JPH01185579A - Pressure roller device in fixing device - Google Patents

Abstract

PURPOSE:To execute a fixation to a large-sized paper in a satisfactory condition by forming a shape in which a sagging part is not generated in a condition in which a pressure roller is heated. CONSTITUTION:A pressure roller 30 of a fixing device 15 is composed of a small diameter part formed in a both-edge vicinity, a large diameter part formed in a central part and an inflection point to connect the small diameter part and large diameter part in a room temperature, and by heating the pressure roller 30 in the using condition of the fixing device 15, an ideal nip shape is made. Thus, the action of the fixation to the large-sized paper can be executed in the satisfactory condition, simultaneously, the generations of a paper wrinkle, etc., can be prevented, and a copy with a good quality can be obtained.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is directed to a heating roller type fixing device that prevents the formation of paper wrinkles on the paper that is nipped between the rollers of the fixing device. In particular, the equipment that enables
The present invention relates to a device configured such that the surface shape of a heated pressure roller becomes an ideal nip shape when a fixing device performs a fixing operation.

(Prior Art) In conventional devices using dry toner, such as fusuma copying machines and printers, a toner image formed on a photoreceptor drum is transferred to paper, and the paper carrying the unfixed toner image is
A means is used in which the toner is guided to a fixing device by a conveying means, the toner is melted by applying heat or pressure in the fixing device, and the toner is fixed by means such as pressing it against the paper to complete the copy. .

Generally, a heating roller type fixing device is often used to fix the unfixed toner image as described above. In this heating roller method, a heating roller with a built-in heating lamp, etc., and a pressure roller, which is pressed with a predetermined pressure against the heating roller, are arranged facing each other. The paper is nipped between both rollers so that heating and pressing can be performed.

For example, as an in-shell copying machine, an apparatus having a structure as shown in FIG. 4 is used. This copying machine 1 is configured to have a platen 2 on the top surface of its main body so that a document can be placed thereon, and the image of the document set on the platen 2 can be
The image is scanned by the image reading device 3 and the image information is transmitted to the photosensitive drum 5.

Various devices such as a developing device RA 7, a charging corotron 6, a transfer and peeling corotron 8, and a cleaning device 9 are arranged around the photosensitive drum, and the surface of the photosensitive drum is coated with light from the image reading device. By forming an electrostatic latent image and supplying toner from a developing device to the electrostatic latent image, it is visualized as a toner image. Then, the toner image on the photoreceptor drum is transferred to the paper by electric discharge from the transfer/peeling corotron 8.
Thereafter, the toner remaining on the photosensitive drum is removed by a cleaning device 9.

Further, the paper to which the toner image is transferred is supplied from the paper feeder, and while passing through the paper conveyance path, the toner image is transferred from the photoreceptor drum 5 at the image transfer portion by discharge from the transfer/peeling corotron as described above. is transcribed. Then, the paper carrying the unfixed toner image is guided to the fixing device 15 by the conveyor belt device 10.

In the above-described copying machine, the heating roller type fixing device M15 that is generally used includes a heating roller 20 that is rotatably supported by a frame 25 via a bearing 24, as shown in FIG. and a jπ1 pressure roller 30 configured to be pressed against the heating row 520 with a predetermined pressure by a spring 36.

Further, the pressure roller 30 has a cylindrical core 3 made of metal.
1 and a covering layer 32 of an elastic material such as rubber formed on the surface thereof.
The bearings 35 provided at both ends are configured with pressing means using springs 36, respectively, and the springs 35 are set to press a predetermined pressure C through the bearings. A means for adjusting the nip pressure and nip shape is used.

This heating roller 20 is provided with a heating element 23 such as a halogen lamp inside the hollow part of the roller core, and the surface of the heating roller 520 is heated to a predetermined temperature (180°C to 200°C) by the heat of the lamp 23. ), the heat melts the toner carried on the paper, and the pressure from the pressure roller presses the melted toner onto the paper to fix it.

Both rollers have the above-described configuration, and the shape of the nip portion of each roller is such that the heating row 520 is wide on both sides and narrow in the center, as shown in FIG. 6(a). In contrast, as shown in FIG. 3B, a pressure roller 30 is formed with a coating layer 32 made of an elastic material such as rubber adhered to the surface of a core 31. There is.

