JP2000019799A - Double-side image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent printing speed from being lowered in a marked degree even in the case of a rear face image by changing over to a mode of forming an image on a front face and using a reverse discharge means when rear face image is outputted. SOLUTION: When a reverse conveying part 40 is mounted and a face-up mode is selected, a control part calls a face-up program at the time of having reversing function from an ROM to form an image. When only a rear face image is judged by a front/rear judging means, front face image processing is performed by an image processing part on the rear face image to form a toner image of the rear face image on a photoreceptor drum 10, and the toner image of the rear face image is transferred to the front face of recording paper by a transfer apparatus 14c. The recording paper is fixed by a fixing device 20, reversed by a reverse conveying part 40 and discharged to a tray 41. There is therefore no need to retransfer transferred paper after transferring it once to an intermediate transfer body, so that printing speed is not lowered in a marked degree.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to copying in which a charging means, an image exposing means and a developing means are arranged around an image carrier to transfer and fix a toner image formed on the image carrier to both sides of a transfer material. The present invention relates to an electrophotographic double-sided image forming apparatus such as a printer.

[0002]

2. Description of the Related Art Conventionally, in double-sided copying, an image on one side formed on an image carrier is transferred and fixed on a transfer material, and this is temporarily stored in a two-sided reversing paper feeder, and the image bearing is again performed. A method has been adopted in which a transfer material is fed from a double-sided reversing sheet feeder in synchronization with an image formed on the body, and an image on the other surface is transferred and fixed onto the transfer material.

In this double-sided copying apparatus, as described above, the transfer of the transfer material, such as feeding to the two-sided reversing paper feeder and passing through the fixing device twice, is performed, so that the reliability of transfer of the transfer material is low. And wrinkles of the transfer material.
Further, as is well known, there is another problem that the copying material takes a lot of processing time because the transfer distance of the transfer material is long.

On the other hand, JP-B-49-37538, JP-B-54-28740, and JP-A-1-444.
No. 57, Japanese Patent Application Laid-Open No. 4-214576, and the like have proposed a device in which a toner image is formed on both surfaces of a transfer material and then fixed once.

[0005] The applicant of the present invention has disclosed Japanese Patent Application Laid-Open No. 9-258518.
By conducting technical disclosures such as No. 2, the research was conducted on a device that transfers toner images to both sides of the transfer material and simultaneously fixes the transfer material having the toner image on both sides, and has high reliability in transfer material transfer. It is possible to realize a double-sided image forming apparatus which does not cause jams and wrinkles and can significantly increase the processing speed of double-sided copying.

In the above-described double-sided image forming apparatus, the transfer material on which the toner images have been transferred on the front and back surfaces only needs to be passed through the fixing device once, so that the transfer material transfer reliability is high, and the transfer material transfer path is increased. The processing speed of copying can be shortened and shortened.

[0007]

In the above two-sided image forming apparatus, the first step of transferring the toner image formed on the image forming body to the surface of the transfer material, and the step of transferring the toner image formed on the image forming body, Is transferred to the back surface of the transfer material via the intermediate transfer material.
In forming a double-sided image, a back side image is first formed on an image forming body, and the toner image on the back side is temporarily transferred to an intermediate transfer material, and the front side image is formed on the image forming body. Is formed on the transfer material, first the toner image on the front surface is transferred to the front surface of the transfer material, then the toner image on the back surface on the intermediate transfer material is transferred to the back surface of the transfer material, and the toner images are formed on both surfaces of the transfer material. After formation, fixing is performed collectively.

When a single-sided image is formed by such a double-sided image forming apparatus, a surface image formed on an image forming body is directly transferred onto a transfer material in the case of a front side image. Although there is no difference from the one-sided copying machine,
In the case of the back side image, since the image is once transferred to the intermediate transfer body and then retransferred to the transfer material, there is a problem that the printing speed is significantly reduced. Such a problem cannot be overlooked in the case of a print having many back side images.

The present invention provides a double-sided image forming apparatus which does not significantly reduce the printing speed even in the case of a back side image.

[0010]

An object of the present invention is to provide a first step of transferring a toner image formed on an image forming body onto a first surface of a transfer material, and a step of transferring the toner image formed on the image forming body. A second step of transferring the toner image to the second surface of the transfer material via the intermediate transfer member. A reversing sheet discharging means and an image forming means, wherein when the reversing sheet discharging means has the output of the back side image, the mode is changed to a mode using image forming on the front side and using the reversing sheet discharging means. This is achieved by a double-sided image forming apparatus.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image forming apparatus according to the present invention will be described below.

