JPH09258602A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eject transfer material without necessitating a complicated switching mechanism and to prevent a toner image on the lower surface of the transfer material from being rubbed by changing the order of pages formed on both sides of the transfer material in accordance with the change of the transfer order or the output order of image data or the change of ejection form. SOLUTION: The process of a color image forming device is controlled and executed by accessing one mode selected from programs P1 to P4 corresponding to 1st to 4th modes stored in a ROM through a control part in a RAM in accordance with an external signal showing the transfer order of the image data or the designation of page output order from the operation part of a device main body or the selection of the mode such as face-down/face-up paper ejection. Thus, both-side image paginated is outputted in accordance with the transfer order or the output order of the image data and the ejection form without necessitating a both-side reverse paper supply device used in the conventional manner.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine which arranges a charging means, an image exposing means and a developing means around an image carrier to transfer and fix a toner image formed on the image carrier onto a transfer material. The present invention relates to an electrophotographic image forming apparatus such as a printer, a FAX, or the like.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus such as a copying machine, a printer, and a FAX, a toner image formed on an image carrier is transferred onto a transfer material, fixed, and then discharged. A method of discharging the toner image surface on the material upward (face up) or a method of discharging the toner image surface on the transfer material downward (face down) is used.

When performing double-sided copying, the image on one side formed on the image carrier is transferred and fixed on a transfer material, which is once housed in a double-sided reversing paper feeding device and then re-imaged. A method is used in which a transfer material is fed from a double-sided reverse paper feeding device in time with an image formed on a carrier, and the image on the other surface is transferred and fixed on the transfer material.

As described above, in this double-sided copying apparatus, since the transfer material is fed to the double-sided reversal sheet feeding apparatus and is passed through the fixing apparatus twice, the reliability of the transfer material is low, and the jam occurs. It was a cause of causing such. In contrast, JP-B-49-37538 and JP-B-54-28740.
And JP-A-1-44457 and JP-A-4-21
Japanese Patent Laid-Open No. 4445/1992 proposes a method in which after fixing both surfaces of a transfer material, fixing is carried out once.
No. 7, JP-A-4-214576, etc., an image forming unit including an image carrier, a charging unit, an image exposing unit, a developing unit and the like is arranged in parallel on a plurality of sets of toner image receiving bodies to form a color image. Methods have been proposed for making double-sided copies.

[0005]

However, in one image forming apparatus, the toner image surface on the transfer material is discharged upward (face up) or the toner image surface on the transfer material is discharged downward (face up). Down), the page order is not aligned. Further, page alignment can be performed when it is desired to change the transfer order of image data, or when the transfer order of the image data is specified by the ADF or the like because the transfer order of either the previous page or the subsequent page is specified. There was a problem that disappeared.

Further, in the double-sided color image formation proposed by the above-mentioned JP-A-1-44457 and JP-A-4-214576, although the transfer material transporting property is improved, it is possible to form a single image on the toner image receiving body. Since the color toner images are superposed one by one, image deterioration such as color misregistration, toner scattering, and rubbing easily occurs.

Further, when an attempt is made to convey a transfer material having a toner image formed below the transfer material on one side or both sides, the toner image is rubbed in the conveying portion, which causes a defective image.

The present invention solves the above problems and provides an image forming apparatus in which the transfer material is discharged without a complicated switching mechanism and the toner image on the lower surface of the transfer material is not rubbed. To aim.

[0009]

The above object is to directly transfer a toner image formed on an image carrier to a transfer material, while temporarily transferring a toner image formed on the image carrier to a toner image receiver. After that, in an image forming apparatus that transfers the toner image to both surfaces of the transfer material by transferring it to a transfer material, and fixes and discharges the toner image, the transfer order or the output order of the image data is changed or the discharge mode is changed. This is achieved by an image forming apparatus characterized by changing the order of pages formed on both surfaces of a transfer material (first invention).

Another object of the present invention is to provide an image forming apparatus having a carrying section for carrying a toner image formed on an image bearing member onto a transfer material and then carrying the toner image-adhered surface downward. The invention is achieved by an image forming apparatus characterized in that a spur having a sharp tip is provided in the carrying section along the carrying direction (second invention).

[0011]

Embodiments of the present invention will be described below. Note that the description in this column does not limit the technical scope of the claims and the meaning of terms. Also, the following assertive description in the embodiment of the present invention indicates the best mode, and does not limit the meaning of the terms of the present invention or the technical scope.

Embodiment 1 The image forming process and each mechanism of the first embodiment of the image forming apparatus of the present invention will be described with reference to the color image forming apparatus shown in FIGS. 1 is a sectional configuration diagram of a color image forming apparatus of a first embodiment of the image forming apparatus of the present invention, FIG. 2 is a side sectional view of the image carrier of FIG. 1, and FIG. FIG. 4 is a diagram showing a 1-mode image forming state, and FIG.
5 is a diagram showing an image forming state in a second mode, and FIG.
FIG. 5 is a diagram showing a double-sided image forming state relating to the third mode and the fourth mode, FIG. 5 (A) is a diagram showing an example of double-sided image formation, and FIG. 5 (B) is a diagram showing double-sided image formation. FIG. 6 is a diagram showing another example, FIG. 6 is a circuit block diagram showing various mode selections in the color image forming apparatus of the first embodiment, and FIG. 7 is a diagram showing another example of the discharging method. .

As shown in FIG. 6, the first to fourth modes of the image forming method of the color image forming apparatus described below are selected. Corresponds to the first mode stored in the ROM through the control unit by specifying an external signal indicating the transfer order of image data or specifying the page output order from the operation unit of the main body of the device or mode selection such as face-down / face-up discharge Program P1 to be executed, program P corresponding to the second mode
2. One mode selected from the program P3 corresponding to the second and third modes and the program P4 corresponding to the fourth mode is called into the RAM, and the process control and execution of the color image forming apparatus are performed.

First, the first mode will be described with reference to FIGS.

The photosensitive drum 10, which is an image bearing member, is provided with a cylindrical substrate formed of a transparent member such as glass or transparent acrylic resin inside, and a transparent conductive layer a-
A photosensitive layer such as a Si layer or an organic photosensitive layer (OPC) is formed on the outer periphery of the substrate.

The photosensitive drum 10 is sandwiched by a front flange 10a and a rear flange 10b, and the front flange 10a is supported by bearings by guide pins 10P1 provided on a cover 103 attached to a front side plate 101 of the apparatus main body.
The rear flange 10b is fitted onto a plurality of guide rollers 10R attached to the rear side plate 102 of the main body of the apparatus to hold the photosensitive drum 10. A gear 10G provided on the outer periphery of the rear flange 10b is meshed with a driving gear G1, and the power of the gear 10G rotates the photosensitive drum 10 in a clockwise direction indicated by an arrow in FIG. 1 with the transparent conductive layer being grounded. It

In the present embodiment, it is sufficient that the photoconductive layer of the photosensitive drum has an exposure light amount capable of imparting an appropriate contrast. Therefore, the light transmittance of the transparent substrate of the photosensitive drum in the present embodiment does not need to be 100%, and may have a characteristic that some light is absorbed when the exposure beam is transmitted. As the material of the translucent substrate, an acrylic resin, particularly one polymerized using methyl methacrylate monomer, has transparency, strength, accuracy,
Acrylic, fluorine used for other general optical members, etc.
Various translucent resins such as polyester, polycarbonate, and polyethylene terephthalate can be used. Further, as long as it has a light-transmitting property with respect to the exposure light, it may be colored. The light-transmitting conductive layer is made of indium-tin-oxide (ITO), tin oxide, lead oxide, indium oxide, copper iodide, or a light-transparent metal thin film made of Au, Ag, Ni, Al, or the like. As a film forming method, a vacuum evaporation method, an active reaction evaporation method, various sputtering methods, various CVD methods, a dip coating method, a spray coating method, and the like are used. As the photoconductor layer, an amorphous silicon (a-Si) alloy photosensitive layer, an amorphous selenium alloy photosensitive layer, or various organic photosensitive layers (OPC) can be used.

