JPH05333736A - Fixing device for electrophotograhic device - Google Patents

Abstract

PURPOSE:To prevent the occurrence of permanent distortion of a fixing roller and to prevent the deterioration of copying quality and the shortening of the life of the fixing roller. CONSTITUTION:The device is provided with three upper, intermediate and lower heat rollers 201, 202 and 203, and an upper fixing part is formed between the upper and intermediate heat rollers 201 and 202, and a lower fixing part is formed between the intermediate and lower heat rollers 202 and 203. When black and white copying is performed, the intermediate heat roller 202 which can contact with and separate from the upper and lower heat rollers 201 and 203 is arranged on the lower fixing part where the roller 202 is separated from the upper heat roller 201 and press-contacted with the lower heat roller 203, and when full-color copying is performed, the intermediate heat roller 202 is arranged on the upper fixing part where the roller 202 is separated from the lower heat roller 203 and press-contacted with the upper heat roller 201, and when the copying device is stopped, or in a standby state, the roller 202 is arranged on the lower fixing part where the permanent distortion of the roller surface generated by the press-contact state is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a fixing device having three fixing rollers, first to third fixing rollers, and a pressure contact portion between the first and second fixing rollers and a pressure contact portion between the second and third fixing rollers. The present invention relates to an electrophotographic apparatus in which a fixing unit is formed on each of the above.

[0002]

2. Description of the Related Art For example, in full-color copying in a full-color copying machine, a yellow image is formed by exposing a photosensitive member to form an electrostatic latent image corresponding to an original image and developing the electrostatic latent image with toner. ,
Toner images of three colors, magenta and cyan, are formed, and these toner images are transferred onto a sheet in a superposed state. Then, the three-layer toner image on the sheet is heated between two heat rollers of the fixing device to be melted and fixed on the sheet to obtain a full-color image.

As described above, in full-color copying, it is necessary to fix the three-layer color toner images on the paper between the two heat rollers without causing separation between the color toner images. Therefore, the color toner of each color used for full-color copying has different physical properties from the black toner used for black-and-white copying, and has low releasability. Therefore, as a heat roller for full-color copying, the surface is very smooth,
A material having a high releasability for toner is used.

However, the heat roller as described above is expensive and has low durability,
In a copying machine capable of full-color copying and black-and-white copying, the copying cost of black-and-white copying is high. Although this problem can be addressed by providing separate fixing devices for full-color copying and black-and-white copying, if two independent fixing devices are provided, the mechanism becomes complicated and the device becomes large. become.

On the other hand, Japanese Laid-Open Patent Publication No. 51-98036 has three upper, middle and lower heat rollers to form a first fixing portion between the upper and middle heat rollers and to form the middle and lower heat rollers. A fixing device that forms a second fixing portion between heat rollers is disclosed.

Therefore, it is conceivable to use this structure, for example, to use the above-mentioned first fixing unit as a fixing unit for full-color copying and the second fixing unit as a fixing unit for black-and-white copying. With such a configuration, as in the case of the above-described method in which two fixing devices are provided, the best fixing operation can be performed by the optimum heat roller in each of full-color copying and monochrome copying. Further, as compared with the case where separate fixing devices for full-color copying and black-and-white copying are provided, it is easy to design a paper transport mechanism to the fixing device,
The structure can be simplified, the cost can be reduced, and the device can be downsized.

However, in the above fixing device,
Since the three middle and lower heat rollers are constantly in pressure contact, the lower heat roller rotates even when the first fixing unit is used, while the upper heat roller rotates even when the second fixing unit is used. To do. Further, the upper, middle and lower heat rollers rotate in different directions when the first fixing section is used and when the second fixing section is used, and rotate in the forward and reverse directions.
Therefore, in the structure of the fixing roller outer peripheral arrangement member such as a thermistor for temperature detection, a cleaning roller, and a peeling claw for preventing sheet entrainment, which are pressed against each heat roller,
Special consideration is required to prevent vibration and wear and to make proper sliding contact with the outer peripheral surface of the heat roller. Also, sliding contact with the fixing roller outer peripheral member,
Further, due to the sliding contact between the heat rollers, the wear of the heat rollers is likely to progress, which shortens the life of the heat rollers and increases the running cost.

Therefore, as shown in FIGS. 4 and 5 which are explanatory views of the present invention, the applicant of the present invention, for example, sets the middle heat roller 202 to the upper heat roller 201 and the lower heat roller 2.
When the first fixing section, that is, the upper fixing section is used, the medium heat roller 202
Is separated from the lower heat roller 203 and the upper heat roller 2
01, and when the second fixing section, that is, the lower fixing section is used, the middle heat roller 202 is connected to the upper heat roller 2
01 has been previously proposed (Japanese Patent Application No. 4-51762).
issue). According to such a configuration, only the heat roller used is rotated and the rotation directions other than those of the medium heat roller can be made constant, so that the above points can be improved.

[0009]

However, in the case where the surface layer portion of the heat roller is formed of, for example, a rubber material, for example, the middle heat roller has the upper or lower heat rollers 201 and 203 even when the fixing device is not used. In a configuration in which one of them is constantly in pressure contact, if this pressure contact state lasts for a long time, permanent deformation may occur in the rubber material depending on the combination with the heat roller to which the middle heat roller 202 is pressure contacted and deform. become. In this case, an offset in which toner adheres to the surface of the heat roller, defective fixing of the toner image, and the like occur, resulting in a marked decrease in copy quality and a shortened life of the heat roller.

[0010]

In order to solve the above-mentioned problems, a fixing device for an electrophotographic apparatus according to the present invention has three fixing rollers, that is, first to third fixing rollers, for example, upper, middle and lower heat rollers. And a first fixing portion is formed in a pressure contact portion between the first fixing roller and the second fixing roller, and a second fixing roller and a third fixing roller are formed.
In a fixing device of an electrophotographic apparatus in which a second fixing portion is formed in a pressure contact portion with a fixing roller, the above-mentioned first and second fixing portions are formed together with other fixing rollers among the first to third fixing rollers. A separating / contacting fixing roller is provided so as to be capable of moving in and out of contact with another fixing roller, and a position where the separating / contacting fixing roller is brought into pressure contact with another fixing roller to form a first fixing portion and a second fixing portion A separating / contacting drive unit that drives the fixing roller to a position where it is pressed against another fixing roller to be formed, and at the same time, separates the remaining fixing rollers other than the above-mentioned fixing rollers that are in a pressed contact state from the second fixing roller. When the fixing operation is performed by the first fixing section, the separating / contacting fixing roller is brought into pressure contact with another fixing roller which should form the first fixing section, and when the fixing operation is performed by the second fixing section, 2 Form the fixing section When the fixing operation is not performed due to the pressure contact with another fixing roller, the contact / disengagement is performed so that the permanent deformation of the roller surface caused by the pressure contact with the separating / fixing roller is the combination of the smaller ones. And a control means for controlling the driving means.