Therefore, the nip shape N between the two rollers is set to almost match the shape of the nip portion of the heating roller, as shown in FIG. 14(C), and the nip shape N
This allows the fixing device to properly hold and convey the paper and fix the paper.

(Problems to be Solved by the Invention) However, in the case of the conventional fixing device as described above,
A commonly used small copying machine or A3
In copying machines and the like that use paper smaller than this size, the rollers are relatively short, and maintaining a constant nip pressure can be easily set from the viewpoint of the rigidity of the roller itself.
The shape of the nip portion can also be arbitrarily set by pressing with a spring.

On the other hand, in large copiers that make copies using large-sized paper such as AO size, the width of the fixing device is very large, corresponding to the paper size, and the width of the fixing device is very large. - The length of the radius becomes very large compared to its diameter.

As shown in FIG. 7(a), the pressure roller 30 in the fixing device of a large copying machine as described above is manufactured so that its outer diameter is constant. When the fixing device is used, the metal core member 31 and the elastic body 32 are heated by the heat generated by the heating roller. In this case, for example, the pressure roller 30 is
When heated to 60° C., the core member 31 and the elastic body have different coefficients of thermal expansion, and the coefficient of thermal expansion of the elastic body 32 becomes larger than that of the core 31.

However, as shown in FIG. 3B, since the elastic body 32 is integrally bonded to the surface of the core 310, the elastic body 32 has a large IIJIH coefficient while the core 31 has a small expansion coefficient. Since the bonded part does not stretch, due to its internal strain, the outer diameter is not the same throughout, but the center part swells greatly and the sagging part 33 is formed at both ends. becomes. The state has a shape as shown in FIG. 3(C).

In other words, when the fixing device is not heated, the outer diameters of the two rollers, the heating roller 20 and the pressure roller 30, are formed as shown in FIG. The nip shape N4 in between is as shown in FIG. 4(b).

Due to the above-mentioned nip shape N4, the conveyance speed for the paper at $4 is such that the center is fast and the both ends are slow, as shown in FIG.

Therefore, when a sheet of paper is passed through the fixing device in a state where the fixing device is not heated, as shown in FIG.
It is possible to guide the paper in a good condition and prevent the occurrence of vertical wrinkles on the paper.

However, in the fixing device configured as described above, when the heater of the heating roller 2o is energized and heated, the pressure roller 30 is heated by the heat, and each member of the heating roller 30 is heated. When expansion occurs, although the shape of the heating roller 520 does not change significantly, the pressure roller 30 has a sagging portion 33 as shown in FIG. 9(a) due to the uneven thermal expansion as described above. will be formed. As a result, the nip shape N3 formed between the two circles has inflection points h1 and h2 on the inside of both ends, as shown in FIG.
Both 1111I end portions are formed so as to be nipped with a narrow width.

Therefore, due to the nip shape N3 between both rollers as described above, the curve S of the paper conveyance speed is
3 is formed in a complicatedly bent state, as shown in FIG. 3(C). Then, according to the speed curve shown in the same figure (C), the inflection point h1 at the center and both sides
~ h3 affects the conveyance of the paper, and as shown in the same figure (d), an inconvenient state occurs such as the occurrence of paper wrinkles Pa centered on the inflection points h1 and h2 on both sides. , many problems occur such as not being able to obtain a copy in good condition.

(Purpose of Application) The present invention solves the drawbacks of conventionally used devices as described above.The present invention improves the shape of the pressure roller of the constant @ device, and the pressure roller is in a heated state. It is an object of the present invention to provide an apparatus that can perform a fixing operation on large-sized paper in a good condition by forming the fixing device in a shape that does not cause drooping.

(Means and operations for solving the problems) The pressure roller device in the fixing device of the present invention transfers the toner image formed on the photoreceptor drum onto paper, and transfers the paper carrying the toner image to the conveyor belt device. In an apparatus configured to transport the material by a heating roller type fixing device, the fixing device is nipped between both rollers of a heating roller type fixing device, and is heated and pressurized to perform fixing. , consisting of a small diameter part formed near both ends, a large diameter part formed in the center, and an inflection point connecting the small diameter part and the large diameter part, and the pressure roller is used in a fixing device. This device is designed to create an ideal nip shape by heating the nip in the same state.

