JPH02277089A - Fixing device for image forming device - Google Patents

Abstract

PURPOSE:To prevent paper wrinkle, etc., by providing such a means that allows a nip form to approximate to a set condition when the cross sectional shape of a pressure roll is deformed by a change in the heat distribution of the pressure roll. CONSTITUTION:Pressure f2 and f2 act on the pressure roll 10 from both sides of a shaft, however the force is practically applied to the central part of the pressure roll 10 to be strongly acted on the central part of a heat roll 5. On the other hand, since reaction forces F and F act on both sides of the shaft of the roll 5, the nip is formed between both rolls, shown by a symbol, Na, to establish a suitable condition for paper traveling. Thus, action by which the deformed nip form is automatically returned to its normal shape is added, so that the nip form suitable to the traveling of the paper in large size can be easily restored.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a heating roller type fixing device applied to an image forming apparatus that uses xerography type, such as an electronic copying machine or a printer, to create recording paper. In particular, the present invention relates to a device that can maintain a constant nip shape between both rollers.

(Prior Art) In devices configured to create recording paper using xerography, such as electronic copying machines and laser printers, a toner image formed on a photoreceptor drum is transferred to paper. Then, the paper is guided to the fixing device by the conveyance means. Then, in the fixing device, the toner is melted by applying heat or pressure, and the melted toner is pressed onto the paper to fix it, thereby completing the recording paper.

In order to perform fixing on the paper storage device as described above, a heating roller type fixing device is generally used in many cases. This heating roller type device consists of a heating roller with a built-in heating lamp and a pressure roller that is pressed against the heating roller with a predetermined pressure. Heat and pressure are applied to the paper nipped between the sheets to perform a fixing action.

As shown in FIG. 9, in the image forming apparatus, an optical system device is provided to irradiate the photosensitive drum 30 with light of an image of an original, and the light obtained by scanning the original is emitted. A means for irradiating the photoreceptor drum 30 is used.

Further, around the photosensitive drum 30, a charging corotron 31, a developing device 3
In addition to 2 and transfer/separation corotron 33, etc., a peeling claw,
Cleaning equipment etc. are installed.

Then, an electrostatic latent image is formed on the surface of the photoreceptor drum 30 by light from the image reading device, toner is supplied from the developing device to the electrostatic latent image, and the image is visualized as a toner image.
The toner image is transferred to the paper by electric discharge from the transfer corotron.

Further, the paper onto which the toner image has been transferred is conveyed by a conveyor belt device 35, passes through a guide plate 36, and passes through a fixing device 1.
The toner is introduced into the constant V device 1, nipped between the heating roller 5 and the pressure roller 10, and heat and pressure are applied thereto to perform fixing.

The fixing device has a heating roller 5 and a pressure roller 10 facing each other as shown in FIG. The heating roller 5
is connected to a drive device and is driven at a predetermined speed in accordance with the paper conveyance speed in the image forming apparatus.

As shown in FIG. 10, the fixing device includes a heating roller 5 which is supported by a bearing 3 on a frame 2 and whose end is connected to a drive mechanism, and which is arranged parallel to the heating roller 5. A heating source such as a halogen lamp 6 is provided inside the heating row 55.

The pressure roller 10 has a rubber layer 11 of a predetermined thickness around a vibrator 12 made of a metal cylindrical member.
A pressing means is provided for the bearing 13.13a that supports the shaft of the pressure roller 10, and a spring 14.14a serving as the pressing means presses it toward the heating roller 5. A constant nip pressure between the rollers is created.

By the way, in the heating roller type fixing device configured as described above, the shape of the nip portion of the paper between the heating roller and the pressure roller may be as shown in FIG. considered desirable.

In other words, the speed v2 on both sides is set approximately 0.2 to 0.3% faster than the conveyance speed v1 in the central portion, as will be explained later. This is said to be necessary to solve problems such as image misalignment.

As mentioned above, in order to obtain the speed difference between the center and both ends of the nip portion, the nip shape should be obtained like the portion N surrounded by curves C and 01 in FIG. 11. is considered good.

Then, as mentioned above, set the speed of the end part of the paper to be higher than that of the center valve, pull both sides of the paper, and nip the paper between the two rollers to fix the paper. By doing so, it is possible to maintain the fixation of the image in a good state, and also to prevent the occurrence of wrinkles on the paper.

(Problems to be solved by the invention) However, in the conventional device as described above,
There is a problem in that the rubber layer coated around the pressure roller is deformed by the heat from the heating roller, and the shape of the nip changes.

