JP2901420B2 - Electrophotographic equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device having three upper, middle, and lower fixing rollers, and a fixing unit for pressing the upper and middle fixing rollers and a pressing unit for the middle and lower fixing rollers. The present invention relates to an electrophotographic apparatus in which is formed.

[0002]

2. Description of the Related Art As a conventional electrophotographic copying machine, as shown in FIG. 5, a fixing device 914 is provided with two upper and lower heat rollers 914a and 914 as fixing rollers.
b is known. This copying machine is capable of black-and-white and full-color copying.
Of the original placed on the original placing table 903 by the light source lamp 902, and the photosensitive member 905 is exposed by the reflected light from the original guided through the filter 904, thereby forming the electrostatic member formed on the photosensitive member 905. The latent image is transferred to the developing device 906
908 or the black toner of the developing device 909, and the toner image is transferred via the intermediate transfer belt 910 onto a sheet supplied from any of the sheet cassettes 911 to 913, and the sheet is fixed. The device 914 is supplied. In the fixing device 914, the upper and lower heat rollers 914a and 914b are pressed against each other, and the toner of the toner image is melted by a fixing unit formed between the heat rollers 914a and 914b, and the toner image is formed. Is fixed on the sheet.

On the other hand, Japanese Patent Application Laid-Open No. Sho 51-98036 discloses that a fixing device is provided with three upper, middle and lower heat rollers, and an upper fixing portion is formed between the upper and middle heat rollers. A lower fixing unit is formed between the upper and lower heat rollers, and a conveying belt for conveying a sheet to the upper and lower fixing units is moved up and down according to the fixing unit to be used. According to such a configuration, by appropriately selecting the material of the upper, middle and lower heat rollers,
The upper and lower fixing sections can support sheets made of various materials such as paper, labels, mylar, and polycarbonate.

[0004]

However, in the latter fixing device having three heat rollers, the former two fixing devices are also required.
Similarly to the fixing device having the heat rollers, in order to support full-color copying and black-and-white copying, both the upper fixing unit and the lower fixing unit can perform the fixing operation at the time of full-color copying and black-and-white copying. If
The following problems occur.

A discharge conveyance path for conveying the paper on which only one-sided copying has been performed from the upper and lower fixing units toward the discharge tray;
In the case of a double-sided copy of a black and white image, an intersecting portion occurs with a re-feeding conveyance path for conveying the sheet on which single-sided copying has been performed to a reversing re-sending device for reversing the sheet and re-supplying the same to the copying machine body. Its structure becomes complicated.

Further, the following problems also occur in the former fixing device. Since it is necessary to perform control in accordance with black-and-white copying and full-color copying in each fixing unit, the control becomes complicated, or it is difficult to perform an optimal fixing operation.

Further, the heat roller for full-color copying is intended to fix a three-layered color toner image on a sheet without adhering to the heat roller surface, that is, without causing offset of the toner image. Are extremely smooth and are expensive and have low durability compared to a heat roller for black and white copying. Therefore, by using heat rollers for full-color copying for the upper and middle heat rollers, both the upper and lower fixing sections can support full-color copying and black-and-white copying, and both fixing sections can be used for full-color copying and black-and-white copying. If used without distinction, the upper and middle heat rollers must be replaced frequently, and the running cost of black and white copying becomes expensive.

Furthermore, the color toner used for full-color copying has a very low softening temperature and a very low viscosity at the time of melting, compared with a black toner for a single color, so that the toner images of the three layers are sufficiently mixed. I have. Therefore, the above-mentioned offset is likely to occur, and in order to surely prevent the offset, a large amount of silicone oil is supplied to the upper and middle heat rollers when the fixing operation at the time of full-color copying is performed in the upper and lower fixing units. For this reason, regardless of whether the fixing operation at the time of the black-and-white copying is performed at the upper fixing unit or the lower fixing unit, the silicone oil used in the fixing operation of the full-color copy adheres to both sides or one side of the sheet. When such a sheet is used for the above-described double-sided copying, the silicone oil adheres to the conveying roller in the re-sending conveyance path, lowers the conveying force, easily causes paper jams, or causes a photoconductor to be damaged. Adherence or intrusion into the developing tank leads to a disadvantage that image quality is deteriorated.