Scorotron charger 11 as charging means
Is used in an image forming process of each color of yellow (Y), magenta (M), cyan (C) and black (K), and is exposed in a direction orthogonal to a moving direction of the photosensitive drum 10 as an image carrier. It is installed facing the body drum 10,
A charging operation is performed by a control grid maintained at a predetermined potential with respect to the above-described organic photoconductor layer of the photoconductor drum 10 and a corona discharge having the same polarity as the toner using, for example, a sawtooth electrode as the discharge electrode 11a (this embodiment). , A uniform potential is applied to the photosensitive drum 10. Other wire electrodes can be used as the discharge electrode 11a.

The exposure unit 12 as an image exposure means for each color is arranged such that the exposure position on the photosensitive drum 10 is between the discharge electrode 11a of the scorotron charger 11 and the developing position of the developing device 13 and a developing sleeve 131. With respect to the photoconductor drum, the photoconductor drum is arranged on the upstream side in the rotation direction.

The exposure unit 12 is a linear exposure element 12a in which a plurality of LEDs (light emitting diodes) as image exposure light emitting elements arranged in the main scanning direction parallel to the axis of the photosensitive drum 10 are arranged in an array. And a SELFOC lens 12b as an equal-magnification imaging element are configured as an exposure unit attached to a holder (not shown). Exposure for each color is performed on a cylindrical holding member 20 fixed with guide pins 10P2 provided on the rear plate 102 of the apparatus main body and guide pins 10P1 provided on the cover 103 attached to the front plate 101 as guides. Unit 12, uniform exposure device 1
2c and a transfer simultaneous exposure device 12d are attached and housed inside the substrate of the photoconductor drum 10. Image data of each color read by a separate image reading device and stored in the memory is sequentially read from the memory and input to the exposure unit 12 for each color as an electric signal.

As the exposure element, a linear element in which a plurality of light emitting elements such as FL (fluorescent substance light emission), EL (electroluminescence), PL (plasma discharge), LED (light emitting diode) are arranged in an array is also used. Used. The emission wavelength of the light emitting element used in this embodiment is usually Y,
A range of 680 to 900 nm, which has a high transmittance of the M and C toners, is preferable, but a shorter wavelength which does not have sufficient transparency for the color toner since image exposure is performed from the back surface may be used.

In the present embodiment, the developing device provided in accordance with the color order in which images are formed and the rotating photosensitive drum is arranged in the rotating direction of the photosensitive drum 10 shown by the arrow in FIG. On the other hand, the Y and M developing devices 13 are arranged on the left side of the photoconductor drum 10, and the C and K developing devices 13 are arranged on the right side of the photoconductor drum 10. The Y and M scorotron chargers 11 are arranged below, and the C and K scorotron chargers 11 are arranged above the developing casing 138 of the C and K developing units 13.

The developing device 13, which is a developing means for each color, contains one-component or two-component developers of yellow (Y), magenta (M), cyan (C) and black (K), respectively, and is exposed to light. Rotating in the same direction as the rotation direction of the photoconductor drum 10 at the developing position while maintaining a predetermined gap with respect to the peripheral surface of the body drum 10, for example, 0.5 mm to 1 m in thickness.
The developing sleeve 131 is made of cylindrical non-magnetic stainless steel or aluminum and has an outer diameter of 15 to 25 mm.

The developing unit 13 is moved to a predetermined distance from the photosensitive drum 10 by an abutting roller (not shown), for example, 100 μm.
.About.1000 .mu.m and kept in a non-contact state, and when developing by the developing device 13 for each color, the developing sleeve 131
A developing bias to which a DC voltage or an AC voltage AC is further applied is applied to the photosensitive drum, a jumping development is performed with a one-component or two-component developer contained in the developing device, and a negatively charged photosensitive member grounds the transparent conductive layer. The same polarity as the toner for the drum 10 (minus polarity in this embodiment)
Is applied, and non-contact reversal development is performed in which toner is adhered to an exposed portion.

The developing device 13 for each color described above applies a developing bias voltage to the electrostatic latent image formed on the photosensitive drum 10 formed by the charging by the scorotron charger 11 and the image exposure by the exposure unit 12 described above. The toner having the same polarity as the charging polarity in a non-contact state by the non-contact developing method according to (the photosensitive drum in this embodiment is negatively charged,
Reversal development is carried out with a negative polarity toner).

An image read by an image sensor of an image reading apparatus separate from the apparatus or an image edited by a computer is temporarily stored as image data for each of Y, M, C and K as an original image. And stored.

A gear 10 provided on the rear flange 10b of the photoconductor drum 10 is driven through a drive gear G1 by starting a photoconductor drive motor (not shown) when image recording is started.
G is rotated to rotate the photosensitive drum 10 in the clockwise direction indicated by the arrow in FIG. 1, and at the same time, Y disposed below the developing casing 138 of the yellow (Y) developing device 13 to the left of the photosensitive drum 10. The application of a potential to the photosensitive drum 10 is started by the charging action of the scorotron charger 11 described above.

After the photosensitive drum 10 is applied with an electric potential, the Y exposure unit 12 starts exposure by an electric signal corresponding to the first color signal, that is, Y image data, and the surface of the photosensitive drum 10 is exposed to light by rotational scanning of the drum. An electrostatic latent image corresponding to the Y image of the original image is formed on the layer.

The latent image is reversal-developed by the Y developing device 13 in a state where the developer on the developing sleeve is not in contact with the developer, and a yellow (Y) toner image is formed in accordance with the rotation of the photosensitive drum 10.

Next, the photosensitive drum 10 has a magenta (M) developing unit 1 on the yellow (Y) toner image and further on the left of the photosensitive drum 10 and above the yellow (Y).
3 is provided with a potential by the charging action of the magenta (M) scorotron charger 11 disposed below the developing casing 138, and an electric signal corresponding to the second color signal of the M exposure unit 12, that is, the image data of M. Exposure is performed by non-contact reversal development by the developing device 13 of M, and magenta (M) is formed on the yellow (Y) toner image.
Toner images are sequentially superposed and formed.

By the same process, the developing casing 13 of the cyan (C) developing device 13 is provided on the right side of the photosensitive drum 10.
The cyan (C) toner image corresponding to the third color signal is further obtained by the cyan (C) scorotron charger 11, the exposure unit 12 of C, and the developing unit 13 of C, which are arranged above the photoconductor 8 The black (K) scorotron charger 11, the exposure unit 12, and the developing device 13 are arranged on the right side of the drum 10 and below the developing casing 138 of the black (K) developing device 13 at the lower part of the fourth color by the fourth unit. A black (K) toner image corresponding to the signal is sequentially superposed, and a color toner image is formed on the peripheral surface within one rotation of the photosensitive drum 10 (toner image forming means).

These Y, M, C and K exposure units 1
Exposure of the organic photosensitive layer of the photosensitive drum 10 by 2 is performed from the inside of the drum through the transparent substrate described above. Therefore, the exposure of the images corresponding to the second, third, and fourth color signals is performed without any influence from the previously formed toner image, and the same exposure as the image corresponding to the first color signal is performed. It is possible to form an electrostatic latent image. In order to stabilize the temperature inside the photosensitive drum 10 and prevent the temperature from rising due to the heat generated by each exposure optical system 12, a material having good thermal conductivity is used for the holding member 20, and a heater 201 is used when the temperature is low. When the temperature is high, it can be suppressed to a level without any trouble by taking measures such as radiating heat to the outside through the heat pipe 202.

The recording paper P, which is a transfer material, is sent out by a feed roller 15a from a paper feed cassette 15, which is a transfer material storage means, is fed by a feed roller 15b, and is conveyed to a timing roller 15c.

The recording paper P is driven by a timing roller 15c to form a toner image forming means on the photosensitive drum 10.
The color toner image carried on the (first image carrying means) is synchronized with the driving roller 14d and the driven roller 14e.
The toner image receiving body 14a, which is stretched between the photosensitive drums 10 and provided close to or in contact with the photosensitive drum 10, conveys the toner image receiving body 14a to the transfer area 14b. At this time, the recording paper P is charged to the same polarity as the toner by the paper charger 14f, adsorbed to the toner image receiving body 14a, and fed to the transfer area 14b.
By charging the paper with the same polarity as that of the toner, it is possible to prevent the toner image on the toner image receiving body and the toner image on the image carrier from being attracted to each other, thereby preventing the toner image from being disturbed.