When the shape of the nip between both rollers of the fixing device changes, the speed distribution in the width direction of the paper changes, and the change in speed changes greatly as shown in song 1i1C2 in Figure 11. Then, the speed at the center becomes much slower than the speed at both sides. Then, the central portion of the paper is greatly curved, and a situation occurs in which the curved portion comes into contact with the heating roller 5.

Further, the toner image is transferred to the heating roller 5 which is heated to a high temperature, and the toner transferred to the roller is transferred to another portion of the paper, which may cause so-called image misregistration.

In a general heating roller type paper conveyance device, when the fusing operation is performed with the paper in contact with the entire width of the roller, the shape N of the nip shape for the paper can be maintained constant. However, when fixing narrow paper, the pressure roller is locally cooled, so the nip shape N tends to change easily.

This is illustrated in FIG. In other words, the same figure (
As shown in the graph a), when fixing a large size paper with a width of W2, the surface temperature of the pressure roller decreases uniformly over the entire length of the paper, but as the width increases When paper of small size Wl is passed continuously, the width of the paper becomes locally cooled, and the temperature distribution of the roller becomes extremely uneven.

Then, due to the change in the temperature distribution of the pressure roller, the pressure roller has an uneven profile as shown in FIG. 3(b). In this way, when the pressure roller is deformed, the nip shape formed by the pressure roller and the heating roller becomes the shape shown as nip shape N.1 in FIG. For the paper P that is nipped between the pressure roller and the heating roller having such a shape, the speed is particularly high in the wide parts on both sides, and the speed in the center part is extremely slow. act.

When a large-sized sheet of paper is passed through the nip section having the shape described above, the difference in speed in the width direction of the sheet becomes very large. In the front part, arcuate wrinkles called bowing pa occur in the width direction of the paper. This problem is gradually amplified as the paper runs, resulting in the formation of horizontal wrinkles on the copy.

On the other hand, when large size paper is being fixed continuously, the temperature distribution in the length direction of the pressure roller does not change significantly, so as shown in Fig. 13(a). In addition, the temperature distribution in the length direction of the roller becomes almost uniform.

Therefore, the shape (profile) of the pressure row 510 becomes as shown in FIG. The ideal shape can be maintained. Then, as shown in FIG. 3(d), the paper P passes through the fixing device.
Copies in good condition can be obtained without wrinkles or the like.

In addition, when fusing large-sized paper after successively fusing small-sized paper as in the case of a conventional fixing device, the shape of the nip N between both rollers should be adjusted to the ideal state. In order to approach this, it is necessary to use means such as allowing the fixing device to run idly for a while, resulting in problems such as a decrease in the efficiency of producing the recording paper.

Furthermore, the profile of the pressure roller as mentioned above is
In addition to being deformed by the temperature distribution in the axial direction of the roller, in a fixing device capable of fixing a wide sheet of paper, the heating roller is configured to be long. Therefore, the accuracy of the profile of the heating roller and pressure roller directly affects the running condition of the paper, which is an extremely difficult issue not only in terms of thermal disturbances but also in terms of device manufacturing technology. .

On the other hand, it has also been proposed to provide a backup roller so as to apply a pressing force from the rear of the pressure roller toward the nip portion. However, when using a means to press the pressure roller using another roller, problems such as scratching the surface of the pressure roller are likely to occur, and the equipment There is also the problem that it becomes complicated.

(Objective of the Invention) The present invention eliminates the drawbacks of the heating roller type fixing device as described above. It is an object of the present invention to provide a device that can maintain the nip shape in a constant state in response to problems that may occur.

(Means and effects for solving the problem) The fixing device of the present invention has a heating roller and a pressure roller arranged in parallel,
It is configured to apply a constant contact pressure between both rollers and to perform fixing by passing a sheet carrying a toner image between both rollers. Further, regarding a device in which a pressure roller that rotates in correspondence with the heating roller is constructed by providing a rubber layer around a pipe, a change in the heat distribution state of the pressure roller causes a cross section of the pressure roller to A correction means is provided to bring the nip shape closer to the set condition when the shape changes.

The pressure roller of the present invention has a structure in which a shaft is disposed inside a pipe, the shaft and the pipe are connected at the center of the roller, and a load is applied only to the center of the pressure roller.