[0011]

According to the above structure, the separating and fixing roller is the first fixing roller.
When the fixing unit performs the fixing operation, it is pressed against another fixing roller which should form the first fixing unit, and when the second fixing unit performs the fixing operation, the other fixing roller which should form the second fixing unit. Is pressed against. When the fixing operation is not performed, that is, when the power switch is turned on and the image forming operation is not performed, and when the power switch is stopped, the pressure contact state with the separation / contact fixing roller is performed. The permanent deformation of the roller surface caused by the above is pressed against the fixing roller having the smaller combination. As a result, the occurrence of permanent distortion due to the pressure-contact operation of the fixing roller is suppressed, so that the copy quality is deteriorated due to the offset of the toner adhering to the surface of the fixing roller and the defective fixing of the toner image, and the short life of the fixing roller. Is suppressed.

[0012]

【Example】

[Embodiment 1] An embodiment of the present invention will be described below with reference to FIGS. As shown in FIG. 2, a full-color copying machine (hereinafter, simply referred to as a copying machine) as an electrophotographic apparatus according to the present embodiment has an original placing table 3 made of hard transparent glass on the upper surface thereof, and the original placing table 3 is used. An exposure optical system section 4 is provided below the table 3. This exposure optical system unit 4
A lamp unit 5 for scanning an original document (not shown) placed on the original document table 3 while irradiating light, a plurality of reflecting mirrors 6 for guiding the reflected light from the original document to the photoconductor 8, and The lens unit 7 is arranged in the optical path of the reflected light.

A charging charger 9 for charging the surface of the photoconductor 8 to a predetermined potential is provided on the outer periphery of the photoconductor 8. Further, an interimage eraser (from the charger 9 in the rotating direction of the photoconductor 8) is provided. (Not shown), black developing tank 1
0, yellow developing tank 11, magenta developing tank 12, cyan developing tank 13, intermediate transfer device 14, cleaning device 15
And the static eliminator 16 is arranged in this order.

The intermediate transfer device 14 is the transfer belt 1
7. Rollers 18, 19 supporting this transfer belt 17
20, the transfer belt 17 is pressed against the photoconductor 8
The first transfer roller 21 that transfers the toner image formed on the surface to the transfer belt 17, and is pressed against the roller 20 via the transfer belt 17 at the time of transferring the toner image onto the paper, and the toner image on the surface of the transfer belt 17 is transferred onto the paper. The second transfer roller 22 for transferring the toner to the surface and the cleaning device 23 for removing the residual toner on the surface of the transfer belt 17 are provided.

A registration roller 24, a paper feed cassette 25 and a paper feed tray 26 for feeding the paper to the intermediate transfer device 14 at a predetermined timing are provided on the paper feed side of the intermediate transfer device 14 and these paper feed cassettes are provided. In the vicinity of the sheet feeding tray 25 and the sheet feeding tray 26, sheet feeding rollers 27, 27 and a conveying roller 28 are provided. Intermediate transfer device 14
A suction unit 100 that conveys a sheet, a fixing device 200, a sheet discharge roller 30, and a sheet discharge tray 31 are provided in the sheet discharge direction.

The suction unit 100 is provided with a conveyor belt (not shown), and the conveyor belt is driven by a belt drive motor (not shown) to move around,
The sheet on which the unfixed toner image is transferred is conveyed to the fixing device 200 while being attracted to the belt.
Further, the suction unit 100 is driven by, for example, a cam mechanism having the above belt drive motor as a drive source,
It is adapted to rotate between an upper position and a lower position. The above-mentioned upper position is a position where a sheet can be conveyed to an upper fixing portion of the fixing device 200 described later, and the lower position is
It is a position where the sheet can be conveyed to the lower fixing unit.

As shown in FIG. 3, the fixing device 200 has an upper heat roller 201 as a first fixing roller, a middle heat roller 202 as a second fixing roller and a separating / contacting fixing roller, and a third fixing roller. Lower heat roller 20
3 and 3 are provided in parallel in the vertical direction. In this embodiment, the upper heat roller 201 and the middle heat roller 2
The upper fixing portion, which is a first fixing portion formed with the pressure contact portion with 02, performs fixing during full-color copying, while the second fixing portion is formed with the pressure contact portion between the middle heat roller 202 and the lower heat roller 203. The lower fixing unit as a unit performs fixing at the time of black-and-white copying.
Therefore, the upper heat roller 201 is provided with a silicon rubber layer having a high releasability and having a thickness of 2 mm, and the middle heat roller 202 is provided with a thickness of 20 mm around the core metal.
The lower heat roller 203 having a Teflon coating of μm is provided with a silicon rubber layer having a thickness of 4 mm around the core metal.

The difference in thickness of the silicon rubber layer between the upper heat roller 201 and the lower heat roller 203 is caused by the difference in control temperature between the two heat rollers 201 and 203. That is, the thicker the rubber layer is, the larger the difference between the temperature of the surface of the rubber layer and the temperature of the boundary surface between the core metal and the rubber layer becomes. The larger this temperature difference is, the adhesion between the core metal and the rubber layer becomes larger. The strength becomes weak. When the temperature of the interface between the cored bar and the rubber layer is 230 ° C. or higher, the adhesive strength between the cored bar and the rubber layer is significantly reduced, and the rubber layer is peeled off from the cored bar. The surface temperature of the upper heat roller 201 needs to be 190 ° C., while that of the lower heat roller 203 is 130 ° C., so that the rubber layer of the lower heat roller 203 can be thickened.