Further, depending on the use of the copy image, there is a demand to copy a black-and-white image on one side and to copy a full-color image on the other side. Therefore, there is a demand for the development of an apparatus that satisfies such a demand and can solve the above-mentioned problem.

[0010]

According to the present invention , there is provided an electrophotographic apparatus comprising:
Alternatively , an electrophotographic apparatus main body for forming a full-color image on a sheet, a reversing and re-feeding apparatus for reversing a sheet ejected from the electrophotographic apparatus main body and supplying the inverted sheet to the electrophotographic apparatus main body again , Resending device
In an electrophotographic apparatus and a control means for controlling, the main body of the electrophotographic apparatus comprises an upper constant <br/> attaching portion of the full-color image formation, a lower fixing portion for monochromatic image formation, the upper fixing portion a discharge conveyance path on for conveying the sheet to the outside, and the lower discharge transport path for transporting the lower fixing portion of the sheet to the outside, the lower
A re-feeding conveyance path for conveying the sheet from the fixing unit to the reversing re-feeding device, and a branch portion between the lower discharge conveyance path and the re-transmission conveyance path.
And the conveyance direction of the sheet discharged from the lower fixing unit.
To switch to the lower discharge conveyance path or retransmission conveyance path
And a gate . Also book
An electrophotographic apparatus according to a second aspect of the present invention has a structure according to the first aspect.
During formation, a single-color image is formed on one side of the sheet, and
/ Full color to form a full color image on the opposite side of
Double-sided image forming operation is possible, and this single color / full color
When the double-sided image forming operation is performed, the control unit
First, a monochrome image is formed on one side of the sheet, and
After that, a full-color image is formed on the opposite side
Then, the above-described electrophotographic apparatus main body and the reversing retransmission device are controlled.
It is characterized by that.

[0011]

According to the above arrangement, the upper fixing section is formed as a fixing section for forming a full-color image, while the lower fixing section is formed as a fixing section for forming a single-color image. The fixing conditions of the image forming section can be individually set for full-color image formation and for a single-color image, that is, for black-and-white image formation. The best fixing operation can be performed in image formation. In addition, since a durable and inexpensive fixing roller can be used for forming the lower fixing portion for forming a black and white image, the frequency of replacing the fixing roller can be reduced, and the running cost in forming a black and white image is reduced. can do. Further, the oil used in the upper fixing roller hardly adheres to the sheet processed in the lower fixing unit, and paper jam and deterioration of image quality due to the oil do not occur. Further, the upper discharge transport path, the lower discharge transport path, and the retransmission transport path do not intersect, and the structure is simple.

In a single-color / full-color double-sided image forming operation, first, a single-color image is formed on one side of the sheet, and then a full-color image is formed on the opposite side. In this case, the sheet on which the toner image of the single-color image has been transferred is subjected to a fixing process in a lower fixing unit of the fixing device, and is then sent to the reversing and re-sending device through the re-sending conveyance path. Then, a toner image of a full-color image is transferred to the reverse surface of the inverted sheet by the main body of the electrophotographic apparatus, and the sheet is subjected to a fixing process in an upper fixing section of a fixing device, and then discharged out of the apparatus. Therefore, during the single-color / full-color double-sided image forming operation, paper jam due to curled paper, paper jam due to oil, and deterioration of image quality do not occur.