The color toner images carried on the peripheral surface of the photoconductor drum 10 by the transfer device 14c to which a voltage having a polarity opposite to that of the toner (in this embodiment, a positive polarity) is applied are collectively on the upper surface of the recording paper P. Is transferred to the side (first transfer means). During the transfer by the transfer unit 14c, the photosensitive drum 10 is opposed to the transfer unit 14c so that good transfer is performed.
Uniform exposure is performed by a transfer simultaneous exposure device 12d provided inside the device, for example, using a light emitting diode.

Since the toner images of the respective colors overlap each other, it is preferable that the upper and lower toner layers of the toner layer are charged to the same polarity with the same charge amount in order to enable batch transfer. Therefore, in a double-sided image formation in which the polarity of the color toner image formed on the toner image receiving member 14a is inverted by corona charging or the polarity of the color toner image formed on the image carrier is inverted by corona charging, the lower layer is formed. The toner is not sufficiently charged to the same polarity, so that the transfer becomes unfavorable.

Repeated reversal development on the image carrier, the color toner images of the same polarity formed by superposition are collectively transferred to the toner image receiver 14a without changing the polarity, and then the recording paper without changing the polarity. The batch transfer to P is preferable because it contributes to the improvement of transferability in the back side image formation. Also for the surface image formation, reversal development is repeatedly performed on the image carrier, and the color toner images of the same polarity formed by superimposition are collectively transferred to the recording paper P without changing the polarity. It is preferable because it contributes to improvement of the property.

As described above, in the color image formation, the first transfer means is operated to form a color toner image on the surface of the transfer material by using the above-described image forming method for the front surface and the back surface. A two-sided image forming method of forming a color toner image on the back surface of the transfer material by operating the second transfer means is preferably employed.

The toner image receiver 14a has a thickness of 0.5-2.
An endless rubber belt of 0 mm, a semiconductive substrate of silicon rubber or urethane rubber having a resistance value of 10 ⁸ to 10 ¹² Ω · cm, and a thickness of 5 μm to 50 μm as a toner filming prevention layer outside the rubber substrate. And a two-layer structure with fluorine coating. This layer also preferably has a similar semiconductivity. 0.1-thick instead of rubber belt base
0.5mm semiconductive polyester or polystyrene,
Polyethylene, polyethylene terephthalate and the like can also be used.

After the transfer, the toner remaining on the peripheral surface of the photosensitive drum 10 is discharged to the cleaning device 19 after being discharged by the image carrier AC static eliminator 16.
Cleaning blade 19a made of a rubber material abutting against
In order to eliminate the history of the photoconductor until the previous print, the peripheral surface of the photoconductor is erased by exposure by the uniform exposure device 12c before charging using a light emitting diode, and the charge at the time of previous printing Are removed and the next color image formation is continued.

The recording paper P having the color toner image formed on the upper surface thereof is neutralized by the paper separation AC neutralizer 14h for separating the transfer material, separated from the toner image receiving body 14a, and heaters are installed inside both rollers. The sheet is conveyed to the fixing device 17, which is composed of two rollers. Fixing roller 17a
By applying heat and pressure between the pressure roller 17b and the pressure-bonding roller 17b, the adhered toner on the recording paper P is fixed, and the recording paper P on which the image is recorded is sent by the paper discharge roller 18 and The toner image is ejected to the external tray with the image side facing up (face up).

The above is the image forming method in the first mode. However, in the case where a large number of copies, for example, n copies are made in the first mode, as shown in FIG. Ejection is performed and the first copy is ejected on the uppermost surface with the color toner image surface facing upward.

The toner remaining on the peripheral surface of the toner image receiver 14a after the transfer is the toner image receiver cleaning device 14i.
Cleaning. The toner remaining on the peripheral surface of the photosensitive drum 10 after the transfer is transferred to the image carrier AC static eliminator 1.
After being discharged by 6, the cleaning device 19 is scraped into the cleaning device 19 by the cleaning blade 19a made of a rubber material which is in contact with the photosensitive drum 10, and is collected by a screw 19b in a toner discharge container (not shown). To be done. The photoconductor drum 10 from which the residual toner has been removed by the cleaning device 19 is uniformly charged by the Y scorotron charger 11, and enters the next image forming cycle.

Next, the image forming method in the second mode will be described with reference to FIGS. 4 and 1.

By the image forming process by the toner image forming means described in the first mode, a superposed color toner image is formed on the photosensitive drum 10 (first image carrying means) as an image bearing body, In the transfer area 14b, the superimposed color toner image on the drum 10 is stretched between the driving roller 14d and the driven roller 14e by the transfer device 14c to which a voltage having the opposite polarity (plus polarity in this embodiment) to the toner is applied. And the toner image receiving body 14a provided close to or in contact with the photosensitive drum 10.
(Second image carrying means) are collectively transferred onto (second image carrying means). At this time, for example, uniform exposure is performed by the simultaneous transfer exposure device 12d using a light emitting diode so that good transfer is performed. At this time, it is necessary to change the image data so that the color toner image formed in the second mode and the color toner image formed in the first mode on the image carrier are mirror images of each other.

After the transfer, the toner remaining on the peripheral surface of the photosensitive drum 10 is discharged to the cleaning device 19 after being discharged by the image carrier AC static eliminator 16.
Cleaning blade 19a made of a rubber material abutting against
In order to eliminate the history of the photoconductor until the previous print, the peripheral surface of the photoconductor is erased by exposure by the uniform exposure device 12c before charging using a light emitting diode, and the charge at the time of previous printing Are removed and the next color image formation is continued.

The recording paper P, which is a transfer material, is sent from the paper feed cassette 15 that is a transfer material storage means by the sending roller 15a, is fed by the feeding roller 15b, and is conveyed to the timing roller 15c.

The recording paper P is fed to the transfer area 14b in synchronization with the color toner image carried on the toner image receiving body 14a by driving the timing roller 15c. At this time, the recording paper P is charged to the same polarity as the toner by the paper charger 14f, adsorbed to the toner image receiving body 14a, and fed to the transfer area 14b. By charging the paper with the same polarity as that of the toner, it is possible to prevent the toner image on the toner image receiving body and the toner image on the image carrier from being attracted to each other, thereby preventing the toner image from being disturbed.

A toner image on the peripheral surface of the toner image receiving body 14a is collectively applied to the lower surface side of the recording paper P by the back surface transfer device 14g to which a voltage having a polarity opposite to that of the toner (positive polarity in this embodiment) is applied. Transfer (second transfer means).

The recording paper P on which the color toner image is formed on the lower surface is neutralized by the paper separation AC static eliminator 14h for separating the transfer material, separated from the toner image receiving body 14a, and heaters are installed inside both rollers. The sheet is conveyed to a fixing device 17, which is a fixing unit including two rollers.
By applying heat and pressure between the fixing roller 17a and the pressure-bonding roller 17b, the adhered toner on the lower surface of the recording paper P is fixed, and the recording paper P having the image recorded on the lower surface is discharged by the discharge roller 18. The toner image surface is sent to the tray outside the apparatus with the toner image side facing down (face down) and discharged.

Although the above is the image forming method in the second mode, when a large number of sheets, for example, n sheets are copied in the second mode, as shown in FIG. Ejection is performed and the nth copy is ejected to the uppermost surface with the color toner image surface facing down.

The toner remaining on the peripheral surface of the toner image receiver 14a after the transfer is removed from the toner image receiver cleaning device 14i.
Cleaning. The toner remaining on the peripheral surface of the photosensitive drum 10 after the transfer is transferred to the image carrier AC static eliminator 1.
After being discharged by 6, the cleaning device 19 is scraped into the cleaning device 19 by the cleaning blade 19a made of a rubber material which is in contact with the photosensitive drum 10, and is collected by a screw 19b in a toner discharge container (not shown). To be done. The photoconductor drum 10 from which the residual toner has been removed by the cleaning device 19 is uniformly charged by the Y scorotron charger 11, and enters the next image forming cycle.

As described above, with the change of the first mode and the second mode, it is necessary to make the image data on one side a mirror image, and to change the page output order, in other words, the image data transfer order. That is, if there is a designation or restriction in the transfer order of the image data, the first mode or the second mode is selected according to the specification or restriction.

Next, the image forming method in the third mode will be described with reference to FIG.