According to the image forming apparatus of the present invention, a first step of transferring a toner image formed on an image forming body to a first surface (front surface) of a transfer material is intermediately performed. A double-sided image forming apparatus for forming a toner image on both sides of a recording sheet and performing fixing after forming a toner image on both sides of a recording sheet from a second step of transferring to a second side (back side) via a transfer body, wherein the first step and the second step Two embodiments of a double-sided image forming apparatus which forms a toner image on both sides of a recording sheet by two processes will be described.

First, a first embodiment will be described.
FIG. 1 is a diagram showing the overall configuration of hardware in a digital color image forming apparatus capable of forming double-sided images. The present invention is not limited to an image forming apparatus capable of forming a color image on both sides of a transfer material, but may be a monochrome digital copying machine capable of forming a double-sided image.

In FIG. 1, the color image forming apparatus includes an image reading section A, an image processing section B (not shown), and an image forming section C. B corresponds to an image processing unit, and the image forming unit C corresponds to an image forming unit.

The image reading section A is capable of reading images recorded on both sides of the document. In the image reading section A, the document 60 is stacked in page order from the lower side with the front side facing down. The lowermost document D is carried out toward the transport path 53 by the operation of the separating roller 52. The conveyance path 53 is provided with a sensor S1 for detecting the presence or absence of an image on the front surface / back surface of the document 60, and this information from the sensor S1 is input to the control unit B10. The conveyed original 60 is removed from the guide plate 61 urged to the position shown by the solid line, retracted to the position shown by the broken line, and fed onto the transparent platen glass 55 via the transport belt 54. Then, the document is temporarily stopped at the document reading position with the back face down.

An image of the back surface of the original 60 on the platen glass 55 is obtained from a first mirror unit 56 including an illumination lamp and a first mirror constituting a scanning optical system, and a second mirror and a third mirror positioned in a V-shape. The second mirror unit 57
Of the first mirror unit 56 at the speed V and the speed V / 2 in the same direction by the second mirror unit.
The image is read by the moving exposure, and is imaged on the light receiving surfaces of the image sensors CCD, which are three line sensors, through the projection lens 62 and the dichroic prism 63. The linear optical image formed on the image sensor CCD after color separation is photoelectrically converted into an electric signal (luminance signal) in sequence.

When the reading of the back side image is completed in the image reading section A, the original 60 is turned upside down through the reversing sheet feeding path 58 by the temporary reverse rotation of the conveying belt 54, and again passed through the conveying path 53. Through the platen glass 5
5, and is temporarily stopped at the document reading position with the front surface facing downward.

The surface image of the original 60 on the platen glass 55 is read by the above-described scanning optical system, color-separated, and photoelectrically converted into an electric signal by the image sensor CCD.

The original 60 whose image has been read on the platen glass 55 is stacked on the tray 64 via the discharge roller 59 by the operation of the transport belt 54 so that the surface of the original 60 faces downward from the lower side. The paper is ejected.

An image signal (image data) of the original image read by the image reading section A is transmitted to an image processing section B described later.
In, various image processing such as density conversion, filter processing, scaling processing, γ correction, and front / back image correction processing are performed, and then output to the image forming unit C.

The image forming section C is a laser printer using electrophotography, and forms an image on a recording sheet in accordance with an input image signal.

In the image forming section C, the photosensitive drum 10 as the first image carrier has a cylindrical base formed of a transparent member of, for example, optical glass or transparent acrylic resin provided inside, and a transparent conductive material. A photosensitive layer such as a layer, an a-Si layer, or an organic photosensitive layer (OPC) is formed on the outer periphery of the substrate, and is rotated clockwise as shown by an arrow in FIG. 1 in a grounded state.

As shown in the side sectional view of FIG. 2, the photosensitive drum 10 has a flange member 10a at both ends for engaging and fixing it.
And shaft 10b are fixedly mounted on the apparatus main body.
The gears G are integrally supported by the bearings 110a and 110b fitted in the flange members 10a and 10b at both ends, and are rotatably supported. As a result, it is rotated at a constant speed in a predetermined direction.

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 forming body. It is installed facing the body drum 10,
It has a control grid maintained at a predetermined potential with respect to the above-mentioned organic photosensitive layer of the photosensitive drum 10 and a discharge electrode 11a composed of, for example, a sawtooth electrode, and performs a charging action by corona discharge having the same polarity as the toner (this embodiment). In the embodiment, the photosensitive drum 10 is given a uniform potential. 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 located between the discharge electrode 11a of the scorotron charger 11 and the developing position of the developing unit 13. Be placed.

