JPS60227276A - Fixing device for wet type electrophotographic copying machine - Google Patents

Abstract

PURPOSE:To provide improvement in fixing efficiency to a sheet, reduction in size of a device and improvement in image quality by providing here and there plural projecting parts having the surface area of a specific value or below to sheet press rollers of a fixing device for a wet type electrophotographic copying machine. CONSTITUTION:The sheet S which is fed by a conveying plate 2 is fixed thereon with an image while said sheet is conveyed by the sheet press rollers 3 and a heating roller 4 for conveying the sheet which face each other by holding the sheet in place in a feed path. Each sheet press roller 3 is constituted by being provided here and there with the plural projecting parts set at <=(50X50)mum<2> surface area per unit area on the surface thereof. The sheet S is brought into tight contact with the peripheral surface of the roller 4 by the rollers 3 and is heated by the roller 4 heated by a halogen lamp 4A contained therein, by which the image is fixed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a fixing device, and more particularly to a fixing device for heat-fixing an image visualized using a wet developer.

(Prior art) Toner particles contained in a wet developer adhere to an electrostatic latent image on a photoreceptor by electrophoresis, and then are transferred to, for example, a recording paper (hereinafter referred to as a sheet). The solvent that has permeated the sheet or the solvent in the image is evaporated and dried, thereby fixing it on the sheet.

For fixing images using such a wet developer.

It is provided on the unfixed image bearing surface side of the sheet.

A hot plate method includes a presser roller that is rotationally driven in the direction of conveyance of the sheet, and a hot plate with a built-in heat source that faces the two rollers with a gap and forms a conveyance path for the sheet. , a roller pair method was used in which a pair of rollers were provided in contact with each other, and the roller that contacted the back side of the image bearing surface of the sheet was configured as a heating roller, but in each of these fixing devices, a hot plate method was used. Due to the thickness of the sheet, the heat transfer ratio to the image surface is not uniform, which may prevent the solvent from evaporating and drying sufficiently.Also, when performing single-sided copying, the image surface after fixing may not be on the hot plate. This movement causes the toner particles in the image that are in contact with the hot plate to re-melt, and in this state, the softened toner particles are rubbed off.

As a result, a double-sided copy with good image quality could not be obtained.

Furthermore, since the presser roller only has the function of directing the sheet toward the hot plate and is not designed to bring the sheet into close contact with the hot plate, there is a drawback that the image fixing efficiency on the sheet is poor.

On the other hand, the pair-of-roller type has the disadvantage that because the roller and the image are always in contact with each other, the image is easily transferred to the circumferential surface of the roller.

Therefore, in order to eliminate such drawbacks, the inventors of the present invention have developed a heat source that has a built-in heat source and is disposed on the surface of the roller on the side of the unfixed image bearing surface of the sheet.

We proposed a configuration in which multiple extremely fine protrusions are scattered, but this configuration has the risk of reducing heat transfer efficiency because the area of the roller circumferential surface that comes into contact with one image area is extremely small. Therefore, it was necessary to increase the contact time between the sheet and the roller.

Therefore, without satisfying these conditions, a conveyor belt is used as a means to feed the sheet while pressing the sheet against the roller, and the conveyor belt is surrounded by the roller circumferential surface. However, such a configuration has a new drawback in that the apparatus, particularly the sheet conveyance device of the fixing section, becomes large in size.

(Objective) The present invention has been made in view of the above-mentioned problems, and its object is to provide a fixing section M that eliminates the above-mentioned drawbacks.

(Structure) According to the present invention, a 50×
A plurality of protrusions each having a surface area of 50 μm or less are scattered, and the surface is placed opposite the surface of the sheet presser roller, and has a surface that has a larger contact area with the sheet than the sheet presser roller. A sheet conveying means is provided which cooperates with the sheet pressing roller and heats the sheet from the back side of the unfixed image bearing surface of the sheet.

The present invention will be explained below with reference to illustrated embodiments.

FIG. 1 shows an example in which a heating roller is used as the sheet conveying means facing the sheet pressing roller.

In FIG. 1, a conveyance plate 2 is provided at the entrance of a fixing section 10 to feed and guide a sheet s from a developing section (not shown) to the fixing section 1.

The fixing unit 1 includes a sheet pressing roller 3 facing each other across the feeding path of the sheet S fed by the conveying plate 2, a heating roller 4 for sheet conveying, and a sheet pressing roller on the feeding path. 3, a cleaning roller 5 that is in contact with the circumferential surface of the heating roller 4, and a cleaning blade 6 that is in contact with the circumferential surface of the heating roller 4 for conveying sheets; The sheet separating member 7 includes a sheet separating member 7 and a sheet discharging plate 8.

In FIG. 1, reference numeral 9 denotes the heating roller 4 for sheet conveyance.
This is a temperature sensor that detects the surface temperature of.