By the image forming process of the toner image forming means described in the first mode, a superposed color toner image as a back side image is formed on the photosensitive drum 10 (first image carrying means) as an image bearing member. And photoconductor drum 1
Transfer area 1 of the superposed color toner image
In 4b, a transfer device 14c to which a voltage having a polarity (plus polarity in the present embodiment) opposite to that of the toner is applied is stretched between the driving roller 14d and the driven roller 14e, and comes close to or comes into contact with the photosensitive drum 10. The images are collectively transferred onto the provided toner image receiver 14a (second image carrier). At this time, the transfer simultaneous exposure device 12 using, for example, a light emitting diode is used so that good transfer is performed.
Uniform exposure by d is performed.

After the transfer, the toner remaining on the peripheral surface of the photoconductor drum 10 is discharged to the cleaning device 19 after being discharged by the image carrier AC charge remover 16.
Cleaning blade 19a made of a rubber material abutting against
In order to eliminate the history of the photoreceptor up to the previous print, the peripheral surface of the photoreceptor is removed by, for example, exposure by a uniform exposure unit 12c before charging using a light emitting diode, and the charge at the previous print is removed. Is removed and the next color image formation of the front surface image is performed.

The back side image formed on the toner image receiving body 14a and the transfer area 14b are synchronized with each other, and the front side image of the superimposed color toner image is formed again on the photosensitive drum 10 by the toner image forming means. It It is necessary to change the image data so that the front side image formed at this time is a mirror image of the back side image formation on the image carrier.

The recording paper P, which is a transfer material, is sent from the paper feed cassette 15 which is a transfer material storage means by the sending roller 15a, is fed by the feeding roller 15b, and is conveyed to the timing roller 15c.

The recording paper P is driven by the timing roller 15c, and the color toner image of the front surface image carried on the photosensitive drum 10 and the color toner image of the back surface image carried on the toner image receiving body 14a are formed. Are synchronized and fed to the transfer area 14b. At this time, the recording paper P is charged to the same polarity as the toner by the paper charger 14f, adsorbed to the toner image receiving body 14a, and fed to the transfer area 14b. By charging the paper with the same polarity as that of the toner, it is possible to prevent the toner image on the toner image receiving body and the toner image on the image carrier from being attracted to each other, thereby preventing the toner image from being disturbed.

The surface image on the peripheral surface of the photoconductor drum 10 is collectively recorded on the recording paper P by the transfer device 14c to which the voltage of the opposite polarity (plus polarity in this embodiment) to the toner is applied.
(First transfer means). At this time, the back surface image on the peripheral surface of the toner image receiver 14a is not transferred to the recording paper P but exists on the toner image receiver 14a. next,
Polarity opposite to toner (positive polarity in this embodiment)
The transfer of the back surface image on the peripheral surface of the toner image receiving body 14a to the lower surface side of the recording paper P is collectively performed by the back surface transfer device 14g to which the above voltage is applied (second transfer means). At the time of transfer by the transfer device 14c, the transfer device 14c
Uniform exposure is performed by a transfer simultaneous exposure device 12d, which is provided inside the photosensitive drum 10 so as to face the above, and uses, for example, a light emitting diode.

The recording paper P on which the color toner images are formed on both sides is neutralized by the paper separation AC neutralizer 14h for separating the transfer material, separated from the toner image receiver 14a, and heaters are installed inside both rollers. The sheet is conveyed to a fixing device 17, which is a fixing unit including two rollers.
By applying heat and pressure between the fixing roller 17a and the pressure roller 17b, the toner adhered to the front and back of the recording paper P is fixed, and the recording paper P on which double-sided image recording has been performed is sent by the paper discharge roller 18. And discharged to a tray outside the apparatus.

The above is the image forming method in the third mode. As shown in FIG. 5A, when a large number of sheets, for example, n pages (n is an even number) are copied in the third mode. , The odd-numbered page color toner image formed on the photosensitive drum 10 and the even-page color toner image formed on the toner image receiving body 14a are double-sided images, and the n-th page color toner image is faced down. Images are formed and discharged from the double-sided copies of pages n and n-1, and the first copy is on the uppermost surface with the color toner image on the second page facing down and the toner image surface on the first page facing up. Is discharged.

The toner remaining on the peripheral surface of the toner image receiving body 14a after the transfer is the toner image receiving body cleaning device 14i.
Cleaning. The toner remaining on the peripheral surface of the photosensitive drum 10 after the transfer is transferred to the image carrier AC static eliminator 1.
After being discharged by 6, the cleaning device 19 is scraped into the cleaning device 19 by the cleaning blade 19a made of a rubber material which is in contact with the photosensitive drum 10, and is collected by a screw 19b in a toner discharge container (not shown). To be done. The photoconductor drum 10 from which the residual toner has been removed by the cleaning device 19 is uniformly charged by the Y scorotron charger 11, and enters the next image forming cycle.

Similarly, in the image formation in the fourth mode, as shown in FIG. 5B, for example, n pages (n is an even number).
Of the even number of pages and the toner image receiver 14a formed on the photoconductor drum 10 when the copying is performed.
The odd-numbered page color toner image formed above is used as a double-sided image, and the color toner image of the first page is turned down, and image formation and discharge are performed from a double-sided copy of the first and second pages. The copy is ejected on the uppermost surface with the color toner image on the n-1th page down and the color toner image surface on the nth page up.

As described above, in accordance with the change of the third mode and the fourth mode, it is necessary to make the image data on one side a mirror image and to change the page output order, in other words, the image data transfer order. That is, if there is a designation or restriction in the transfer order of the image data, the third mode or the fourth mode is selected according to the specification or restriction.

With the above-described third and fourth mode double-sided image forming methods, there is no need for a double-sided reversal sheet feeding device used conventionally, and since the fixing device only needs to be passed through once, the transfer material can be conveyed reliably. It is highly likely. Further, since the superimposed color toner images are transferred in a batch, color deviation of the color image on the toner image receiving body, toner scattering, rubbing, etc. are unlikely to occur, and good double-sided color image formation with little image deterioration is performed.

As shown in FIG. 7, the discharge port of the recording paper P is switched so that the photosensitive drum 10 and the toner image receiving body 14a are changed.
The color toner image formed on the recording paper P is transferred onto the recording paper P, fixed through a fixing device 17 as a fixing means, then reversed and conveyed, and is sent by a paper discharge roller 18 and discharged to a tray outside the device. It is something. Figure 3 ~
Since the front and back of the discharged recording paper P are opposite to those described in FIG. 5, the output order of the pages described in FIGS. 3 to 5 is reversed. This will be described in detail in Embodiment 4.

Due to the user's convenience, even when the discharge form is changed, it is necessary to change the output order of pages in which single-sided image data is a mirror image, in other words, the transfer order of image data. That is, the first mode → the second mode, the second mode → the first mode or the third mode → the fourth mode, the fourth mode → the third mode are combined with the restriction or change of the transfer order of the image data according to the discharge mode. Will be selected.

Embodiment 2 The second embodiment is one in which a conveying section is provided between the toner image receiver and the fixing device of the color image forming apparatus described in the first embodiment. The second embodiment will be described with reference to FIGS. 8 is a diagram showing an example of the transport unit, FIG. 9 is a top view of the transport unit in FIG. 8, and FIG.
FIG. 11 is a perspective view of a spur, FIG. 11 is a view showing another example of the spur, FIG. 11 (A) is a sectional view showing another example of the spur, and FIG. It is a perspective view which shows the other example of a spur, and FIG. 12 is a figure which shows the other example of a conveyance part. Members having the same functions and structures as those described in the first embodiment are designated by the same reference numerals.

A color image is formed in the same manner as the color image forming apparatus described in the first embodiment, but a conveying section 150 is provided between the toner image receiving body 14a and the fixing device 17 as fixing means. The recording paper P as a transfer material is conveyed to the fixing device 17 from the toner image receiving body 14a.

The transport unit 150 includes a box 151 and a box 151.
And a plurality of spurs 152 attached to the box 151 and a wire 153 stretched over the box 151. Box 151
A square hole 151a and grooves 151b and 151c are provided at both ends of the square hole 151a in an upper surface portion 151d of the shaft 15, and a spur 152 provided at the center of the spur 152 in the square hole 151a.
2a are dropped into the grooves 151b and 151c at both ends of the square hole 151a, and the spur 152 is rotatably attached to the box 151. As shown in FIGS. 8 and 9, the wire 153 is stretched over the box 151 by using the pin 154. At this time, the wire 153 as the guide member of the spur 152 is moved by the convex portions 151e and 151f of the box 151. It is stretched above the support shaft 152a at the center of rotation.