Each of the heat rollers 201 to 203 is hollow, and the heater lamp 20 for heating is provided in the hollow portion.
4 are provided respectively. The upper heat roller 20
1, a heater lamp 204 of 650 w, a middle heat roller 202 of 350 w and 300 w, and a lower heat roller 203 of 350 w are provided. Around the upper or lower heat rollers 201 to 203, a thermistor 205 for detecting the surface temperature thereof, a thermostat (not shown) for preventing overheating incorporated in a circuit of the heater lamp 204, and surfaces of the heat rollers 201 to 203. A cleaning roller 206 for removing the toner and the like adhering to the is provided. Further, around the middle and lower heat rollers 202 and 203, a peeling claw 207 for peeling the paper from the roller surface is formed.
On the other hand, an oil application roller 208 is provided around the upper heat roller 201. The oil applying roller 208 has a structure in which fibers are wound around a tank containing silicon oil, and the fibers are impregnated with silicon oil through small holes formed in the tank.
Then, the upper heat roller 2 is moved by the oil applying roller 208.
By applying silicone oil to the surface of No. 01, the color toner image is prevented from adhering to the roller surface, that is, offset is ensured, and the releasability of the color toner image is secured, and gloss is imparted to the full-color copy image. ing.

In order to form the upper fixing portion and the lower fixing portion, in this embodiment, the middle heat roller 202 is moved up and down to move the middle heat roller 202 relative to the upper and lower heat rollers 201 and 203. Uses a mechanism to separate and connect. Next, the heat roller separating / contacting mechanism will be described with reference to FIGS.

Upper, middle and lower heat rollers 201, 20
2. 203 are heat rollers 201 to 20 respectively
Upper, middle and lower holders 209 provided at both ends of
It is rotatably held by bearings (not shown) by 210 and 211. These upper or lower holders 209-
The cleaning roller 20 includes the cleaning rollers 20.
6 is rotatably attached to the corresponding heat rollers 201 to 203 in a state of always being in contact therewith. Each holder 2
09-211, the end on the paper output side is the connecting shaft 21 respectively.
A roller support base 213 is swingably connected to the roller support base 213. On the other hand, the ends of the upper and lower holders 209 and 211 on the sheet entering side are pulled downward and upward by a tension spring 214, respectively. Engagement portions 209a and 211a are formed at the paper-insertion-side ends of the upper and lower holders 209 and 211, while the roller support base 213 is engaged with the above-described engagement portion 209a and is moved downward. An engaging portion 213a that restricts the rotation of the upper holder 209 and an engaging portion 213b that engages with the engaging portion 211a and restricts the rotation of the lower holder 211 upward are formed.

The oil application roller 208 is the roller holder 2
It is rotatably held at one end of 15. The roller holder 215 is swingably connected to the roller support base 213 near the center by a connecting shaft 215a. A compression spring 216 and an eccentric cam 2 are provided at the other end of the roller holder 215.
And 17 are provided. The compression spring 216 urges the roller holder 215 to rotate in a direction in which the oil application roller 208 is separated from the upper heat roller 201. On the other hand, the eccentric cam 217 is rotated by being driven by the oil application roller cam drive mechanism 254 shown in FIG. 11, so that the roller holder 2 is resisted against the biasing force of the compression spring 216.
15 is rotated so that the oil applying roller 208 is brought into pressure contact with the upper heat roller 201.

An opening-shaped cam arranging portion 210a is formed at the end of the middle holder 210 on the paper input side.
An eccentric cam 219 formed on the cam shaft 218 is arranged at 0a. The cam shaft 218 is supported by a support member (not shown) so as to rotate at a fixed position. The eccentric cam 219 and the upper edge portion 210 of the cam disposing portion 210a.
An interposition plate 220 is provided between the interposition plate 22 and b.
In No. 0, the paper output side end is swingably connected to the roller support base 213 by a connecting shaft 221. A screw 222 is screwed to the sheet insertion side end of the interposition plate 220 so as to pass through the upper edge 210b of the cam arrangement portion 210a. This screw 222
The compression spring 22 is provided between the head of the head and the upper edge 210b.
Three are arranged. Therefore, the rotation of the cam shaft 218, that is, the eccentric cam 219 moves the middle holder 210, that is, the middle heat roller 202 in the vertical direction, and makes contact with the upper and lower heat rollers 201 and 203. In this case, the sliding contact state between the eccentric cam 219 and the middle holder 210 can be adjusted by rotating the screw 222. Also, the upper and lower heat rollers 201.
The separation / contact state of the middle heat roller 202 with respect to 203 is determined by the separation / contact sensor 224.2 provided on the roller support base 213.
It is detected at 25.

Above and below heat rollers 201 to 2
In the rotation of No. 03, the middle heat roller 202 is driven and the upper and lower heat rollers 201 and 203 are driven, and the middle heat roller 202 and the cam shaft 218 are the same as those in FIG.
The heat roller drive mechanism 245 and the cam drive mechanism 246 shown in FIG. The cam drive mechanism 246, the middle holder 210,
The eccentric cam 219 and the heat roller drive motor 253 shown in FIG.

The heat roller driving mechanism 245 has the input shaft 2 to which the driving force is transmitted from the heat roller driving motor 253.
31 has an input gear 232, and between the input gear 232 and the gear 238 provided on the middle heat roller 202,
It has gears 233 to 237. Gears 234 to 236
As shown in FIGS. 7 and 8, is rotatably supported by a gear support plate 239 that rotates about the gear 233, and the gears 234 and 235 are constantly meshed with the gear 233. The operation projection 23 is provided on the gear support plate 239.
9a is formed, and the rod portion 240a of the solenoid 240 is connected to the operation protrusion 239a.

When the middle heat roller 202 is pressed against the lower heat roller 203 as shown in FIG. 4, the solenoid 240 has a rod portion 240a as shown in FIG.
Are controlled to advance. In this case, the gear support plate 2
39 rotates clockwise, and the gear 234 shifts to the gear 23.
7 and the gear 236 separates from the gear 237. Therefore, the rotation of the input gear 232 in the clockwise direction is transmitted to the middle heat roller 202 via the gears 233, 234, 237, and 238, and the middle heat roller 202 rotates in the clockwise direction and the lower heat roller 203 moves. The paper rotates between the heat rollers 202 and 203 in the counterclockwise direction, and is fed toward the paper discharge roller 30. In addition, the solenoid 240, as shown in FIG.
When 2 is pressed against the upper heat roller 201, the rod portion 240a is controlled to retract as shown in FIG. In this case, the gear support plate 239 rotates counterclockwise, the gear 236 meshes with the gear 237, and the gear 23
4 separates from gear 237. Therefore, rotation of the input gear 232 in the clockwise direction causes the gears 233, 235, 236 to rotate.
Transmitted to the middle heat roller 202 via 237 and 238, the middle heat roller 202 rotates in the counterclockwise direction and the upper heat roller 201 rotates in the clockwise direction. It is delivered in the direction of the discharge roller 30.