That is, a full-color image is formed by fixing a toner layer superimposed on three layers.
After the full-color image is formed, the contraction rate of the front surface, which is the image forming surface, is greater than the contraction ratio of the back surface, and the curl amount is large. On the other hand, since a single-color image, for example, a black-and-white image is formed by fixing only one toner layer, the sheet after forming the black-and-white image has a small curl amount. For this reason, when the paper after the black-and-white copy is sent to the re-sending conveyance path and the reversing re-sending device, when the sheet is properly conveyed, but when the sheet after full-color image formation is sent,
This paper is likely to cause paper jams in the re-sending conveyance path or the reversing re-sending device. Further, when the paper to which the oil after the full-color image is formed is sent to the re-feeding conveyance path and the reversing re-sending device, the above-described oil causes paper jam and deterioration in image quality. Therefore, first, a single-color image is formed on one side of the sheet, and then a full-color image is formed on the opposite side of the sheet. There is no need, and the above problem does not occur.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. A full-color copying machine as an electrophotographic apparatus in the present embodiment (hereinafter simply referred to as a copying machine)
As shown in FIG. 2, the apparatus includes a copier main body 1 as an electrophotographic apparatus main body, and a reversal retransmission unit 2 provided as a reversal retransmission device provided below the copier main body 1.

As shown in FIG. 3, the main body 1 of the copying machine has an original mounting table 3 made of hard transparent glass on the upper surface, and an exposure optical system section 4 below the original mounting table 3. . The exposure optical system section 4 includes a lamp unit 5 that scans a document (not shown) placed on the document table 3 while irradiating the document with light, and a plurality of light guides that guide reflected light from the document to the photoconductor 8. And a lens unit 7 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, and an inter-image eraser (from the charging charger 9 in the rotation 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 are arranged in this order.

The above-mentioned intermediate transfer device 14 is used to transfer the transfer belt 1
7, rollers 18 and 19 for supporting the transfer belt 17
20, the transfer belt 17 is brought into pressure contact with the photoconductor 8,
A first transfer roller 21 for transferring the toner image formed on the surface to the transfer belt 17, and a second transfer for pressing the toner image on the surface of the transfer belt 17 onto the sheet when the toner image is transferred to the sheet by pressing the roller 20. A roller 22 and a cleaning device 23 for removing 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 supplying paper to the intermediate transfer device 14 at a predetermined timing are provided on the paper feed side of the intermediate transfer device 14. In the vicinity of the paper feed tray 25 and the paper feed tray 26, paper feed rollers 27, a transport roller 28 and the like are provided.

A suction unit 100 as a sheet conveying device, a fixing device 200, a switching gate 29, a paper discharge roller 30, and a paper discharge tray 31 are provided in the paper output direction from the intermediate transfer device 14.

As shown in FIG. 2, the resending conveyance path 32 extends to the intermediate tray 33 of the reversing resending unit 2, and conveys the sheet processed by the fixing device 200, and transfers the sheet to the toner image. The sheet is discharged onto the intermediate tray 33 with the formed surface facing upward. The sheets sent by the re-sending conveyance path 32 are stacked on the intermediate tray 33, and the sheets are sent to the re-sending conveyance path 35 by the sheet feeding roller 34. Retransmission transport path 35
Is configured to reverse the sheet sent from the intermediate tray 33 and to convey the sheet to the registration roller 24.

The suction unit 100 fixes the sheet to the fixing device 20 by a moving conveyor belt (not shown).
0, and as shown in FIG. 1, it is configured to rotate between an upper position and a lower position around an end portion on the paper input side. This upper position is a position where a sheet can be conveyed to an upper fixing unit described later in the fixing device 200,
The lower position is a position where the sheet can be conveyed to the lower fixing unit of the fixing device 200. The rotation operation to the upper and lower positions is performed by, for example, a cam mechanism provided on the lower surface side of the suction unit 100 or a solenoid.