As shown in FIG. 10, the spur 152 preferably has a thickness of 0.05 to 0.5 mm and an outer diameter of 5 to 25 mm. For example, a 0.2 mm thick metal plate such as a stainless plate or a copper plate. Etching process, the protruding part 1 with sharp tip
It is composed of a hexagonal plate-shaped member having an outer diameter of 10 mm provided with 52b. This metal plate is grounded via a resistor of 10 ¹⁰ to 10 ¹⁴ Ω.

Further, as shown in FIG. 11, a support shaft 252a is attached to a hexagonal spur 252 having an abacus bead-shaped cross section with an outer diameter of 5 to 25 mm and made of a resin material and having a sharp tip 252b. Those provided with can also be used. Further, the shape of the spur protrusion is not limited to a hexagon, and a shape having a plurality of protrusions such as pentagon, octagon, and decagon is used. This resin is 10 ¹⁰ -10 ¹³ Ω
Preferably grounded using a cm resistance member.
The spur 152 is grounded via a high resistance member or by using a high resistance member because the toner and the transfer material are charged, and the charge accumulation of the spur 152 and the toner adhesion due to the mirror image force are eliminated to remove the toner image. This is to prevent the disturbance of.

The recording paper P on which the toner image is transferred is conveyed by the conveying section 1.
50, the support shaft 15 at the center of rotation of the spur 152
The recording paper P is formed by the wire 153 stretched above
Of the toner is scooped up and the toner image is not rubbed.
2, the spur 152 is driven to rotate while the tip 152 b of the spur 152 contacts or pierces the recording paper P, and the recording paper P is conveyed to the fixing device 17. In addition, spur 15
The wire 153 as a guide member stretched above the support shaft 152a of the second rotation center prevents the trailing edge of the recording paper P from dropping and prevents the toner image from being rubbed. Even when the recording paper P having the toner image formed on the lower surface in the second mode, the third mode, or the fourth mode described in the first embodiment is conveyed, the toner image is conveyed without being rubbed.

FIG. 12 shows another example of the transport section. As the guide member of the transport section 250, the upper surface portion 251d of the box 251 is used.
Is provided above the support shaft 152a of the spur 152. The leading edge of the recording paper P is prevented from being scooped up and the trailing edge of the recording paper P is prevented from dropping, and the rubbing of the toner image is prevented.

Further, it is also possible to assist the floating of the recording paper P by letting an air flow indicated by an arrow flow from the lower surface to the recording paper P as a transfer material through the square holes 251a of the box 251.

Embodiment 3 In the color image forming apparatus described in Embodiment 1,
In the present embodiment, the toner image receiving body is arranged above the image carrier. The third embodiment will be described with reference to FIG. FIG. 13 is a cross-sectional configuration diagram of a color image forming apparatus according to the third embodiment. Members having the same functions and structures as those described in the first embodiment are designated by the same reference numerals.

The photosensitive drum 10 as an image bearing member has, for example, a substrate formed of a transparent member such as glass or transparent acrylic resin as an inner side, a transparent conductive layer, an a-Si layer or an organic photosensitive layer (OPC). 13 is formed on the outer periphery of the substrate, and is rotated clockwise in the state of being grounded as shown by the arrow in FIG. A toner image receiver 14 a is provided on the photoconductor drum 10.

In the present embodiment, the exposure unit as the image exposure unit is arranged in accordance with the color order in which images are formed, as shown in FIG.
The Y and M exposure units 12 with respect to the rotation direction of the photosensitive drum 10 indicated by the arrow 3 indicate the right side of the photosensitive drum 10 (the vertical plane P passing through the central axis O of the photosensitive drum 10 in FIG. 13).
1-O-P2), and the C and K exposure units 12 are on the left side of the photoconductor drum 10 (left side of the vertical plane P1-O-P2 passing through the central axis O of the photoconductor drum 10 in FIG. 13).
And are arranged outside the photoconductor drum 10.

In the present embodiment, as the developing means provided in accordance with the color order in which images are formed, Y, M with respect to the rotation direction of the photosensitive drum 10 shown by the arrow in FIG.
13 is the right side of the photoconductor drum 10 (right side of the vertical plane P1-O-P2 passing through the central axis O of the photoconductor drum 10 of FIG. 13), and the C and K development units 13 are the photoconductor drums. 1
0 (the left side of the vertical plane P1-O-P2 passing through the central axis O of the photosensitive drum 10 in FIG. 13) outside the photosensitive drum 10, and the developing casings of the Y and M developing devices 13 respectively. A Y and M scorotron charger 1 above 138
1 is also the developing casing 13 of the C, K developing device 13.
A C and K scorotron charger 11 is disposed below the unit 8.

By the toner image forming means in the first to fourth modes described in the first embodiment, the toner image receiving body 14a (second image bearing) on the photosensitive drum 10 (first image bearing means) is obtained. Means) to form a color toner image.

The recording paper P, which is a transfer material, is fed from a paper feed cassette, which is a transfer material storage means (not shown), and is conveyed to the timing roller 15c.

The recording paper P is driven by the timing roller 15c so that the photosensitive drum 10 operates in the first to third modes.
The driving roller 14d and the driven roller 1 are synchronized with the color toner image carried on the toner image receiving body 14a and the toner image receiving body 14a.
The toner image receiving body 14a, which is stretched between 4e, is disposed above the photoconductor drum 10 and is provided close to or in contact with the photoconductor drum 10, and is conveyed to the transfer area 14b. At this time, the recording paper P is charged to the same polarity as the toner by the paper charger 14f, adsorbed to the toner image receiving body 14a, and fed to the transfer area 14b. By charging the paper with the same polarity as the toner, it is possible to prevent the toner image on the toner image receiver and the toner image on the image carrier from being attracted to each other.
Distortion of the toner image is prevented.

The color toner images carried on the photoconductor drum 10 are collectively transferred onto the recording paper P by the transfer device 14c to which a voltage having a polarity opposite to the toner (plus polarity in this embodiment) is applied ( First transfer means). In the case of the second and third modes, the backside toner carried on the peripheral surface of the toner image receiving body 14a by the backside transfer device 14g to which a voltage having the opposite polarity (plus polarity in this embodiment) to the toner is applied. The images are collectively transferred to the lower surface side of the recording paper P (second transfer means). At the time of transfer by the transfer device 14c, uniform exposure is performed by a simultaneous transfer exposure device 12d using, for example, a light emitting diode, provided inside the photosensitive drum 10 so as to perform good transfer so as to face the transfer device 14c. Is performed.

The toner image receiver 14a has a thickness of 0.5-2.
An endless rubber belt of 0 mm, a semiconductive substrate of silicon rubber or urethane rubber having a resistance value of 10 ⁸ to 10 ¹² Ω · cm, and a thickness of 5 μm to 50 μm as a toner filming prevention layer outside the rubber substrate. And a two-layer structure with fluorine coating. This layer also preferably has a similar semiconductivity. 0.1-thick instead of rubber belt base
0.5mm semiconductive polyester or polystyrene,
Polyethylene, polyethylene terephthalate and the like can also be used.

The toner remaining on the peripheral surface of the photoconductor drum 10 after the transfer is subjected to static elimination by the image carrier AC static eliminator 16 and then goes to the cleaning device 19 or the photoconductor drum 10
Cleaning blade 19a made of a rubber material abutting against
In order to eliminate the history of the photoconductor until the previous print, the peripheral surface of the photoconductor is erased by exposure by the uniform exposure device 12c before charging using a light emitting diode, and the charge at the time of previous printing Are removed and the next color image formation is started.

The recording paper P on which the color toner image is formed is
In order to prevent the toner image transferred to the recording paper P from the surface of the photoconductor drum 10 from being rubbed off, the charge is removed by the paper separation AC charge eliminator 14h for separating the transfer material and separated from the toner image receiver 14a. Through the conveyance unit 150 provided with the spur 152 described in the embodiment, it is conveyed to the fixing device 17 as a fixing unit composed of two rollers having a heater inside both rollers. Fixing roller 17a
By applying heat and pressure between the pressure roller 17b and the pressing roller 17b, the adhered toner on the front and back of the recording paper P is fixed,
The recording paper P on which an image has been recorded is sent by the paper discharge roller 18 and discharged to a tray outside the apparatus. As the discharging method, the front and back are reversed according to each mode, but each discharging method described in FIGS. 3 to 5 is adopted. Further, the transport unit 150 does not necessarily have to be provided.

