation is possible. When the recording sheet 21 is in the state, the curving is removed by largely correcting the traveling direction in the direction opposite to the curving direction. In this way, since the recording paper 21 enters the pressure contact portion of the discharge roller pair 27a, 27b with the curvature removed, the recording paper 21 is discharged from the fixing device in an appropriate state without curvature.

On the other hand, when the curvature of the recording paper 21 is small and the recording paper 21 does not move so much toward the guide member 25 side in FIG. 1, the correction amount toward the guide member 26 side in the direction of the guide member 25 shown in FIG. Is too large, the recording paper 21 is given a curve toward the guide member 26 side. According to the present invention, under such conditions,
As shown in FIG. 4, by operating the adjusting mechanism 30 according to the output of the sensor 29 so that the guide member 25 rotates in the direction of arrow D in FIG. 1, there is residual heat and plastic deformation is possible. In such a state, the recording paper 21 is corrected by an appropriate amount in the opposite direction to the curving direction without correcting the advancing direction excessively. Therefore, the recording paper 21 is not curved to the guide member 26 side. In this way, the recording paper 21 enters the pressure contact portion of the discharge roller pair 27a, 27b in a state where the curving due to unnecessary correction is not applied, and therefore the recording paper 21 is ejected from the fixing device in an appropriate state without curving. It

As described above, according to this embodiment, the guide members 25 and 26 and the discharge roller pairs 27a and 27b that determine the advancing direction of the recording paper 21 are rotated so as to change the advancing direction of the recording paper 21. By being movably provided, even if the recording paper 21 is deformed by any size at a high temperature to cause plastic deformation, it is properly corrected by correcting an appropriate amount when there is residual heat. The curvature can be removed, and the recording paper 21 without curvature can be ejected from the fixing device.

FIG. 5 is a conceptual sectional view of a fixing device showing a second embodiment of the present invention. 1 is different from the configuration of FIG. 1 in that it is provided as a means for applying heat to the recording paper 41 so as to be in pressure contact with the endless film 43 running on the heating body 42. The recording paper 41 on which a visible image is formed by the developer runs on the endless film 43 and the pressure roller 4.
4, the recording paper 41 is pressed by the pressing roller 44 and comes into close contact with the running endless film.
At this time, the developer that forms a visible image on the recording paper 41 is heated by the heating body 42 through the endless film 43 that travels and is fused on the recording paper 41.

Also in this embodiment, similarly to the first embodiment, the guide member 4 for determining the traveling direction of the recording paper 41 is used.
5, 46 and the discharge roller pairs 47a, 47b are rotatably provided so that the advancing direction of the recording sheet 41 can be changed, so that the recording sheet 41 is deformed by any size when the recording sheet 41 is at a high temperature and is plastic. Even if a deformation occurs, it can be properly corrected, and the recording paper 41 having no curvature is formed.
Can be discharged from the fixing device.

Incidentally, the sensor 29 in the above-mentioned two embodiments.
Is a switch that operates in multiple stages by rotating in the direction shown by arrow E in FIG. 1, and if an actuator that performs linear motion is used as the adjusting mechanism 30, for example, it can be adjusted according to the amount of bending of the recording paper 21. It is possible to make a configuration in which the actuator is activated in accordance with the switching.

Further, since the amount of bending of the recording paper 21 mainly depends largely on the environment, particularly the humidity, the sensor 29 serves as a humidity sensor at a position other than the position shown in FIG. It is also possible to operate the adjusting mechanism 30 based on the relationship between the humidity and the amount of water contained in the recording paper 21 and the amount of bending, which are provided in the storage area of the recording sheet 21 and operated.

[0031]

As described above, the fixing device of the present invention advances to the heating means for heating the recording paper with the visible image formed by the developer formed on the recording paper, and the heating of the recording paper by the heating means. With a guide member that guides the direction,
By making the guide member adjustable so as to change the traveling direction of the recording sheet, the curved recording sheet can be plastically deformed and is corrected when there is residual heat. Therefore, it is possible to eject the recording sheet having no curve regardless of the use conditions.

Furthermore, by providing a control member that adjusts the guide member according to the amount of bending of the recording paper after being heated by the heating means, a recording paper that does not always have proper curvature under any use condition is provided. Can be discharged.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a cross section of a fixing device according to a first exemplary embodiment of the present invention.

FIG. 2 is a cross-sectional view of the fixing device of the embodiment showing the details of the pressure contact portion between the heat roller and the pressure roller.

FIG. 3 is an operation explanatory view of the fixing device of the present invention.

FIG. 4 is an operation explanatory view of the fixing device of the present invention.

FIG. 5 is a conceptual diagram of a cross section of a fixing device according to a second embodiment of the present invention.

FIG. 6 is a conceptual diagram of a cross section of a conventional fixing device.

FIG. 7 is a cross-sectional view of a conventional fixing device showing details of a pressure contact portion between a heat roller and a pressure roller.

[Explanation of symbols]

 1 Recording Paper 2 Heat Roller 3 Pressure Roller 4 Separation Claw 5a, 5b Guide Member 6a, 6b Discharge Roller Pair 21 Recording Paper 22 Heat Roller 23 Pressure Roller 24 Separation Claw 25 Guide Member 26 Guide Member 27a, 27b Discharge Roller Pair 28 Support 29 Sensor 30 Adjustment mechanism 41 Recording paper 42 Heater 43 Endless film 44 Pressure roller 45 Guide member 46 Guide member 47a, 47b Discharge roller pair 48 Support point 49 Sensor 50 Adjustment mechanism

Claims (2)

[Claims] 1. A heating unit for heating a visible image formed by a developer formed on a recording sheet, and a guide member which can be adjusted so as to change a traveling direction after the recording sheet is heated by the heating unit. And a fixing device. 2. The fixing device according to claim 1, further comprising a control member that adjusts the guide member in accordance with a curving amount after the recording paper is heated by the heating means.