Further, in the device of the present invention, the pressure roller includes a metal core portion and an elastic body coated around the core, and by changing the coating thickness of the elastic body, The small diameter part near the center, the large diameter part with a uniform diameter near the center, the part slightly larger in diameter than the small diameter part at both ends, and the different diameter parts of each of these through the inflection point. It is configured so that it can be connected.

By configuring as described above, in the fixing device of the present invention, the outer diameter shape of the pressure roller is configured by a large diameter portion, a small diameter portion, and an inflection point connecting them. When the pressure roller is heated,
The nip shape formed by the heating roller and the pressure roller becomes ideal, so that the fixing operation for large-sized paper can be performed in good condition, and the occurrence of paper wrinkles etc. can be prevented. This allows you to obtain high-quality copies.

(Example) The configuration of the pressure roller device in the fixing device of the present invention will be described according to the illustrated example.

The fixing device of the present invention, as in the conventional example shown in FIG. This device is composed of a pressure roller arranged to be pressed with a predetermined pressure by means.

As shown in FIG. 1(a), the pressure roller 30 of the present invention is configured so that each portion has a different diameter. d the diameter of
3. The diameter near both ends is set as d2, and the portions with different outer diameters are connected at inflection points h1 and h2 to form a smooth curve. Further, the diameter d3 at both ends and the diameter d2 of the small diameter portion may be formed between the paths.

In reality, fixing 1↑] is approximately 90 cm long,
A portion d1 of approximately 70 cm in the center has approximately the same diameter.
Approximately 10 cts from both ends to the inside
The inflection points hl and h2 are set at the inflection point, and the small diameter section d2 is set at the inflection point. Also,
In the pressure roller of the present invention, the core portion is formed as a member with a uniform diameter, and can be formed into the above-mentioned shape by changing the thickness of the elastic body covering the core portion. It is made possible.

In other words, in a pressure roller constructed in the same way as a conventional pressure roller, the outer diameter of the roller is approximately 80a11φ, but the diameter d1 of the large diameter portion and the diameter d2 of the small diameter portion are The difference is formed to be approximately 0°2aw to 2am+. Therefore, at the inflection points h1 and h2, the difference in diameter as described above is connected by a smooth curve, and when the heating roller 30 is heated, the outer diameter shape of the row 530 is the same as that conventionally used. It can be constructed so that droop does not occur at the end, as is the case with heating rollers.

Furthermore, as shown in FIG. 1(b), the heating roller 20 disposed opposite the pressure roller 30 described above is configured similarly to a conventional heating roller, and there is a gap between the two rollers. By nipping the paper between the rollers, the paper carrying the unfixed toner image is conveyed in a good condition so that the fixing operation can be performed.

The embodiment shown in FIG. 2 shows a case where a sheet is passed through the fixing device 15 of the present invention without heating. In the cold state of the fixing device shown in FIG.
- The roller 20 and the pressure roller 530 are shown in the same figure (a), respectively.
As shown in (b) of the same figure, since the roller shape is initially set to the shape at the time of manufacture, the nip shape N2 formed by those two rollers is the inflection point of the pressure roller, as shown in (b) of the same figure. The nip is bent at portions corresponding to h1 and h2, and is formed to have a shape slightly different from the ideal nip shape.

Furthermore, depending on the nip shape described above, the conveying speed diagram at the nip portion is such that the speed changes at positions corresponding to each portion of the roller 30, as shown by 82 in FIG. , the speed is set so that the overall speed gradually increases from the center toward both ends.

Therefore, when conveying paper with the fixing device f15 in the cold open state, as shown in FIG. As a result, the paper passes through the nip portion in good condition.

Furthermore, when the fixing device of the present invention is set to the heating state, as shown in FIG. The state shown in FIG. 5(a) is reached, and the row 53
Unlike the conventional example, drooping portions 33 as shown by chain lines do not occur at both ends of the wire. Therefore, as described above, the nip shape N1 formed by the two rollers is as shown in FIG. is formed.