As shown in FIG. 1, the fixing device 200 includes an upper heat roller 201 serving as an upper fixing roller, a middle heat roller 202 serving as a middle fixing roller, and a lower heat roller 202 serving as a lower fixing roller. And a heat roller 203. Upper heat roller 201 and middle heat roller 2
02, and the middle heat roller 202 and the lower heat roller 2
03 is pressed against, and the upper fixing portion formed at the pressure contact portion between the upper heat roller 201 and the middle heat roller 202 becomes a fixing portion at the time of full color copying, and is pressed against the pressure contact portion between the middle heat roller 202 and the lower heat roller 203. The formed lower fixing section is a fixing section for black and white copying. Therefore, the upper heat roller 201 is made of silicon rubber, the middle heat roller 202 is made of Teflon, and the lower heat roller 203 is made of silicon rubber or other suitable rubber. Note that the surface of the upper heat roller 201 is a very smooth surface in order to obtain high releasability from a three-layer toner image for obtaining a full-color image.

Each of the heat rollers 201 to 203 has a hollow shape, and a heater lamp 204 for heating is provided in each hollow portion. Upper or lower heat roller 201
Around the heaters 203 to 203, a thermistor 205 for detecting the surface temperature, a thermostat (not shown) for preventing overheating incorporated in the circuit of the heater lamp 204, and toner attached to the surfaces of the heat rollers 201 to 203 are provided. A cleaning roller 206 to be removed is provided. Further, around the middle and lower heat rollers 202 and 203, there are provided peeling claws 207 for peeling the paper from the roller surface, while around the upper heat roller 201, an oil application roller 208 impregnated with silicon oil. Is provided. The oil application roller 208 applies silicone oil to the surface of the upper heat roller 201 to prevent color toner from adhering to the surface of the heat roller, that is, to prevent offset, thereby ensuring the releasability of the color toner image, This is for giving gloss to the image. The oil application roller 208 is attached to one end of a roller holder 210 that rotates about a support shaft 209,
Eccentric cam 21 provided at the other end of roller holder 210
When the upper fixing unit is used by a driving mechanism including a tension spring 1 and a tension spring (not shown), the upper fixing unit is pressed against the upper heat roller 201.

The upper and lower heat rollers 201 to 2
The rotation of 03 is such that the middle heat roller 202 is driven, the upper and lower heat rollers 201 and 203 are driven, and the medium heat roller 202 rotates forward or backward depending on the fixing unit used.

An upper discharge conveyance path 41 is formed between the upper fixing section and the discharge roller 30, and a lower discharge conveyance path 42 is formed between the lower fixing section and the discharge roller 30. . The re-sending transport path 32 branches from the lower discharge transport path 42 and extends downward. The transport direction of the paper discharged from the lower fixing unit is changed to the lower discharge transport path at the branch portion of the transport paths 42 and 32. A switching gate 29 for switching between the path 42 and the retransmission path 32 is provided.

The copying machine is capable of performing one-sided copying of a black-and-white image and a full-color image, and two-sided copying of a black-and-white image, and copies a monochrome image on one side of a sheet.
Black-and-white / full-color double-sided copying as a single-color / full-color double-sided image forming operation for copying a full-color image on the opposite surface is possible. To perform these actions,
The copying machine body 1 includes a copying machine body 1 and a reversal retransmission unit 2.
Control device 51 shown in FIG.
Is provided. When black-and-white / full-color double-sided copying is selected by the copy selection key 52, the controller 51 first performs black-and-white copying on one side of the sheet,
Thereafter, the copier main body 1 and the reversing and retransmitting unit 2 are controlled so that full-color copying is performed on the opposite surface.

In the above configuration, first, a full-color copying operation in the copying machine will be described. After the full-color copy is selected by the copy selection key 52 shown in FIG. 4, when the copy start button 53 is turned on, the middle heat roller 202 rotates counterclockwise, and accordingly, the upper heat roller 201 rotates clockwise. Rotate around. In addition, the oil application roller 208 is
01, and the suction unit 100 moves to the upper position.

The surface of the photoconductor 8 rotating in the direction B is uniformly charged by the charging charger 9, and the first scanning of the original on the original mounting table 3 is performed by the exposure optical system 4. The reflected light from the original passes through a blue color separation filter (not shown) and a slit (not shown)
An exposure point on the surface of the photoconductor 8 is irradiated between the charger 9 and an inter-image eraser (not shown), and the photoconductor 8 is exposed to form an electrostatic latent image. Next, the photoconductor 8
Are 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 photoreceptor 8 is transferred to the transfer belt 17 circulating 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 charge removing device 16.