Further, in the cam drive mechanism 246, as shown in FIG. 6, the input gear 232 meshes with the gear 241, and this gear 241 meshes with the input gear 242c of the spring clutch 242 provided on the cam shaft 218. There is. The spring clutch 242 is shown in FIGS.
As shown in Fig. 1, set the two locking protrusions 242a and 242b into one.
It is located at 80 ° and has these locking protrusions 242a.2.
The operating portion 243a of the solenoid 243 can be engaged and disengaged with respect to 42b. Then, for example, the above-mentioned operating portion 24
As shown in FIG. 9, when 3a engages with the locking projection 242b, the maximum eccentric portion of the eccentric cam 219 drives the middle holder 210 downward, so that the middle heat roller 202 is pressed against the lower heat roller 203. When the operating portion 243a engages with the locking projection 242a as shown in FIG. 10 while moving to the lower fixing portion position, the middle holder 210 is driven upward by the maximum eccentric portion of the eccentric cam 219. Then, the middle heat roller 202 is moved to the position of the upper fixing portion where it is pressed against the upper heat roller 201. The engagement / disengagement operation of the operating portion 243a of the solenoid 243 with respect to the locking projections 242a and 242b of the spring clutch 242 is as follows.
The engagement operation is performed by turning off the solenoid 243, and the releasing operation is performed by turning on the solenoid 243.
The pressure contact force of the middle heat roller 202 with respect to the upper and lower heat rollers 201 and 203 can be changed by replacing the tension spring 214 shown in FIG. 4 or changing the stop position of the eccentric cam 219.

The copying machine, as shown in FIG.
A control device 251 is provided as control means including a microcomputer for controlling the suction unit 100 and the fixing device 200. This control device 251 is based on the separation / contact sensors 224 and 225 and other input keys and the like, as described later, and as described later, the heat roller drive motor 253 and the solenoid 24.
0.243, the heater lamp 204, the oil application roller cam drive mechanism 254, and the like are controlled in operation.

That is, for example, when full-color copying is performed, the middle heat roller 202 is the lower heat roller 2
03 is separated from the upper heat roller 201 by pressure contact with the upper heat roller 201, and the middle heat roller 202 is separated from the upper heat roller 201 by pressure contact with the lower heat roller 203. When the standby state is not performed and the power switch is stopped in the OFF state, the middle heat roller 202 is separated from the upper heat roller 201 and press-contacted to the lower heat roller 203 as in the case of performing black-and-white copying. It has become.

Here, the separation / contact control as described above is performed on the heat rollers 201 to 203 during the stand-by and stop of the copying machine for the following reason. During the fixing operation in full-color copying, not only the temperature but also the width of the fixing portion, that is, the nip width is sufficiently required. Since the rubber layer of the upper heat roller 201 is thin as described above, this nip width is ensured by increasing the pressure contact force between the upper heat roller 201 and the middle heat roller 202. The pressure contact force between the upper and middle heat rollers 201 and 202 and the pressure contact force between the middle and lower heat rollers 202 and 203 are determined by the tension springs 214 and 214, respectively. Reference numeral 214 denotes the tension spring 21 on the lower heat roller 203 side.
The pulling force is stronger than 4. Therefore, considering the permanent distortion of the rubber layers of the upper and lower heat rollers 201 and 203, the home position of the middle heat roller 202 when the fixing device 200 is not used is such that the pressure contact force between the heat rollers is small, and It is preferable to set the position where it is pressed against the roller 203, that is, the position of the lower fixing unit, and is controlled in this way when the copying machine is on standby and when it is stopped.

In the above arrangement, first, the full-color copy operation in this copying machine will be described. First, as shown in FIG. 2, the surface of the photoconductor 8 rotating in the B direction is uniformly charged by the charging charger 9, and the exposure optical system unit 4
Thus, the first scanning of the document on the document table 3 is performed. Light reflected from the original is exposed on the surface of the photoconductor 8 between the charger 9 and the inter-image eraser (not shown) through a blue color separation filter (not shown) and a slit (not shown). The point is illuminated and the photoconductor 8
Is exposed to form an electrostatic latent image. Next, the potential of the non-image area on the photoconductor 8 is removed by the inter-image eraser, and then the electrostatic latent image is developed by the yellow developing tank 11 to form a yellow toner image.

Next, the yellow toner image on the surface of the photoconductor 8 is transferred onto the transfer belt 17 which moves in the direction C by the first transfer roller 21 to which a negative high voltage is applied. The residual toner on the surface of the photoconductor 8 is removed by the cleaning device 15, and the residual potential on the surface of the photoconductor 8 is removed by the static eliminator 16.

When the series of operations described above is completed, the photoconductor 8 is charged again by the charger 9, and the exposure optical system unit 4 scans the document for the second time. In this case, a green color separation filter is used, and the electrostatic latent image formed on the photoconductor 8 is developed by the magenta toner in the magenta developing tank 12. The magenta toner image on the surface of the photoconductor 8 thus formed is transferred by the first transfer roller 21 so as to be superimposed on the previous yellow toner image on the transfer belt 17. Thereafter, in the same manner, a third scanning is performed by the exposure optical system unit 4 using the red color separation filter, and the cyan toner image is formed on the photoconductor 8 by the development with the cyan toner in the cyan developing tank 13. It is formed. This cyan toner image is transferred onto the magenta toner image on the transfer belt 17.

Next, the second transfer roller 22 which has been separated from the transfer belt 17 in the above operation is transferred to the transfer belt 1.
When the sheet is pressed against 7 and a negative voltage higher than the surface potential of the transfer belt 17 is applied to the second transfer roller 22, the sheet is conveyed from the sheet feeding cassette 25 or the sheet feeding tray 26 via the registration roller 24. The three-layer toner image on the transfer belt 17 is transferred onto the paper.