Furthermore, in order to add a control function, a mechanism is provided for pressing the pipe and the shaft separately toward the heating row, and this mechanism constitutes a means for correcting the nip shape, and pressurizes the pipe and shaft. Pressure can be applied independently to the center of the roller.

Further, in order to set the nip shape, cooling air blowing means are provided at both ends of the pressure roller, and a detection device is provided for detecting the distribution state of the surface temperature of the pressure roller, It is also possible to use means for cooling the vicinity of both ends of the pressure roller.

Therefore, in the fixing device of the present invention, even if the temperature at the center of the pressure roller decreases and the nip shape changes, for example when small-sized paper is passed continuously, the pressure roller Since a large pressing force can be applied from the central portion, changes in the nip shape can be minimized, making it possible to prevent wrinkles and the like from forming on the paper.

Further, even if the pressure roller of the fixing device of the present invention is provided with means for pressing at the center, the mechanism does not become particularly complicated, and it is easily compared to the pressure roller of the conventional fixing device. It can be easily installed and the nip pressure can be easily set.

Furthermore, if the pressure roller is configured so that both ends can be cooled, it becomes possible to easily control the 1 degree distribution in the length direction of the pressure roller, making it possible to continuously reduce the This makes it possible to prevent the nip shape from changing even when paper of the same size is passed through the nip.

(Example) The configuration of the fixing device of the present invention will be described according to the illustrated example. The fixing device 1 of the present invention, as shown in FIG. Only the mechanism of the device will be described below.

In the embodiment shown in FIGS. 1 and 2, the heating roller type fixing device 1 includes a heating roller 5 that houses a heat generating lamp therein, as in the case of a conventional heating roller. Both ends of the heating row 55 are supported by the main body frame via bearings 3.3.

Pressure roller 1 arranged corresponding to the heating roller 5
0 has rubber Ji111 on the surface as shown in Figure 2.
A shaft 15 is arranged in parallel inside a pipe 12 provided with a pipe 12, and a piece member 16 is provided between the shaft and the pipe.

The piece member 16 is fixed to the center of the shaft 15 and is provided so as to be fitted into the pipe 12. Then, pressurize the row 510 at the center of the pipe 12.
The pressure roller is supported through shaft bearings 17.17a at both ends of the shaft 15 provided with the piece member 16. Ru.

With the configuration described above, when pressing forces f2, f2 are applied to the pressure roller of the present invention from both sides of the shaft, as shown in FIG. 2a, the pressing force is The pressing force f1 is applied toward the center of the pressure roller, and the pressing force f1 acts on the heating roller from the center of the pressure roller.

Therefore, in the fixing device of the present invention, when pressure and force are applied to the pressure roller 10 from both sides of the shaft 15 toward the heating roller 5, as in the case of the conventional fixing device, A particularly strong pressing force is not applied to both end portions of the nip portion.

By configuring the fixing device 1 as described above, when continuously fixing sheets of the same size, the deformation of the pressure roller profile is corrected as shown in FIG. The pressure row 510 is pressed toward the heating roller 5 from its center.

That is, pressing forces f2 and f2 are applied to the heating roller 10 from both ends of the shaft, but this force is applied to the central portion of the pressure roller, so that the pressure roller 10 is As shown in FIG. 2, the heat roller 5 acts strongly on the central portion of the heating roller 5.

On the other hand, the heating roller 5 has the pressure roller 510
Since reaction forces F and F act on both ends of the shaft in response to the pressing force from The vehicle is set to a state suitable for driving.

Further, when fixing large size paper after successively fixing small size paper, the profile of the pressure roller is naturally modified. However, the pressure roller 1 of the present invention
0 is configured so that a pressing force is applied at its central portion, and therefore, the pressing force f1 acts at the central portion of the nip shape where the central portion is extremely narrow.

Therefore, since an action is applied to automatically return the deformed nip shape to its normal shape as described above, the nip shape N suitable for running large-sized paper can be easily restored. becomes.

As described above, in the fixing device of the present invention, by supporting the pressure roller through the shaft, even when the paper size changes, it is possible to move paper of various sizes. This can be done in good condition, and it is possible to prevent wrinkles from occurring on the paper.

(Embodiment 2) In the heating roller type fixing device of the present invention, in addition to configuring the pressure roller as shown in FIG. 2, a pressure roller is configured as shown in FIGS. A pressure roller can be configured.

In another embodiment of the present invention, the pressure roller 10 is provided with a rubber layer 1 on the surface of the pipe 12, as shown in FIG.
1, and a shaft 12 at both ends of the pipe 12.
a is provided to protrude, and the shaft 12a is supported by a bearing 13.