When the above series of operations is completed, the photosensitive member 8 is charged again by the charging charger 9, and the original is scanned by the exposure optical system unit 4 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 with magenta toner in the magenta developing tank 12. The magenta toner image formed on the surface of the photoconductor 8 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, similarly, a third scan is performed by the exposure optical system unit 4 using a red color separation filter, and a cyan toner image is formed on the photoconductor 8 by 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 operation so far, is
7, and a negative voltage higher than the surface potential of the transfer belt 17 is applied to the second transfer roller 22, so that the second transfer roller 22 is conveyed from the sheet cassette 25 or the sheet tray 26 via the registration roller 24. The three-layer toner image on the transfer belt 17 is transferred to the paper.

The sheet on which the toner image has been transferred is conveyed by the suction unit 100 to the upper fixing section between the upper heat roller 201 and the middle heat roller 202. In the upper fixing section, three layers of color toner images on paper are
It is heated and melted by the upper and middle heat rollers 201 and 202, and is fixed on paper. At this time, since silicon oil is supplied from the oil application roller 208 to the upper heat roller 201, offset of the toner image to the upper heat roller 201 is prevented, and gloss is given to the full-color toner image on the paper. You.

Next, the paper ejected from the upper fixing section of the fixing device 200 passes through the upper discharge conveyance path 41 to the discharge rollers 3.
0, and the discharge rollers 31
Is discharged on top.

Next, the black-and-white copying operation of the copying machine will be described. When the copy start button 53 is turned on after the black-and-white copy is selected by the copy selection key 52, the middle heat roller 202 rotates clockwise,
Accordingly, the lower heat roller 203 rotates counterclockwise. Further, the suction unit 100 moves to the lower position. The oil application roller 208 is separated from the upper heat roller 201.

The surface of the photosensitive member 8 is charged
And the scanning of the original on the original placing table 3 is performed by the exposure optical system unit 4. The reflected light from the document is guided to the exposure optical system 4 and irradiated to the photoconductor 8 without passing through the color separation filter and the slit, and an electrostatic latent image is formed on the photoconductor 8. Thereafter, the above-described electrostatic latent image is developed by the black developing tank 10, and the black toner image thus formed is transferred to the transfer belt 17,
It is further transferred to paper.

The sheet on which the toner image has been transferred is conveyed to the lower fixing section between the middle heat roller 202 and the lower heat roller 203 by the suction unit 100, and the toner image is fixed on the sheet.

Here, in the case of one-sided copying, the switching gate 29 operates so as to guide the sheet in the direction of the lower discharge conveying path 42, and the sheet discharged from the fixing device 200 is transferred to the lower discharging conveying path 42. The paper is then discharged onto a paper discharge tray 31 by a paper discharge roller 30.

On the other hand, in the case of double-sided copying, the switching gate 29 operates so as to guide the sheet in the direction of the re-feeding conveyance path 32, and the sheet output from the fixing device 200 is fed to the intermediate tray by the re-feeding conveyance path 32. 33 is discharged. Thereafter, the sheet on the intermediate tray 33 is sent out to the re-sending and conveying path 35 by the sheet feeding roller 34, is reversed by the re-sending and conveying path 35, and reaches the registration roller 24.

Next, the surface of the photoreceptor 8 is charged
The scanning is performed by the exposure optical system unit 4 on the document placed on the document placing table 3 upside down.
Next, a toner image is transferred to the back surface of the sheet by the same operation as described above, and the toner image is fixed on the sheet by the lower fixing unit. Thereafter, the sheet is guided toward the discharge roller 30 through the lower discharge conveyance path 42 by the switching gate 29 moving so as to guide the sheet toward the lower discharge conveyance path 42, and is discharged onto the discharge tray 31 by the discharge roller 30. Is discharged.