The sheet on which the toner image is transferred is conveyed to the fixing device 200 by the suction unit 100. At this time, since the suction unit 100 is held at the upper position, the sheet is conveyed to the upper fixing section between the upper and middle heat rollers 201 and 202. In the upper fixing unit, the three-layer color toner images on the paper are heated and melted by the upper and middle heat rollers 201 and 202 and fixed on the paper. At this time, the upper heat roller 2
Since 01 is supplied with silicone oil from the oil application roller 208, offset of the toner image on the upper heat roller 201 is prevented, and gloss is imparted to the full-color toner image on the paper.

The paper discharged from the fixing device 200 is discharged onto the discharge tray 31 by the discharge rollers 30.

Next, the black-and-white copying operation of this copying machine will be described. First, the surface of the photoconductor 8 is uniformly charged by the charging charger 9, and the exposure optical system unit 4 scans the document on the document mounting table 3. The reflected light from the original does not pass through the color separation filter and slit,
It is guided to the exposure optical system unit 4 and is irradiated onto the photoconductor 8 to form an electrostatic latent image on the photoconductor 8. After that, the electrostatic latent image is developed by the black developing tank 10, and the black toner image formed by this is transferred to the transfer belt 17 and further transferred to a sheet.

The above-mentioned paper on which the toner image has been transferred is subjected to the middle and lower heat rollers 2 by the suction unit 100.
The toner image is conveyed to the lower fixing unit between 02 and 203, and the toner image is fixed on the sheet. The sheet discharged from the fixing device 200 is discharged onto the discharge tray 31 by the discharge roller 30.

Next, the fixing device 200 at the time of stand-by and stop of the copying machine, at the time of full color copying and at the time of black and white copying.
The operation will be described with reference to the flowchart of FIG. When the copying machine is in the stopped state in which the power switch (not shown) is OFF and in the standby state in which the power switch is ON (S1), the middle heat roller 202 is It is held at the position of the lower fixing unit that is in pressure contact with the lower heat roller 203 (S2). Therefore, the fixing device 20
In the 0 heat roller driving mechanism 245, as shown in FIG. 7, the rod portion 240a of the solenoid 240 has advanced, the gear 234 meshes with the gear 237, and the gear 236 is separated from the gear 237. In the cam drive mechanism 246, as shown in FIG. 9, the operating portion 243a has the locking projection 2
42b is engaged. In addition, the suction unit 10
Zero is placed in the lower position.

Next, after the power switch is turned on after the copying machine is stopped and the copy start button is turned on, or when the copy start button is turned on from the standby state, the black and white copy selection key When the black-and-white copy is selected by the ON operation (S4), the output of the separation / contact sensors 224 and 225 causes the middle heat roller 2
When it is confirmed that 02 is at the lower fixing unit position (S5),
Black-and-white copying is performed (S7). On the other hand, in S5,
When the middle heat roller 202 is at the upper fixing unit position,
After turning on the solenoid 243, turn it off (S
6) After rotating the eccentric cam 219 by 180 ° and moving the middle heat roller 202 to the position of the lower fixing unit, black and white copying is performed.

Next, after the black-and-white copy is completed (S8), when the predetermined time counted by the timer has not elapsed (S9), for example, when the black-and-white copy is restarted by the ON operation of the copy start button, (S10),
Go to S7. On the other hand, when the predetermined time has not elapsed (S9) and the full-color copy is started by the ON operation of the full-color copy selection key and the copy start button (S10), S1 to be described later
Go to 4.

Further, in S9, another black-and-white copy,
Alternatively, when a predetermined time elapses without starting the full-color copying, the process directly shifts to a standby state or a stopped state by turning off the power switch (S11).

On the other hand, when the full-color copy is selected by the ON operation of the full-color copy selection key in S4, the solenoid 243 is turned on and then turned off to rotate the eccentric cam 219 by 180 °, and the middle heat roller 202 is turned on. It is moved to the upper fixing unit position (S12).

As a result, in the cam drive mechanism 246, from the state shown in FIG. 9, the operating portion 2 of the solenoid 243 is engaged with the locking projection 242b of the spring clutch 242.
43a is disengaged, and the locking projections 242a and 242b are released.
After rotating by 180 °, as shown in FIG. 10, the operating portion 243a is engaged with the locking projection 242a. With this rotation, the eccentric cam 219 rotates 180 °, and as shown in FIG. 5, the maximum eccentric portion of the eccentric cam 219 causes the middle holder 2 to move.
10 is driven upward, and the middle heat roller 202 is pressed against the upper heat roller 201. Further, the eccentric cam 217
The oil applying roller 208 is brought into pressure contact with the upper heat roller 201 by being driven.

In the above state, the upper holder 20
Since 9 is pushed by the middle heat roller 202 and rotates slightly counterclockwise, the upper heat roller 201 is held at a position moved slightly higher than when it is separated from the middle heat roller 202. On the other hand, the rotation of the lower holder 211 in the counterclockwise direction by the tension spring 214 is restricted by the engagement portion 211a thereof engaging with the locking portion 213b, so that the lower heat roller 203 is connected to the middle heat healer 202. It is kept in a separated state.

Further, in the heat roller drive mechanism 245, as shown in FIG. 8, the rod portion 240a of the solenoid 240 retracts, the gear 236 meshes with the gear 237, and the gear 234 separates from the gear 237. Therefore, the rotation of the input gear 232 in the clockwise direction rotates the middle heat roller 202 in the counterclockwise direction and the upper heat roller 201 in the clockwise direction. Further, the suction unit 100 is held at the upper position.

After that, when it is confirmed that the middle heat roller 202 is at the upper fixing portion position (S13), full color copying is performed (S14). On the other hand, in S13, when the middle heat roller 202 is at the lower fixing unit position, S
The process returns to step 12 and the operation is performed again.

Next, after the completion of full-color copying (S1
5) If the predetermined time has not elapsed (S16),
The process proceeds to S10.

In S16, if a predetermined time elapses without starting another full-color copy or black-and-white copy, the solenoid 243 is turned ON and then OF is turned off.
After setting to F (S17), the eccentric cam 219 is rotated 180 °, the middle heat roller 202 is moved to the lower fixing portion position (S18), and then the process proceeds to S11.