Further, a shaft 15 is disposed so as to penetrate inside the pipe 12, and is supported by bearings 17, 17a disposed at both ends of the shaft 15.

Furthermore, a block member 16 is provided at the center of the shaft 15, and the shaft 15 and the pipe 12 are connected to each other.
The structure is such that rotation is performed integrally via the .

The pressure roller 10 of the present invention configured as described above is
As shown in FIG. 4, when assembled as a fixing device, the roller 10 is supported by two bearings on each side, and each bearing is supported by a spring or other means. It is possible to apply a pressing force by That is, in the illustrated embodiment, one
In one stroke, it is configured to be able to apply a pressing force fa to the pipe bearing 13 and apply a pressing force fb to the shaft bearing 17, respectively.

For example, as a method of supporting the shaft of the pressure roller 10,
As shown in the figure, it is also possible to arrange the shaft bearing support member 21 to be slidable with respect to the pipe bearing support member 20, and to press the two bearing members with one urging means. .

When configured as described above, the cam member 22 is arranged between the two bearing members 20 and 21, and by rotating the cam 22 by the shaft 23, the shaft Bearing support member 2
You can set an interval of 1.

The cam may be driven by having the operator manually rotate the cam shaft, for example, when passing large size paper after successively passing small size paper, or Any means can be used, such as performing the control operation according to a program set in the control device of the image forming apparatus.

As described above, by configuring the pipe bearing 13 and the shaft bearing 17 to be supported by one bearing or unit, the pressure roller is supported by two
This makes it possible to easily adjust the pressing force on the two shaft members.

With the pressure roller support means of the present invention, the distribution of the pressing force of the pressure roller 10 against the heating roller 5 can be easily corrected, as shown in FIGS. 6 and 6a.

That is, as shown in FIG. 6, the pipe bearing 13
When setting the relationship between the pressing force fa applied to the shaft bearing 17 and the pressing force fb applied to the shaft bearing 17 to be fa>fb,
The pressing force at the nip portion between both rollers is weak at the center and strong at both ends, resulting in a nip shape that is tapered in the middle, as shown by nip shape N.

On the other hand, when setting the relationship fB<fb,
Since the supporting force at the central portion of both rollers is increased, the bending distance of the pressure roller 10 is reduced, and the shape of the nip shape N becomes medium thick.

Then, as described above, by adjusting the pressing force between both ends and the center of the pressure roller, the nip shape is changed to control the movement state of the paper, and the center and both ends of the paper are controlled. By making it possible to set the speed difference between the fixing section and the fixing section in accordance with the size of the paper, it is possible to prevent the occurrence of wrinkles or the like on the paper to be fixed.

(Embodiment 3) In the above-described fixing device of the present invention, the structure of the pressure roller is improved in order to adjust the nip shape, and the pressing force against the shaft of the roller can be adjusted. However, in the fixing device of the present invention, as shown in FIGS. 7 and 8, it is also possible to adjust the profile of the pressure roller by providing a cooling means for the pressure roller. .

In the embodiment shown in FIG. 7, the pressure roller 10
Sensors 27 and 27a are provided for detecting the temperature of the center, end, and rollers. This sensor is input to the temperature comparator circuit of the controller and
- It is possible to detect the temperature distribution in the length direction of the wire.

In this embodiment, for the pressure roller 10,
Fans 25.25a are provided near both ends thereof.

It is desirable that these fans 25 and sensors 27 be arranged in the relationship shown in FIG. It is possible to provide the

In the fixing device 1 configured as described above,
When small-sized paper is passed through continuously, the temperature of the pressure roller 10 becomes lower at a portion corresponding to the width W1 of the small-sized paper, and the nip shape changes, as explained in FIG. Suitable for small size paper due to variable size. However, if a large size sheet is passed through a replica made by continuously running a large number of small size sheets, wrinkles and the like may occur.

Therefore, in the fixing device of the present invention, the pressure roller 10
The fan 25.25a is configured to operate when the temperature difference detected by the two sensors 27.27a provided for the fan 25.25a exceeds a certain value.

Then, both ends of the pressure roller are cooled by air blown from a fan, so that the temperature difference in the width direction of the paper is within a certain range, as shown in FIG. 13(a). i, II tll operations can be performed.