When the nip is formed in the above-mentioned shape, as shown at 81 in FIG. The force applied to the paper when the paper P is nipped between both rollers of the fixing device and fixed as shown in FIG. Similarly, it is in a state where it is slightly pulled on both sides, and the sheet can be guided well.

As described above, in the fixing device of the present invention, by specifying the outer diameter shape of the pressure roller, even when performing a fixing operation on a wide sheet of paper, the sheet can be transported well. Therefore, it is possible to prevent vertical wrinkles from occurring on the paper, and the fixing function can be performed satisfactorily.

In the fixing device of the present invention described above, the shape of the pressure roller is such that, as shown in FIG. The basic structure is to form parts with different diameters into a shape that smoothly connects them, and the outer diameter of each part depends on the properties of the elastic material such as rubber used for the pressure roller, and other physical conditions.

(Effects of the Invention) Since the device of the present invention has the above-mentioned configuration, it is possible to fix the fixing device between both rollers in the fixing device of a large-sized copying machine that copies large-sized paper. It becomes possible to set the nip shape to a shape that can prevent wrinkles from occurring on the paper.

In addition, the fixing device of the present invention can carry out the conveyance action on the paper in good condition, and does not cause wrinkles or the like during the fixing operation even on thin and stiff paper. , it is possible to perform the action of fixation.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of each roller of the fixing device of the present invention, in which (a) is a side view of the pressure roller, (b) is an explanatory diagram of the shape of the heating roller at the nip portion, and FIG. FIG. 3 is an explanatory view of the fixing device of the present invention in a cold open state and a heated state, respectively. In the above two figures, (a) is an explanatory view of the shapes of the heating roller and the pressure roller, and (b) is an explanatory view of the shapes of the heating roller and the pressure roller. is an explanatory diagram of the nip shape, (C) is a speed diagram, (d) is an explanatory diagram of the state of the paper nipped in the fixing VA position, Fig. 4 is an explanatory diagram of a general copying machine, and Fig. 5 is an explanatory diagram of the nip shape. is a sectional view of the fixing device, Figure 6 (
(a) is an explanatory diagram of the shape of a conventionally used heating roller, (b) is an explanatory diagram of a pressure roller, and (C) is an explanatory diagram of the nip shape between both rollers in the conventional example. Figure, 7th
Figure (a) is a side view of a conventional heating roller, Figures (b) and (C) are explanatory diagrams showing the state of the expansion fan when the pressure roller is heated, and Figures 8 and 9. are explanatory diagrams of the roller and nip state in a conventional fixing device. In these two diagrams, (a) is an explanatory diagram of the outer diameter shape of the heating roller and pressure roller, and (b) is an explanatory diagram of the nip shape. FIG. 2C is a speed diagram, and FIG. 1D is a diagram showing the conveyance state of the paper. Reference numeral 1 in the figure: Copying machine, 5: Photoreceptor drum,
15... Fixing device, 20... Heat roller, 23... Lamp, 30... Pressure roller, 36... Spring. Figure 2 Figure 3 Figure 8 Figure 9

Claims (2)

[Claims] (1) The toner image formed on the photoreceptor drum is transferred to paper, and the paper carrying the unfixed toner image is conveyed by a conveyor belt device, nipped between a heating roller and a pressure roller, and heated. In the apparatus configured to perform fixing by applying pressure to the fixing device, the pressure roller of the fixing device has a small diameter portion formed near both ends, a large diameter portion in the center, and a pressurizing roller of the fixing device at room temperature. The pressure roller is composed of a bending portion connecting a small diameter portion and a large diameter portion, and is configured to have an ideal nip shape by heating the pressure roller when the fixing device is in use. A pressure roller device in a fixing device featuring features. (2) Where the pressure roller is composed of a metal core portion and an elastic body coated around the core portion, by changing the coating thickness of the elastic body,
A small diameter part near both ends, a large diameter part with a uniform diameter in the center, a part slightly larger than the small diameter part at both ends, and these different diameter parts are connected via an inflection part. A pressure roller device in a fixing device according to claim 1, characterized in that it is configured as follows.