When the above-described operation of S17 is performed, in the cam drive mechanism 246, the engagement portion 243a of the solenoid 243 is disengaged from the engagement protrusion 242a of the spring clutch 242 from the state shown in FIG. Then, as shown in FIG. 9, the operating portion 2 is attached to the locking projection 242b.
43a engages. Therefore, as shown in FIG. 4, the middle holder 210 is driven downward by the maximum eccentric portion of the eccentric cam 219, and the middle heat roller 202 is moved to the lower heat roller 203.
Meanwhile, the upper heat roller 201 is separated from the middle heat roller 202. Further, the eccentric cam 217 is
The oil application roller 208 is rotated by 0 ° and pushed by the compression spring 216 to separate the oil application roller 208 from the upper heat roller 201.

Further, in the heat roller drive mechanism 245, as shown in FIG. 7, the rod portion 240a of the solenoid 240 advances and the gear 234 meshes with the gear 237, while the gear 236 separates from the gear 237. Therefore, the rotation of the input gear 232 in the clockwise direction causes the middle heat roller 202 to rotate in the clockwise direction and the lower heat roller 2 to rotate.
03 can be rotated counterclockwise. Further, the suction unit 100 is held at the lower position.

[Embodiment 2] Another embodiment of the present invention will be described below with reference to FIGS. 6 and 12 to 15.
For convenience of explanation, members having the same functions as those of the members shown in the drawings of the above-described embodiments are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 12, in the fixing device 400 of this embodiment, the middle heat roller 2 as the second fixing roller is used.
02 is provided in a fixed state on the roller support base 401, the upper heat roller 201 as a first fixing roller and a separation / contact fixing roller is provided in the upper holder 402, and the third heat roller and a lower heat roller as a separation / contact fixing roller. 203
Are provided on the lower holder 403. Upper heat roller 2
01, a thermistor 205 supported by the upper holder 402, a cleaning roller 206, and an oil application roller 208 are provided, and around the middle heat roller 202, the thermistor 2 supported by a roller support base 401.
05 and a peeling claw (not shown) are provided, and a thermistor 205, a cleaning roller 206, and a peeling claw (not shown) are provided around the lower heat roller 203.

The upper and lower holders 402 and 403 are connected to the roller supporting base 401 by a connecting shaft 404 so that the paper-inserting side portions thereof are swingable, and the output-side ends thereof are downwardly moved by a tension spring 405. Pulled upwards. The tension spring 405 that pulls the lower holder 403 has a larger tension force than the tension spring 405 that pulls the upper holder 402 because the lower heat roller 203 is pressed against the middle heat roller 202 with a large pressure contact force. .. Further, an eccentric cam 406 is arranged at the upper edge portion of the upper holder 402 at the end on the sheet input side.
An eccentric cam 407 is arranged at the lower edge portion of the end portion on the sheet input side. The eccentric cams 406 and 407 are provided such that the maximum eccentric portions thereof are always oriented in the same direction.

During black-and-white copying, the eccentric cams 406 and 407 are at their maximum, as shown in FIG. 13, which shows a simplified structure for driving the upper and lower heat rollers 201 and 203 shown in FIG. The eccentric portion is arranged downward, and the upper heat roller 201 is separated from the middle heat roller 202 by the upper holder 402 being driven by the eccentric cam 406 to rotate in the clockwise direction.
03, the lower holder 403 is pulled by the tension spring 405 and rotates clockwise, so that the middle heat roller 2
It is pressed against 02 to form a lower fixing portion for black and white copying. On the other hand, for full color copying,
As shown in FIG. 14, the eccentric cams 406 and 407 are arranged with their maximum eccentric parts facing upward, and the upper heat roller 201
The upper holder 402 is pulled by the tension spring 405 and is rotated in the counterclockwise direction.
The lower heat roller 203 is separated from the middle heat roller 202 by being pressed against 2 to form an upper fixing portion for full-color copying, and the lower holder 403 being driven by the eccentric cam 407 to rotate counterclockwise. It is like this.

The upper and lower heat rollers 201 to 203 are rotated by the middle heat roller 202, as in the fixing device 200 shown in the first embodiment.
1.203 is driven. Medium heat roller 202
Is driven to rotate by a heat roller drive mechanism 245 shown in FIG. 6, and the eccentric cams 406 and 407 are driven to rotate by a cam drive mechanism 246 shown in FIG. In this case, the cam drive mechanisms 246 are individually provided corresponding to the eccentric cams 406 and 407, or one of the eccentric cams 406 and 407 is driven by the cam drive mechanism 246, and the rotation thereof is transmitted to the other by the gear mechanism. Will be configured. Then, in this embodiment, the upper holder 40
2, the tension spring 405, the eccentric cam 406, the cam drive mechanism 246 and the heat roller drive motor 253, and the lower holder 403, the tension spring 405, the eccentric cam 407, the cam drive mechanism 246 and the heat roller drive motor 253, separate and contact each other. Driving means is configured.

The upper and lower cleaning rollers 206,
206 is rotatably held at one end of the roller holders 408 and 408. Each roller holder 408 is a support shaft 40.
It is swingably supported on the upper holder 402 and the lower holder 403 by 8a. In addition, the roller holder 408
Is applied to each cleaning roller 2 by the tension spring 409.
06 is pulled so as to come into pressure contact with the upper or lower heat roller 201/203, while the eccentric cam 410 or 4 is pulled.
11, the cleaning rollers 206 are driven so as to be separated from the upper or lower heat rollers 201 and 203.

Similarly, the oil applying roller 208 is rotatably held at one end of a roller holder 412 rotatably provided on the upper holder 402 by a support shaft 412a.
The roller holder 412 is pulled by a tension spring 413 so that the oil application roller 208 is brought into pressure contact with the upper heat roller 201, while the eccentric cam 414 is driven so that the oil application roller 208 is separated from the upper heat roller 201. It has become so. The eccentric cams 410 and 411 and the eccentric cam 414 are respectively shown in FIG.
Are driven by a cleaning roller cam drive mechanism 415 and an oil application roller cam drive mechanism 416 shown in FIG. 4, and these drive mechanisms are controlled by a control device 417 as a control means shown in FIG. There is. The other configuration is the fixing device 200 shown in the first embodiment.
Is the same as

In the above structure, the power switch is ON
In the standby state, the eccentric cams 406 and 407 are driven by the cam drive mechanism 246, and the maximum eccentric portion is arranged to face downward as shown in FIGS. To be done. Therefore, the lower heat roller 2
03 is pressed against the middle heat roller 202 to form a lower fixing portion for black and white copying, while the upper heat roller 201 is separated from the middle heat roller 202. Further, the cleaning roller 206 and the oil applying roller 208 on the outer circumference of the upper heat roller 201 are driven by the eccentric cams 410 and 414 to be separated from the upper heat roller 201, while the cleaning roller 206 on the outer circumference of the lower heat roller 203 moves the tension spring 409. Is pressed against the lower heat roller 203.
Further, the suction unit 100 is arranged at the lower position.