The toner remaining on the peripheral surface of the toner image receiver 14a after the transfer is the toner image receiver cleaning device 14i.
Cleaning. The toner remaining on the peripheral surface of the photosensitive drum 10 after the transfer is transferred to the image carrier AC static eliminator 1.
After having been subjected to static elimination by 6, the toner is scraped into the cleaning device 19 by the cleaning blade 19a made of a rubber material that is in contact with the photosensitive drum 10, and is collected in a toner discharge container (not shown).
The photoconductor drum 10 from which the residual toner has been removed by the cleaning device 19 is uniformly charged by the Y scorotron charger 11, and enters the next image forming cycle.

Embodiment 4 An image forming process and each mechanism of a fourth embodiment of the image forming apparatus of the present invention will be described with reference to FIGS. 14 to 16. FIG. 14 is a sectional configuration diagram of a color image forming apparatus of a fourth embodiment of the image forming apparatus of the present invention, and FIG.
FIG. 16 is a circuit block diagram showing selection of various modes in the color image forming apparatus of the fourth embodiment, and FIG. 16 is a diagram showing a double-sided image forming state relating to the third mode and the fourth mode of the fourth embodiment. 16A is a diagram showing an example of double-sided image formation according to the fourth embodiment, and FIG.
FIG. 6B is a diagram showing another example of double-sided image formation according to the fourth embodiment. Members having the same functions and structures as those in the first embodiment are designated by the same reference numerals.

As shown in FIG. 15, the first to fourth modes of the image forming method of the color image forming apparatus of this embodiment are selected. Corresponds to the first mode stored in the ROM through the control unit by specifying an external signal indicating the transfer order of image data or specifying the page output order from the operation unit of the main body of the device or mode selection such as face-down / face-up discharge Program P11, program P12 corresponding to the second mode, program P13 corresponding to the third mode, fourth
One mode selected from the program P14 corresponding to the mode is called into the RAM, and the process control and execution of the color image forming apparatus are performed.

A color image forming method in the third mode will be described.

The toner image receiving body 14a stretched between the driving roller 14d and the driven roller 14e is
13 is rotated in the direction shown by the dotted line arrow a in FIG. 13 and the following image formation is performed in a state of being separated from the photosensitive drum 10.

The photosensitive drum 10, which is an image forming body, has a cylindrical substrate provided inside and a photosensitive layer such as a conductive layer, an a-Si layer or an organic photosensitive layer (OPC) formed on the outer periphery of the substrate. Yes, it is rotated in the clockwise direction indicated by the arrow in FIG.

The photosensitive drum 10 as an image forming body is driven and rotated, and in order to eliminate the history of the photosensitive drum 10 up to the previous printing, the uniform exposure device 1 as a charge eliminating means before charging.
21a, for example, a light-emitting diode is used to uniformly expose the peripheral surface of the photoconductor to remove the charge from the previous printing.

Scorotron charger 11 as charging means
Performs a charging action (in this embodiment, negative charging) on the above-described organic photoconductor layer of the photoconductor drum 10 by the control grid held at a predetermined potential and the corona discharge by the discharge electrode 11a. A uniform electric potential is applied to.

The photosensitive drum 10 is a scorotron charger 1.
After being uniformly charged to the peripheral surface by 1, an exposure unit 121 as an image exposure unit performs image exposure based on an image signal, and a latent image is formed on the photosensitive drum 10.

An exposure unit 121 as an image exposure means is a semiconductor laser as a light emitting element (not shown), and a rotary polygon mirror 12 for rotationally scanning a laser beam emitted from the semiconductor laser.
1b, an fθ lens 121c, a reflection mirror 121d, and the like, and a laser beam emitted from a semiconductor laser (not shown) is rotationally scanned by the rotary polygon mirror 121b, and rotates via the fθ lens 121c, the reflection mirror 121d, and the like. Image exposure is performed based on an image signal in the main scanning direction of the drum 10, and a latent image is formed on the photoconductor drum 10.

The peripheral portion of the photosensitive drum 10 is a developing means in which a developer composed of toner such as yellow (Y), magenta (M), cyan (C), black (K) and a carrier is filled. The developing device 13 for each color is provided, and first, development of the first color (for example, yellow) is performed by the developing sleeve 131.

The developing device 13 uses the non-contact developing method by applying a developing bias voltage to the electrostatic latent image formed on the photosensitive drum 10 formed by the charging by the scorotron charger 11 and the image exposure by the exposure unit 121. In a non-contact state, development is performed by reversal development with toner having the same polarity as the charging polarity (in this embodiment, the photosensitive drum is negatively charged, toner having a negative polarity).

The developing device 13 and the photosensitive drum 10 have a predetermined value, for example, 100 μm to 10 μm, by an abutting roller (not shown).
The developing sleeve 13 is maintained in a non-contact state with a gap of 00 μm, and during the developing operation by the developing device 13, a developing bias in which a direct current or an alternating current is applied to the developing sleeve 131 is applied, and the one-component or two-component developing accommodated in the developing device is applied. A jumper development with an agent is performed, and a DC bias having the same polarity (negative polarity in this embodiment) as that of the toner is applied to the negatively charged photosensitive drum 10 that grounds the transparent conductive layer to apply toner to the exposed portion. The non-contact reversal development is performed to attach the.

After the development of the first color is completed, the image process of the second color (for example, magenta) is started, and the photoconductor drum 10 is restarted.
Are uniformly charged by the scorotron charger 11, and a latent image based on the image data of the second color is formed by the exposure unit 121. At this time, the charge removal by the uniform exposure means 121a performed in the image forming process for the first color is not performed. Two
Development with the magenta developer of the color is the development sleeve 13
1 is performed. The development is performed by non-contact reversal development by applying an AC bias and a DC bias in a superimposed manner between the developing sleeve 131 and the photosensitive drum 10.

For the third color (cyan) and the fourth color (black), the same image forming process as the second color is performed, and four color toner images are superposed and developed on the photosensitive drum 10 (toner image). Forming means).

By the above image forming process, a superposed color toner image to be a back side image is formed on the photosensitive drum 10 (first image carrying means) as an image forming body.
The toner image receiving body 14a is rotated about the axis of the driving roller 14d in the direction shown by the dotted arrow b in FIG. 14, and is brought into contact with the photosensitive drum 10. At the fifth rotation of the photoconductor drum 10, the superimposed color toner image of the back side image on the photoconductor drum 10 is applied with a voltage having a polarity opposite to that of the toner (a positive polarity in this embodiment) in the transfer area 14b. The transfer device 14c collectively transfers the toner image on the toner image receiver 14a (second image carrier) provided in contact with the photosensitive drum 10. It is necessary to change the image data so that the front side image formed at this time is a mirror image of the back side image formation on the image carrier.

After the superimposed color toner images of the back side image on the photosensitive drum 10 are collectively transferred onto the toner image receiving body 14a, the toner image receiving body 14a is again centered on the axis of the driving roller 14d as shown in FIG. Is rotated in the direction indicated by the dotted arrow a, and is separated from the photoconductor drum 10.

The toner remaining on the peripheral surface of the photoconductor drum 10 after the transfer is discharged by the image forming body AC static eliminator 16 and then goes to the cleaning device 19 or the photoconductor drum 10.
Cleaning blade 19a made of a rubber material abutting against
In order to eliminate the history of the photoconductor until the previous printing, the peripheral surface of the photoconductor is erased by the exposure by the uniform exposure device 121a before the charging using a light emitting diode, for example, and the charge at the time of the previous printing is performed. Are removed and color image formation of the next surface image is subsequently performed.

In the same manner as the color image forming process described above, the surface image of the superimposed color toner image is formed on the photosensitive drum 10.

Next, the front surface image formed on the photosensitive drum 10 and the back surface image formed on the toner image receiving body 14a are synchronized in the transfer area 14b so that the toner image receiving body is formed. 14a is rotated about the axis of the drive roller 14d in the direction indicated by the dotted arrow b in FIG.
The photoconductor drum 10 is contacted.