The sheet pressing roller 3 moves the sheet S along the feeding direction.
At least one or more protrusions (two in one figure) are arranged side by side, and a plurality of protrusions each having a surface area of 50×50 μm 2 or less are scattered on the surface thereof.

The protrusion on the surface of the sheet pressing roller 3 is a second
As shown in Figure (Al), a large number of alumina powders 3c are glued onto the base material 3a with a large number of alumina powders 3c scattered through the adhesive 3b applied on the roller base material 3a, and the alumina powder 3c The surface is coated with a binder 3d to prevent peeling.

The protrusions may be formed by knurling the surface of the roller base material 3a and coating the surface with a sprayed layer 3e of stainless steel, silicon carbide, etc., as shown in FIG. 2+B+. There is also.

The sheet pressing roller 3 is configured to press the sheet S in the feeding direction so that the sheet S being conveyed can be brought into contact with the circumferential surface of the sheet conveying heating roller 4 in a surrounding state. The installation location is set, and the sheet S is brought into close contact with the circumferential surface of the sheet conveying heating roller 4 by pressing and biasing the spindle of the roller 3 with a spring (not shown) K. It has become.

On the other hand, the sheet conveyance heating roller 4 is a hollow roller made of aluminum, which is a good thermal conductor, and whose outer peripheral surface is formed smoothly so that the contact area per unit area with the sheet S is larger than that of the sheet pressing roller 3. , has a halogen lamp 4A as a heat source inside, and has the sheet pressing roller 3 described above.
It rotates in cooperation with the The rotation of each of these rollers is performed by selecting one or both of them as appropriate.

The heat roller 4 for sheet conveyance has a built-in heat roller 4A whose temperature is controlled by a temperature sensor 9 so that the surface temperature of the heat roller 4 for sheet conveyance is about 200.degree.

When the sheet S is conveyed to the fixing unit 1 as described above,
The sheet S is brought into close contact with the circumferential surface of the sheet conveyance heating roller 4 by the sheet pressing roller 3, and is held in the so-called state between the two rollers, and is directed toward the discharge section through the cooperative rotation of the rollers. transported.

According to the fixing device as described above, a heat source is provided in the sheet conveying heating roller 4 having a smooth surface that can be manipulated with a large contact area with respect to the sheet as well as the sheet pressing roller 3. On the other hand, since the adhesion of the sheet by the sheet press roller 3 can be improved, the heating area for the sheet can be expanded and the heat transfer efficiency can be improved. Since they are rotated together, when performing double-sided copying, even if the image surface that has been fixed comes into contact with the sheet conveyance heating roller.

During conveyance, the toner particles on the image surface are not rubbed off, so that the image quality is not degraded.

Furthermore, the sheet pressing roller that comes into contact with the unfixed image is
The state of its peripheral surface suppresses the transfer of toner particles in the image, and by providing a plurality of sheet presser rollers, the heating area of the sheet relative to the sheet conveyance heating roller is expanded, so the sheet presser roller The contact pressure between the sheet conveying heating roller and the sheet conveying heating roller does not need to be very large. Therefore, the wall thickness of the sheet conveying heating roller can be reduced and the heat capacity can be reduced, and the temperature rise time of the sheet conveying heating roller can be shortened. It is also possible to do so.

The inventor conducted an experiment on the transfer of the sheet pressing roller described above, and obtained the results shown in FIG. 3.

In FIG. 3, the vertical axis represents the visual discrimination of toner particle transfer, indicating that the degree of discrimination increases upward from the base point, and the horizontal axis represents the contact area of each protrusion with respect to the sheet. This shows that the contact area is set smaller toward the right from the base point.

In FIG. 3, the degree of transfer to the sheet pressing roller changes suddenly at a point where the contact area of the protrusion with the sheet is 50 x 50 μm2, and below this area, almost no transfer of toner particles occurs. It turns out there isn't.

Next, the sheet conveyance means is replaced with the above-mentioned heating roller,
An example constructed using a belt will be explained with reference to FIG. 4 and subsequent drawings.

In the drawings from FIG. 4 onwards, the same members as those shown in FIG. 1 are designated by the same reference numerals.

In FIG. 4, the sheet conveying belt 10 is made of a Ni electroformed belt or a stainless steel belt whose surface that contacts the sheet has the same characteristics as the sheet conveying heating roller 3. It is a good conductor and comes into contact with the sheet press roller 3 in a state that it surrounds a part of the circumferential surface of the sheet press roller 3, and is hooked around the pulleys 11, 12, and 13, and is rotated at the contact portion with the sheet press roller 3. It is configured to move in the feeding direction of the sheet S.

The sheet conveyance belt 10 is being turned! J
11, 12, and 13 are thermally insulating rollers, and one of the pulleys located on the sheet pressing roller 3 side is biased by a spring 14 to move the sheet conveying belt 10.
functions as a tension pulley.