Next, when the copy start button is turned on after the full-color copy selection key is turned on in the above standby state, the eccentric cams 406 and 407 are set to the positions shown in FIG.
As shown in, the maximum eccentric portion rotates so as to face upward. Therefore, the upper heat roller 201 is the middle heat roller 2
02 is pressed to form an upper fixing portion for color copying, while the lower heat roller 203 is connected to the middle heat roller 202.
And away. Further, the cleaning roller 206 and the oil applying roller 208 on the outer periphery of the upper heat roller 201 are
The upper heat roller 201 is provided by the tension springs 409 and 413.
Meanwhile, the cleaning roller 206 on the outer periphery of the lower heat roller 203 is driven by the eccentric cam 411 and separated from the lower heat roller 203. Further, the suction unit 100 is arranged at the upper position. Then, a full color copy operation is performed. After a lapse of a predetermined time after the completion of the full-color copying operation, the fixing device 400 and the suction unit 100 return to the above-mentioned standby state.

Further, when the copy start button is turned on after the black-and-white copy selection key is turned on from the above-mentioned full-color copy-enabled state, the fixing device 400 and the suction unit 100 shift to the above-mentioned standby state, After that, a black-and-white copy operation is performed.

[Embodiment 3] Still another embodiment of the present invention will be described below with reference to FIGS. 6, 11, and 16 to 18. For convenience of explanation, members having the same functions as those of the members shown in the drawings of the above-described embodiments are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 16, the fixing device 600 of this embodiment is the same as the fixing device 200 of the first embodiment shown in FIG.
One eccentric cam 219 moves the middle heat roller 202 to and from the upper and lower heat rollers 201 and 203, while one eccentric cam 219 moves the upper and lower heat rollers 201 and 203 to the middle position. The heat roller 202 is made to come into contact with and separate from the heat roller 202.

Middle heat roller 2 as second fixing roller
Reference numeral 02 designates a fixed position on the roller support base 601. The upper heat roller 201 as the first fixing roller and the separation / contact fixing roller and the lower heat roller 203 as the third fixing roller and the separation / contact fixing roller are respectively provided. First
The upper holder 602 as a fixing roller supporting member and the lower holder 603 as a third fixing roller supporting member are provided. The upper and lower holders 602 and 603 are swingably connected to the roller supporting base 601 by connecting shafts 604 at the paper input side ends. A cleaning roller 206 and an oil applying roller 208 provided on the outer periphery of the upper heat roller 201, and middle and lower heat rollers 202 and 20.
The cleaning roller 206 provided on the outer periphery of the upper heat roller 201,
It is pressed against the middle heat roller 202 and the lower heat roller 203.

Between the upper edge of the paper output side end of the upper holder 602 and the roller support base 601 and between the lower edge of the paper output side end of the lower holder 603 and the roller support base 601. A compression spring 606 and a compression spring 607 are provided, and the upper holder 60
An eccentric cam 219 is arranged between the lower edge of the sheet ejection side end of No. 2 and the upper edge of the sheet ejection side end of the lower holder 603.
The compression spring 607 that urges the lower holder 603 presses the lower heat roller 203 against the middle heat roller 202 with a large pressure contact force, so that the one having a larger spring force than the compression spring 606 that urges the upper holder 602 is used. It is used.

During black-and-white copying, the eccentric cam 219 has its maximum eccentric portion as shown in FIG. 17, which shows a simplified structure for driving the upper and lower heat rollers 201 and 203 shown in FIG. The upper heat roller 201 is separated from the middle heat roller 202 by the upper holder 602 being driven by the eccentric cam 219 and rotated in the clockwise direction, and the lower heat roller 203 is arranged in the lower holder. The compression spring 607 pushes the compression spring 607 to rotate it clockwise, so that it is pressed against the middle heat roller 202 to form a lower fixing portion for black and white copying. On the other hand, during full-color copying, as shown in FIG. 18, the eccentric cam 219 is arranged with its maximum eccentric portion facing downward, and the upper heat roller 201 is pushed back by the upper holder 602 by the compression spring 606. By rotating in the clockwise direction, it is pressed against the middle heat roller 202 to form the upper fixing portion for full-color copying, and the lower heat roller 20.
3, the lower holder 603 is driven by the eccentric cam 219 to rotate in the counterclockwise direction, whereby the middle heat roller 2
It is designed to be separated from 02.

The upper and lower heat rollers 201 to 203 are rotated by the middle heat roller 202 as in the fixing device 200 shown in the first embodiment, and the upper and lower heat rollers 20 are rotated.
1.203 is driven. Medium heat roller 202
The eccentric cam 219 corresponds to the heat roller drive mechanism 2 shown in FIG.
45 and the cam drive mechanism 246 are rotationally driven, and the control thereof is performed by a control device 251 as a control means shown in FIG. Then, in this embodiment, the upper holder 602, the compression spring 606 and the eccentric cam 219, the cam drive mechanism 246 and the heat roller drive motor 253, and the lower holder 603, the compression spring 607 and the eccentric cam 219, the cam drive mechanism 246 and the heat. The roller driving motor 253 constitutes separate contact / detachment driving means.

In the above structure, the power switch is ON
In the standby state of the state, the eccentric cam 219 is driven by the cam drive mechanism 246, and the maximum eccentric portion is arranged so as to face upward as shown in FIGS. .. Therefore, the lower heat roller 201 is pressed against the middle heat roller 202 to form a lower fixing portion for black-and-white copying, while the upper heat roller 201 is separated from the middle heat roller 202. In addition, suction unit 1
00 is arranged in the lower position.