The recording paper P which is the transfer material is sent out from the paper feed cassette 15 which is the transfer material storing means by the sending roller 15a, is fed by the feeding roller 15b and is conveyed to the timing roller 15c.

The recording paper P is driven by the timing roller 15c to drive the color toner image of the front surface image carried on the photosensitive drum 10, and the color toner image of the back surface image carried on the toner image receiving body 14a. Are synchronized and fed to the transfer area 14b. At this time, the recording paper P is charged to the same polarity as the toner by the paper charger 14f, adsorbed to the toner image receiving body 14a, and fed to the transfer area 14b. By charging the paper with the same polarity as that of the toner, it is possible to prevent the toner image on the toner image receiving body and the toner image on the image carrier from being attracted to each other, thereby preventing the toner image from being disturbed.

The surface images on the peripheral surface of the photosensitive drum 10 are collectively recorded on the recording paper P by the transfer device 14c to which a voltage having a polarity opposite to that of the toner (positive polarity in this embodiment) is applied.
(First transfer means). At this time, the back surface image on the peripheral surface of the toner image receiver 14a is not transferred to the recording paper P but exists on the toner image receiver 14a. next,
Polarity opposite to toner (positive polarity in this embodiment)
The transfer of the back surface image on the peripheral surface of the toner image receiving body 14a to the lower surface side of the recording paper P is collectively performed by the back surface transfer device 14g to which the above voltage is applied (second transfer means).

Since the toner images of the respective colors are overlapped with each other, it is preferable that the toners in the upper and lower layers of the toner layer are charged with the same charge amount and the same polarity in order to enable batch transfer. Therefore, in a double-sided image formation in which the polarity of the color toner image formed on the toner image receiving member 14a is inverted by corona charging or the polarity of the color toner image formed on the image carrier is inverted by corona charging, the lower layer is formed. The toner is not sufficiently charged to the same polarity, so that the transfer becomes unfavorable.

Repeated reversal development on the image carrier, the color toner images of the same polarity formed by superposition are collectively transferred to the toner image receiver 14a without changing the polarity, and then the recording paper without changing the polarity. The batch transfer to P is preferable because it contributes to the improvement of transferability in the back side image formation. Also for the surface image formation, reversal development is repeatedly performed on the image carrier, and the color toner images of the same polarity formed by superimposition are collectively transferred to the recording paper P without changing the polarity. It is preferable because it contributes to improvement of the property.

From the above, in color image formation, the first transfer means is operated to form a color toner image on the surface of the transfer material by using the above-mentioned front and back image forming methods, and then, A double-sided image forming method in which the second transfer unit is operated to form a color toner image on the back surface of the transfer material is preferably adopted.

The toner image receiver 14a has a thickness of 0.5-2.
An endless rubber belt of 0 mm, a semiconductive substrate of silicon rubber or urethane rubber having a resistance value of 10 ⁸ to 10 ¹² Ω · cm, and a thickness of 5 μm to 50 μm as a toner filming prevention layer outside the rubber substrate. And a two-layer structure with fluorine coating. This layer also preferably has a similar semiconductivity. 0.1-thick instead of rubber belt base
0.5mm semiconductive polyester or polystyrene,
Polyethylene, polyethylene terephthalate and the like can also be used.

The recording paper P on which the color toner images are formed on both sides is discharged by the paper separation AC charge eliminator 14h for separating the transfer material and separated from the toner image receiving body 14a, and both rollers have heaters. The sheet is conveyed to a fixing device 17 as a fixing device composed of two rollers. By applying heat and pressure between the fixing roller 17a and the pressure roller 17b, the toner adhered to the front and back of the recording paper P is fixed, and the recording paper P on which double-sided image recording has been performed is sent by the paper discharge roller 18. And discharged to a tray outside the apparatus.

The above is the image forming method in the third mode. As shown in FIG. 16A, when a large number of sheets, for example, n pages (n is an even number) are copied in the third mode. , The odd-numbered page color toner image formed on the photosensitive drum 10 and the even-page color toner image formed on the toner image receiving body 14a are double-sided images, and the nth page color toner image is faced down. Images are formed and ejected from the double-sided copies of pages n and n-1, and the first copy is on the top with the color toner image on the second page facing down and the toner image surface on the first page facing up. Is discharged.

The toner remaining on the peripheral surface of the toner image receiver 14a after transfer is the toner image receiver cleaning device 14i.
Cleaning. The toner remaining on the peripheral surface of the photosensitive drum 10 after the transfer is transferred to the image carrier AC static eliminator 1.
After being discharged by 6, the cleaning device 19 is scraped into the cleaning device 19 by the cleaning blade 19a made of a rubber material which is in contact with the photosensitive drum 10, and is collected by a screw 19b in a toner discharge container (not shown). To be done. The photoconductor drum 10 from which the residual toner has been removed by the cleaning device 19 is uniformly charged by the scorotron charger 11 and enters the next image forming cycle.

Similarly, in the image formation in the fourth mode, as shown in FIG. 16B, for example, when n pages (n is an even number) are copied, they are formed on the photosensitive drum 10. Even-numbered page color toner image and toner image receiver 1
The odd-numbered color toner images formed on 4a are used as double-sided images, and the first-page color toner images are turned down. Is discharged to the uppermost side with the color toner image on page n-1 down and the color toner image surface on page n up.

The toner image receiver 14a is again driven by the drive roller 1.
It rotates about the axis of 4d in the direction shown by the dotted arrow a in FIG. 14 and is separated from the photoconductor drum 10. The toner remaining on the peripheral surface of the toner image receiving body 14a after the transfer is cleaned by the blade of the toner image receiving body cleaning device 14i which is brought into contact with the toner image receiving body 14a. The toner remaining on the peripheral surface of the photoconductor drum 10 after transfer is made of a rubber material that is in the cleaning device 19 or is in contact with the photoconductor drum 10 after being discharged by the image forming body AC static eliminator 16. The cleaning blade 19a scrapes the cleaning device 19 to remove the screw 1
9b collects in a waste toner container (not shown). The photoconductor drum 10 from which the residual toner has been removed by the cleaning device 19 is uniformly charged by the scorotron charger 11 and enters the next image forming cycle.

The color images are formed in the third and fourth modes as described above, but the toner image forming means described above is used to form the photosensitive drum 10 as in the first embodiment.
The first mode in which the toner image carried on the (first image carrying means) is transferred onto the recording paper P, fixed and discharged, and the toner image on the photoconductor drum 10 is temporarily transferred to the toner image receiving body 14a.
(Toner image receiving member 1)
The second mode in which the toner image carried on the recording medium 4a is transferred onto the recording paper P, fixed, and discharged is performed in each of the above-described color image forming processes. In addition, as a discharge method,
According to each mode, the respective discharging methods similar to those described in the first embodiment with reference to FIGS. 3 to 5 are adopted. Further, the transport unit 150 provided with the spur 152 described in the second embodiment.
May be provided between the toner image receiver 14 a and the fixing device 17.

Fifth Embodiment An image forming process and each mechanism of a fifth embodiment of the image forming apparatus of the present invention will be described with reference to FIG.
FIG. 17 is a sectional configuration diagram of a color image forming apparatus according to the fifth embodiment of the image forming apparatus of the present invention. In this embodiment, the color toner image on the image carrier is formed by the same image forming process as in the first embodiment, and the color toner image on the image carrier is transferred to the toner image receiver or the intermediate image transfer member via the intermediate transfer member. The toner image is transferred to the transfer material, and therefore the arrangement of the toner image receiving body and the feeding direction of the transfer material are opposite to those in the first embodiment. Members having the same functions and structures as those in the first embodiment are designated by the same reference numerals.

A transfer belt 41 as an intermediate transfer member is provided so as to face the photosensitive drum 10 as an image carrier,
A first roller 42 as a transfer roller for pressing the intermediate transfer belt 41 against the photosensitive drum 10, a second roller 43 for pressing the intermediate transfer belt 41 against the toner image receiving body 14a in the transfer area 14b, and a backup roller 44, Stretched between. Reference numeral 45 is an intermediate transfer belt cleaning device.

In the same manner as described in the first embodiment, the scorotron charger 1 as the charging means for each color.
1. An overlapping color toner image is formed on the peripheral surface of the photosensitive drum 10 within one rotation of the photosensitive drum 10 by the exposure unit 12 as the image exposing unit and the developing device 13 as the developing unit (toner image formation). means).