Next, the black-and-white / full-color double-sided copying operation in the copying machine will be described. Copy selection key 52
When the copy start button 53 is turned on after the monochrome / full-color double-sided copy is selected, the monochrome copy on one side of the sheet is first performed. That is, the middle heat roller 202 rotates clockwise, the lower heat roller 203 rotates counterclockwise, and the suction unit 100 moves to the lower position. In this state, the above-described black and white copy is performed, and the sheet on which the toner image has been transferred is subjected to a fixing process in a lower fixing unit. Fixing device 200
The above-mentioned sheet processed by the registration rollers 24 passes through the re-sending conveyance path 32, the intermediate tray 33 and the re-sending conveyance path 35.
Reach

Thereafter, a full-color copy is made on the opposite side of the sheet. That is, the middle heat roller 202
Rotates counterclockwise, and the upper heat roller 201 rotates clockwise accordingly.
08 is pressed against the upper heat roller 201, and the suction unit 100 moves to the upper position. In this state, the above-described full-color copying is performed.

As described above, in the copying machine, the fixing device 2
At 00, a fixing operation for full-color copying is performed in an upper fixing portion between the upper heat roller 201 and the middle heat roller 202, and a black and white copy is performed in a lower fixing portion between the middle heat roller 202 and the lower heat roller 203. The following advantages are obtained by performing the fixing operation in this case.

The fixing conditions of the upper and lower fixing sections can be individually set according to the black-and-white copy and the full-color copy, and the black-and-white copy and the full-color copy can be performed without performing complicated control on the fixing device 200. The best fixing operation can be performed in copying.

Since the fixing operation of the black and white copy is performed in the lower fixing section formed by the middle and lower heat rollers 202 and 203, which are durable and inexpensive, the frequency of replacing the upper and middle heat rollers 201 and 202 is reduced. Can be
In addition, the running cost in black-and-white copying can be reduced.

The paper processed in the lower fixing unit is hardly adhered to the silicon oil used in the upper heat roller 201, and the silicon oil adheres to the re-transport paths 32, 35 and the like, resulting in a reduction in the transport force. Paper jams and the above-mentioned silicone oil adhere to the photoreceptor 8 or the like, or each developing tank 1
No degradation in image quality or the like due to entering into 0-13.

In this copying machine, in the fixing device 200, a fixing operation for full-color copying is performed in an upper fixing portion formed on the upper side, and a black and white image is formed in a lower fixing portion formed on the lower side. Since the fixing operation is performed during the one-sided copy and the two-sided copy, the upper discharge transport path 41 and the lower discharge transport path 42
And the retransmission path 32 do not intersect, and the structure is simple.

In black-and-white / full-color double-sided copying, first, black-and-white copying is performed on one side of the sheet, and then full-color copying is performed on the opposite side. The toner layer is easily fixed and curled, and the full-color copied paper to which the silicone oil has adhered is not sent to the re-feeding conveyance paths 32 and 35 of the reversing and re-feeding unit 2. The occurrence of paper jams in the unit 2 and the above-described deterioration in image quality due to silicone oil are prevented.

[0048]

EFFECT OF THE INVENTION The electrophotographic apparatus according to claim 1 of the present invention, as described above, the electrophotographic apparatus main body, and the upper fixing section for full-color image formation, a lower fixing portion for monochromatic image formation,
A discharge conveyance path on for conveying the upper fixing portion of the sheet to the outside, and the lower discharge transport path for transporting the lower fixing portion of the sheet to the outside, for conveying from the lower fixing portion of the sheet to the reversing retransmission device Re-feeding transport path, these lower discharge transport paths and re-feeding
It is provided at the branch from the paper feed path, and is a sheet discharged from the lower fixing section.
Switch the transport direction of the sheet to the lower discharge transport path or the retransmission transport path.
And a switching gate for switching . Ma
The electrophotographic apparatus according to claim 2 of the present invention has
In the first configuration, a single-color image is formed on one surface of the sheet
To form a full-color image on the opposite side
Color double-sided image forming operation is possible, and this single color / full
When the color double-sided image forming operation is performed, the above control is performed.
The means first includes forming a monochrome image on one side of the sheet.
Then a full-color image is formed on the opposite side
As described above, the main body of the above-described electrophotographic apparatus and the reversing retransmission device are controlled.
It is a configuration to control.