Next, in the above standby state, when the copy start button is turned on after the full color copy selection key is turned on, the maximum eccentric portion of the eccentric cam 219 faces downward, as shown in FIG. To rotate. Therefore, while the upper heat roller 201 is pressed against the middle heat roller 202 to form the upper fixing portion for color copying,
The lower heat roller 203 is separated from the middle heat roller 202. Further, the suction unit 100 is arranged at the upper position. After that, a full-color copy operation is performed, and when this operation is completed and a predetermined time elapses, the fixing device 600 and the suction unit 100 return to the standby state.

Further, when the copy start button is turned on after the black-and-white copy selection key is turned on from the above-mentioned full-color copy enabled state, the fixing device 600 and the suction unit 100 shift to the above-mentioned standby state, After that, a black-and-white copy operation is performed.

[0071]

In the fixing device of the electrophotographic apparatus of the present invention, among the first to third fixing rollers, the separating / contacting fixing roller forming the above-mentioned first and second fixing portions together with the other fixing roller is the other. The fixing roller is provided so as to be movable toward and away from the fixing roller, and the separating and fixing roller is pressed against another fixing roller where the first fixing section is to be formed and another fixing roller where the second fixing section is to be formed. And a contact / detachment drive means for separating the remaining fixing rollers other than the above-mentioned both fixing rollers in the pressure contact state from the second fixing roller at the same time, and the contact / contact fixing roller. However, when the fixing operation is performed by the first fixing unit, it is pressed against another fixing roller that should form the first fixing unit, and when the fixing operation is performed by the second fixing unit, the second fixing unit is formed. Pressed against other fixing rollers, When the fixing operation is not performed, a control means for controlling the separation / contact driving means so that the separation / contact driving means is pressed into contact with the fixing roller having a smaller permanent deformation of the roller surface caused by the pressure contact state with the separation / contact fixing roller. It is a configuration provided with.

As a result, the occurrence of permanent distortion due to the pressing operation of the fixing roller is suppressed, the copy quality is deteriorated due to the offset of the toner adhering to the surface of the fixing roller and the defective fixing of the toner image, and the life of the fixing roller is shortened. This has an effect of suppressing shortening of life.

[Brief description of drawings]

FIG. 1 is a flow chart showing an embodiment of the present invention and showing a separating operation of a middle heat roller in a fixing device.

FIG. 2 is an overall configuration diagram of a copying machine including the fixing device.

FIG. 3 is an enlarged view showing a configuration near a fixing device shown in FIG.

FIG. 4 is a schematic front view of the heat roller separating / contacting mechanism provided in the fixing device shown in FIG.

FIG. 5 is a schematic front view showing a partially broken state of the heat roller separating / contacting mechanism at the time of full-color copying.

FIG. 6 is a schematic perspective view showing a heat roller drive mechanism and a cam drive mechanism in the fixing device.

FIG. 7 is a schematic front view showing the operation of the heat roller driving mechanism during black-and-white copying.

FIG. 8 is a schematic front view showing the operation of the heat roller drive mechanism during full color copying.

9 is a schematic front view showing the operation of the cam drive mechanism shown in FIG. 6 during black-and-white copying.

FIG. 10 is a schematic front view showing the operation of the cam drive mechanism during full-color copying.

11 is a block diagram showing a configuration of a main part of a control system included in the fixing device shown in FIG.

FIG. 12 is a schematic front view showing another embodiment of the present invention and showing states of a heat roller separation / contact mechanism of the fixing device during black-and-white copying and during standby.

FIG. 13 is an operation explanatory diagram showing the above fixing device in a simplified manner during black-and-white copying and during standby.

FIG. 14 is an operation explanatory diagram of the fixing device shown in FIG. 13 during full-color copying.

15 is a block diagram showing a configuration of a main part of a control system of a copying machine including the fixing device shown in FIG.

FIG. 16 is a schematic front view showing still another embodiment of the present invention, showing a state of a heat roller separation / contact mechanism of the fixing device during black-and-white copying and during standby.

FIG. 17 is an operation explanatory diagram showing the above fixing device in a simplified manner during black-and-white copying and during standby.

FIG. 18 is an operation explanatory diagram of the fixing device shown in FIG. 17 during full-color copying.

[Explanation of symbols]

200 Fixing device 201 Upper heat roller (first fixing roller, separation / contact fixing roller) 202 Medium heat roller (second fixing roller, separation / contact fixing roller) 203 Lower heat roller (third fixing roller, separation / contact fixing roller) 210 Middle Holder (separation contact drive means) 219 Eccentric cam (separation contact drive means) 246 Cam drive mechanism (separation contact drive means) 251 Control device (control means) 253 Heat roller drive motor (separation contact drive means) 400 Fixing device 402 Upper holder (Separation / Detachment drive means) 403 Lower holder (Separation / separation drive means) 405 Extension spring (Separation / separation drive means) 406 Eccentric cam (separation / separation drive means) 407 Eccentric cam (separation / separation drive means) 417 Control device (control means) 600 Fixing device 602 Upper holder (separation contact drive means) 603 Lower holder (separation contact drive means) 606 Compression spring (separation contact drive means) 60 7 Compression spring (separation contact drive means)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiaki Masuda 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation

Claims (1)

[Claims] 1. A first to third fixing roller having three fixing rollers, wherein the first fixing roller and the second fixing roller have a first pressure contact portion.
A fixing device of an electrophotographic apparatus, wherein a fixing portion is formed, and a second fixing portion is formed at a pressure contact portion between a second fixing roller and a third fixing roller, the other fixing roller among the first to third fixing rollers. At the same time, the separation / contact fixing roller forming the first and second fixing portions is provided so as to be movable in and out of contact with another fixing roller, and the separation / contact fixing roller described above is used to form the first fixing portion. It is driven to a position where it is pressed against the fixing roller and a position where it is pressed against another fixing roller on which the second fixing portion is to be formed, and
At this time, the separation / contact driving means for separating the remaining fixing rollers other than the above-mentioned fixing rollers in the pressure contact state from the second fixing roller and the separation / contact fixing roller perform the fixing operation by the first fixing unit. When the fixing operation is performed, the fixing roller is pressed against another fixing roller which should form the first fixing section, and when the fixing operation is performed by the second fixing section, the fixing roller is pressed against another fixing roller which is formed the second fixing section and the fixing operation is performed. When not performed, a control means for controlling the separation / contact driving means is provided so that the separation / contact driving means is pressed against the fixing roller having a smaller permanent deformation of the roller surface caused by the pressure contact state with the separation / contact fixing roller. An electrophotographic device characterized in that