Then, the sheet conveyance belt is hooked around each pulley]
In the internal space formed by
5 and a reflective shade 16, and the belt hook of each pulley is located at the front in the direction of belt movement in the rotating section to remove foreign matter such as dust attached to the back side of the belt, and to prevent foreign matter from entering the rotating section. Cleaning pad 17 that prevents
are placed respectively.

In addition, the belt hook of the pulley is placed on the rotating part, and a cleaning felt 8 for cleaning the surface of the belt is arranged on the surface side of the belt.

Note that in FIG. 4, reference numeral 19 indicates a discharge table for guiding the sheet discharged from the fixing section 1.

In an apparatus using such a belt, the sheet S conveyed to the fixing section 1 is heated by the belt 10 when placed on the sheet conveyance belt 10 which is heated by the thermostatic lamp 15 .

Next, when the sheet S is brought to the contact portion with the sheet pressing roller 3, the sheet S is heated by the sheet conveying belt 10 while being brought into close contact with the sheet conveying belt 10 by the sheet pressing roller 3.

According to the fixing device as described above, 7-1-8 comes into contact with the heated belt before the sheet +-S reaches the opposing portion of the sheet conveying belt and the sheet pressing roller, so that Since it is possible to preheat the sheet S, the heating time for the sheet S can be increased to increase the fixing efficiency.Furthermore, the above-mentioned sheet pressing roller and the sheet conveying belt can work together in the facing section. Therefore, even when fixing both sides of the sheet S, the fixed image will not be rubbed.

Furthermore, if the belt is made of a material with a small heat capacity, the temperature-related start-up time can be shortened.

In addition, in order to suppress the heat radiation loss from the sheet conveying belt 10 described above, as shown in FIG. It is also possible to provide a heat insulating cylinder 20 made of a casing that exposes the side that becomes the transport surface of the sheet S and surrounds the remaining portion.

The heat insulating cylinder 20 includes a heat insulating layer 20A and a mirror-like reflective layer 20B provided on the upper surface of the heat insulating layer 20A, that is, the surface of the heat insulating layer 20A on the side opposite to the sheet conveying belt. The hook is rotated so that the heat rays emitted from the belt 10 extending below the pulley are reflected by the reflective layer 20B, increasing the amount of heat stored in the belt.

(effect) According to the invention, the sheet presser roller cooperates with the sheet presser roller.

In addition, since the sheet is heated by a sheet conveying means that has a larger contact area with the sheet than the same roller, it is possible to improve the fixing efficiency on the sheet, thereby making it possible to downsize the fixing device. Since the above-mentioned two are in a cooperative relationship, when heating and fixing both sides of the sheet, the wrinkle phenomenon of one image does not occur, and a copy with good image quality can be obtained.

Furthermore, the sheet conveying means does not need to maintain a strong pressure contact with the sheet pressing roller.

For example, by reducing the wall thickness, the heat capacity can be set low, thereby shortening the temperature-related start-up time.

Further, due to the structure of the surface of the sheet pressing roller, almost no toner particles are transferred to the surface of the sheet pressing roller, thereby making it possible to improve image quality.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing one embodiment of the present invention, and FIG. 2 is a schematic diagram showing an embodiment of the present invention.
FIG. 2 is an enlarged view showing main parts of the embodiment shown in the figure. Figure 3 is a diagram showing the operation of an embodiment of the present invention, Figure 4.5.
The figure is a schematic diagram showing another embodiment of the invention. ]... Fixing section, 3... Sheet pressing roller, 4...
Heating roller for sheet conveyance, 4A, 15... Halogen lamp, 10... Belt for sheet conveyance, 16... Reflective shade. Figure 1 Figure 2 Drawing identification 1 Large - 50x50 -, Hl ↑♀ Hornworm face (〃ml)

Claims (1)

[Scope of Claims] ] is disposed on the unfixed image bearing surface side of the sheet on the conveyance path of the sheet bearing the unfixed image, and is rotated in accordance with the conveyance direction of the sheet; at least one sheet presser roller having a plurality of interspersed protrusions each having a surface area of 50 x 50 μm or less, and the sheet presser disposed at a position facing the sheet presser roller; It has a surface that has a larger contact area with the sheet than the roller, and moves in the same direction as the sheet feeding direction at the portion corresponding to the sheet presser roller, and comes into contact with the back side of the unfixed image bearing surface of the sheet and presses the sheet. and a sheet conveying means for heating the sheet. A fixing device for a wet-type electronic copying machine, comprising a heating member for heating the sheet conveying means. 2. A fixing device for a wet-type electronic copying machine as set forth in claim 1, wherein the sheet conveying means is constituted by a hollow roller having one circumferential surface smoothed. 3. The fixing device for a wet-type electronic copying machine according to claim 1, wherein the sheet conveying means is constituted by a belt that can be tightly attached to the circumferential surface of the presser roller while surrounding a part of the circumferential surface of the presser roller.