The toner image forming means forms a superposed color toner image as a back side image on the photoconductor drum 10 as an image carrier, and the superposed color toner image of the back side image on the photoconductor drum 10 is transferred to the transfer roller. After being temporarily transferred to the intermediate transfer belt 41 (first image carrier) by 42, in the transfer area 14b, a transfer device 14c to which a voltage having a polarity opposite to the toner (positive polarity in the present embodiment) is applied, Drive roller 14d and driven roller 14e
The image is collectively transferred onto the toner image receiving body 14a (second image carrying means) which is stretched between and provided close to or in contact with the photosensitive drum 10.

Again, the surface image of the superimposed color toner image is formed on the photosensitive drum 10 by the toner image forming means and transferred to the intermediate transfer belt 41. It is necessary to change the image data so that the front side image formed at this time is a mirror image of the back side image formation on the image carrier.

A recording paper P as a transfer material is formed on the photoconductor drum 10, and once transferred to the intermediate transfer belt 41, the color toner image of the surface image carried on the intermediate transfer belt 41 and the toner image receiver. 14a is synchronized with the color toner image of the back side image carried on the transfer area 14a.
sent to b. At this time, the recording paper P is the paper charger 14f.
Is charged to the same polarity as the toner by the toner, and the toner image receiving body 1
It is adsorbed by 4a and fed to the transfer area 14b. By charging the paper with the same polarity as that of the toner, it is possible to prevent the toner image on the toner image receiving body and the toner image on the image carrier from being attracted to each other, thereby preventing the toner image from being disturbed.

The surface image on the peripheral surface of the intermediate transfer belt 41 is collectively transferred to the upper surface side of the recording paper P by the transfer device 14c to which the voltage of the opposite polarity (plus polarity in this embodiment) to the toner is applied. (First transfer means). On this occasion,
The rear surface image on the peripheral surface of the toner image receiving body 14a is not transferred to the recording paper P and exists on the toner image receiving body 14a. Next, the back surface image on the peripheral surface of the toner image receiving body 14a is collectively transferred to the lower surface side of the recording paper P by the back surface transfer device 14g to which a voltage having a polarity opposite to the toner (plus polarity in this embodiment) is applied. (Second transfer means).

The toner image receiver 14a has a thickness of 0.5-2.
An endless rubber belt of 0 mm, a semiconductive substrate of silicon rubber or urethane rubber having a resistance value of 10 ⁸ to 10 ¹² Ω · cm, and a thickness of 5 μm to 50 μm as a toner filming prevention layer outside the rubber substrate. And a two-layer structure with fluorine coating. This layer also preferably has a similar semiconductivity. 0.1-thick instead of rubber belt base
0.5mm semiconductive polyester or polystyrene,
Polyethylene, polyethylene terephthalate and the like can also be used.

The recording paper P on which color toner images are formed on both sides is neutralized by the paper separation AC neutralizer 14h for separating the transfer material and separated from the toner image receiving body 14a, and both rollers have heaters inside. The toner is conveyed to a fixing device 17 as a fixing unit composed of two rollers, and heat and pressure are applied to fix the adhered toner on the front and back of the recording paper P to perform double-sided image recording. Will be ejected to the tray.

Toner image receiver 1 after transfer in this embodiment
The toner remaining on the peripheral surface of 4a is a toner image receiver cleaning device 14 capable of contacting and releasing the toner image receiver 14a.
i blade cleans.

Also in the present embodiment, the selection of the first and second modes and the third and fourth modes described in the first and fourth embodiments is performed, and according to each mode, FIGS.
Also, the respective discharge methods similar to those described in Embodiment 4 with reference to FIG. 16 are adopted. Further, the transport unit 150 provided with the spur 152 described in the second embodiment may be provided between the toner image receiver 14 a and the fixing device 17.

Although the present invention has been described using the color image forming apparatus, it is needless to say that the present invention can be applied to a monochrome image forming apparatus. Further, the present invention includes not only the present method but also a modified example of forming a double-sided image.
Japanese Patent Application Laid-Open Nos. 63-180969 and 63-2, in which after inverting the polarity of the toner corresponding to the backside image shown in JP-A-28740, the toner is simultaneously transferred to both sides of the transfer material.
In the tandem method of JP-A-98255 and JP-A-1-44457, changing the process conditions and image data processing conditions between the front surface and the back surface as described above is used, and the image density and color tone are adjusted. And a double-sided image can be formed.

[0133]

According to the first aspect of the present invention, depending on the transfer order, output order, and discharge mode of image data, there is no need for a double-sided reverse paper feeding device that has been conventionally used, and page-aligned double-sided images are obtained. Can be output. Further, since the fixing device only needs to be passed through once, the transfer material is highly reliable to be conveyed. Especially, in the case of forming a color image, since the superimposed color toner images are collectively transferred, the color image on the toner image receiver Color misregistration, toner scattering, rubbing, and the like are less likely to occur, and good double-sided color image formation with little image deterioration is performed.

According to the second aspect, the toner image attached to the lower surface of the transfer material is conveyed without being rubbed.

According to the third aspect, the toner image adhering to the lower surface of the transfer material is more favorably conveyed without being rubbed.

According to the fourth aspect of the present invention, the transfer material is conveyed without scooping up the front end of the transfer material or dropping the rear end of the transfer material.

According to the fifth aspect, the toner image adhered to the lower surface of the transfer material is satisfactorily conveyed without being rubbed.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus according to a first embodiment of an image forming apparatus of the present invention.

FIG. 2 is a side sectional view of the image carrier of FIG. 1;

FIG. 3 is a diagram showing an image forming state in a first mode.

FIG. 4 is a diagram showing an image forming state in a second mode.

FIG. 5 is a diagram showing a double-sided image forming state relating to a third mode and a fourth mode.

FIG. 6 is a circuit block diagram showing various mode selections in the color image forming apparatus of the first embodiment.

FIG. 7 is a diagram showing another example of a discharging method.

FIG. 8 is a diagram illustrating an example of a transport unit.

FIG. 9 is a top view of the transport unit shown in FIG.

FIG. 10 is a perspective view of a spur.

FIG. 11 is a diagram showing another example of a spur.

FIG. 12 is a diagram showing another example of the transport unit.

FIG. 13 is a cross-sectional configuration diagram of a color image forming apparatus according to a third embodiment.

FIG. 14 is a cross-sectional configuration diagram of a color image forming apparatus according to a fourth embodiment of the image forming apparatus of the present invention.

FIG. 15 is a circuit block diagram showing various mode selections in the color image forming apparatus of the fourth embodiment.

FIG. 16 is a diagram showing a double-sided image forming state relating to a third mode and a fourth mode of the fourth embodiment.

FIG. 17 is a sectional configuration diagram of a color image forming apparatus according to a fifth embodiment of the image forming apparatus of the present invention.

[Explanation of symbols]

 10 Photoreceptor Drum 11 Scorotron Charger 12,121 Exposure Unit 13 Developing Device 14a Toner Image Receptor 14c Transfer Device 14g Back Transfer Device 17 Fixing Device 150,250 Conveyor 152,252 Spur 153 Wire P Recording Paper

Claims (5)

[Claims] 1. A toner image formed on an image carrier is directly transferred to a transfer material, while a toner image formed on the image carrier is once transferred to a toner image receiver and then transferred to a transfer material. In the image forming apparatus that transfers the toner image to both surfaces of the transfer material by the above, fixes and discharges the toner image, the toner image is formed on both surfaces of the transfer material according to the change of the transfer order or the output order of the image data or the change of the discharge mode. An image forming apparatus characterized by changing a page order. 2. An image forming apparatus having a conveying unit that conveys a toner image formed on an image bearing member onto a transfer material, and then conveys the toner image with its surface facing downward, in a conveying direction of the transfer material. The image forming apparatus is characterized in that a spur having a sharp tip is provided in the transport section. 3. The image forming apparatus according to claim 2, wherein the spurs are driven and rotated by a transfer material. 4. The image forming apparatus according to claim 2, wherein a linear guide member is stretched on a conveying portion along a conveying direction of the transfer material above a rotation center of the spur. apparatus. 5. The image forming apparatus according to claim 2, wherein an air flow is blown onto the transfer material from below the transfer material in the transport section.