Thus, the fixing conditions of the upper and lower fixing units can be individually set for full-color image formation and for a single-color image, that is, for black-and-white image formation. The best fixing operation can be performed on a full-color image and a black-and-white image without performing any appropriate control. In addition, since a durable and inexpensive fixing roller can be used for forming the lower fixing portion for forming a black and white image, the frequency of replacing the fixing roller can be reduced, and the running cost in forming a black and white image is reduced. can do. Further, the oil used in the upper fixing roller is less likely to adhere to the sheet processed in the lower fixing unit, and paper jam and deterioration in image quality due to the oil can be avoided. Further, the upper discharge transport path, the lower discharge transport path, and the retransmission transport path do not intersect, and the structure is simple. In the case of a single-color / full-color double-sided image forming operation, first, a single-color image is formed on one surface of the sheet, and then a full-color image is formed on the opposite surface.
It is possible to prevent paper jam due to curled paper, paper jam caused by oil, and deterioration of image quality.

[Brief description of the drawings]

FIG. 1, showing an embodiment of the present invention, is a view showing a configuration near a fixing device of a copying machine.

FIG. 2 is an overall configuration diagram of a copier including the above-described fixing device.

FIG. 3 is an enlarged view of the copying machine main body shown in FIG. 2;

FIG. 4 is a schematic block diagram showing a main part of a control system of the copying machine.

FIG. 5 is an overall configuration diagram showing a conventional copying machine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Copier main body (electrophotographic apparatus main body) 2 Reverse retransmission unit (reversal retransmission device) 32 Retransmission transport path 35 Retransmission transport path 41 Upper discharge transport path 42 Lower discharge transport path 51 Control device (Control means) 52 Copy selection key 100 Suction Unit (sheet conveying device) 200 Fixing device 201 Upper heat roller (Upper fixing roller) 202 Medium heat roller (Medium fixing roller) 203 Lower heat roller (Lower fixing roller) 208 Oil application roller

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Hidetoshi Kaneko 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (56) References JP-A-4-52674 (JP, A) JP-A-4- 157482 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G03G 13/20 G03G 15/20

Claims (2)

(57) [Claims] 1. An electrophotographic apparatus main body for forming a single-color or full-color image on a sheet, and a reversal re-feed for reversing a sheet discharged from the electrophotographic apparatus main body and supplying the inverted sheet to the electrophotographic apparatus main body. And the main body of the electrophotographic apparatus
In an electrophotographic apparatus provided with a control means for controlling the reversing retransmission device, the main body of the electrophotographic apparatus comprises an upper fixing portion of the full-color image formation, for monochrome image formation
A lower fixing portion, for conveying from the upper fixing portion of the sheet to the outside
An upper discharge conveyance path , a lower discharge conveyance path for conveying a sheet from the lower fixing unit to the outside , a retransmission conveyance path for conveying a sheet from the lower fixing unit to the reversing and retransmission device, and these lower discharge conveyance paths. Provided at the branch from the retransmission path
And the sheet discharged from the lower fixing unit is discharged downward in the conveyance direction.
An electrophotographic apparatus comprising a switching gate for switching to a transport path or a retransmission transport path . 2. A single-color image is formed on one side of a sheet.
/ Full color to form a full color image on the opposite side of
When double-sided image forming operation is possible and this single-color / full-color double-sided image forming operation is performed
First, the control means first applies a single color to one surface of the sheet.
An image is formed, then a full-color image on the opposite side
The above electrophotographic apparatus body and the reversible
2. The control device according to claim 1, wherein
Electrophotographic equipment.