Furthermore, in a fixing device equipped with a fan as described above, the easiest means to use is to suck fresh air from outside the device and blow it onto the pressure row of the fixing device. In addition, it is also possible to reduce the temperature inside the housing by exhausting the high temperature air inside the fixing device to the outside.

(Effects of the Invention) The fixing device of the image forming apparatus of the present invention has the above-described configuration, and the roller of the present invention can be easily incorporated in place of the pressure roller of the conventional fixing device. The entire structure of the fixing device will not be changed.

Therefore, in the fixing device of the present invention, even if the temperature at the center of the pressure roller decreases and the nip shape changes, for example when small-sized paper is passed continuously, the pressure roller Since a large pressing force can be applied from the central part, changes in the nip shape can be minimized, and wrinkles etc. can be prevented from occurring on the paper.

Further, even if the pressure roller of the fixing device of the present invention is provided with a means for pressing at the center, the mechanism does not become particularly complicated, and it can be easily incorporated into the pressure roller of a conventional fixing device. It is also possible to easily set the nip pressure.

Furthermore, if the pressure roller is configured so that both ends can be cooled, it becomes possible to easily control the humidity distribution in the length direction of the pressure roller, making it possible to continuously Even when paper of the same size is passed through, changes in the nip shape can be prevented.

[Brief explanation of drawings]

FIG. 1 is a front view of the fixing device of the present invention, FIG. 2 is a sectional view of the pressure roller, FIG. 2a is an explanatory diagram of the state in which pressing force is applied to the pressure roller, and FIGS. 3 and 3a are , FIG. 4 is a front view of another embodiment of the fixing device of the present invention, and FIG. 5 is a cross-section of the pressure roller shown in FIG. 4. Figure, 5a
The figures are explanatory diagrams of the support means for the pressure roller, Figures 6 and 6.
Figure a is an explanatory diagram of the relationship between both rollers of the fixing device and the nip shape, Figure 7 is a front view of another embodiment of the present invention, Figure 8
The figure is a side view, FIG. 9 is an explanatory diagram showing the main parts of a general image forming apparatus, No. 10 is a sectional view of a conventional heating roller type fixing device, and FIG. 11 is a cross-sectional view of a conventional heating roller type fixing device. 12 and 13 are explanatory diagrams showing the relationship between the temperature of the pressure roller and wrinkles generated on the paper, respectively, and FIG. 12 and FIG.
3, (a) is a graph of the temperature distribution state in the length direction of the pressure roller, (b) is an explanatory diagram of the roller profile, (C) is an explanatory diagram of the nip shape N, and (d) is a graph of the paper FIG. 2 is an explanatory diagram of the running state of the vehicle. Reference numeral 1 in the figure: fixing device, 5: heating O-ra,
10... Pressure roller, 11... Rubber layer, 12... Pipe, 15... Shaft, 16... Piece member, 20・21・・・・・・
Bearing member, 22...cam, 25...fan, 27...sensor, 30...photosensitive drum, 35...conveyor belt device, 36.
...Guide board. 1 Figure 2 Figure 4 Figure 5 Figure 5α! j Figure 12 ((b) (C-cd)

Claims (4)

[Claims] (1) A heating roller and a pressure roller are arranged in parallel, a constant contact pressure is applied between both rollers, and a sheet carrying a toner image is passed between the two rollers to perform fixing. In a fixing device configured by providing a rubber layer around a pipe and a pressure roller that rotates in correspondence with the heating roller, the pressure roller may rotate due to a change in the heat distribution state of the pressure roller. 1. A fixing device for an image forming apparatus, characterized in that a fixing device for an image forming apparatus is provided with means for bringing the nip shape closer to a set condition when the cross-sectional shape of the fixing device changes. (2) Image formation according to claim 1, characterized in that means for applying pressure to the center of the pressure roller is provided as a means for preventing an adverse effect on the nip shape. Equipment fixing device. (3) Place the shaft inside the pressure roller pipe,
The shaft and the pipe are connected through a block member at the center of the roller, and a mechanism is provided for separately controlling the pressing force toward the heating roller for the pipe and the shaft. A fixing device for an image forming apparatus according to claim 2. (4) As a means for correcting the nip shape, a means for blowing cooling air to both ends of the pressure roller is provided, and a detection device for detecting the distribution state of the surface temperature of the pressure roller. 2. The fixing device for an image forming apparatus according to claim 1, further comprising: a fixing device for an image forming apparatus according to claim 1, wherein the fixing device is provided with a pressure roller so as to cool the vicinity of both end portions of the pressure roller.