The exposure unit 12 is a linear exposure element in which a plurality of LEDs (light emitting diodes) as image exposure light emitting elements arranged in the main scanning direction in parallel with the axis 110 of the photosensitive drum 10 are arranged in an array. The exposure unit 12a and the SELFOC lens 12b as an equal-magnification imaging element are mounted on a holder (not shown). An exposure unit 12 for each color, a uniform exposure device 12
c and a transfer simultaneous exposure unit 12 d are mounted and housed inside the base body of the photosensitive drum 10. The image data read by the image reading unit A and subjected to image processing by the image processing unit B is input as an electric signal to the exposure unit 12 for each color.

As the exposure element, an element in which a plurality of light-emitting elements such as FL (fluorescent light emission), EL (electroluminescence), and PL (plasma discharge) are arranged in an array is used. The light emission wavelength of the light emitting element used in this embodiment is usually in the range of 780 to 900 nm, which is high in transmittance of the Y, M, and C toners when performing image exposure from the outside. Since the exposure method is used, a shorter wavelength of 400 to 780 nm, which does not sufficiently transmit light to the color toner, may be used.

A developing unit 13 provided in accordance with the color sequence in which an image is formed and a rotating photosensitive drum is provided in accordance with the color sequence.
In the present embodiment, the developing units 13 of Y and M are on the left side of the photosensitive drum 10 and the developing units 13 of C and K are on the right side of the photosensitive drum 10 with respect to the photosensitive drum 10 of FIG. And the developing casing 1 of the Y and M developing units 13
The scorotron chargers 11 for Y and M are disposed below 38, and the scorotron chargers 11 for C and K are disposed above the developing casing 138 of the C and K developing devices 13.

The developing device 13 as a developing means for each color includes
One-component or two-component developers of yellow (Y), magenta (M), cyan (C), and black (K) are accommodated, respectively, while maintaining a predetermined gap with respect to the peripheral surface of the photosensitive drum 10. At the developing position, for example, a thickness of 0.5 to 1 mm that rotates in the same direction as the rotation direction of the photosensitive drum 10,
The developing sleeve 131 is formed of a cylindrical non-magnetic stainless steel or aluminum material having an outer diameter of 15 to 25 mm.

The developing unit 13 is urged by an abutting roller (not shown) to a gap of a predetermined value from the photosensitive drum 10, for example, 100 to 1.
Developing device 1 for each color which is kept in
In the developing operation of the developing device 3, a developing bias to which a DC voltage or an AC voltage is further applied is applied to the developing sleeve 131, and a jumping development is performed by a one-component or two-component developer accommodated in the developing device, so that a negative charge is applied. A non-contact reversal development is performed in which a DC bias having the same polarity as the toner (in this embodiment, a negative polarity) is applied to the photosensitive drum 10 so that the toner adheres to the exposed portion.
The development interval accuracy at this time is 20 μm to prevent image unevenness.
Less than or equal to degree is required.

The developing unit 13 for each color described above converts the electrostatic latent image on the photosensitive drum 10 formed by the charging by the scorotron charger 11 and the image exposure by the exposure unit 12 into a non- In a non-contact state, the toner having the same polarity as the charged polarity (in the present embodiment, the photosensitive drum is negatively charged and the toner having a negative polarity) is reversely developed by a contact developing method.

When a photosensitive drum drive motor (not shown) is started by the start of image recording, a gear G provided on a rear flange member 10b of the photosensitive drum 10 is rotated through a driving gear to drive the photosensitive drum 10 as shown in FIG. The photosensitive drum 10 rotates in the clockwise direction indicated by the arrow, and at the same time, the charging action of the Y scorotron charger 11 disposed below the developing casing 138 of the yellow (Y) developing device 13 to the left of the photosensitive drum 10. Is started.

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

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, and a yellow (Y) toner image is formed as the photosensitive drum 10 rotates.

Next, the photosensitive drum 10 is placed on the yellow (Y) toner image, and further to the left of the photosensitive drum 10 and above the yellow (Y), a magenta (M) developing device 1 is provided.
An electric signal corresponding to the second color signal of the M exposure unit 12, that is, the M image data, is applied by the charging action of the magenta (M) scorotron charger 11 disposed below the third developing casing 138. Is performed, and magenta (M) is formed on the yellow (Y) toner image by non-contact reversal development by the M developing unit 13.
Are formed in a superimposed manner.

By the same process, the developing casing 13 of the developing unit 13 for cyan (C) is located on the right side of the photosensitive drum 10.
The cyan (C) toner image corresponding to the third color signal is further provided by a cyan (C) scorotron charger 11, an exposure unit 12 of C, and a 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 developing unit 13. A black (K) toner image corresponding to the signal is sequentially superimposed, and a color toner image is formed on the peripheral surface within one rotation of the photosensitive drum 10 (toner image forming means).

Exposure unit 1 for Y, M, C and K
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 image 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.

By the above-described image forming process, a superimposed color toner image serving as a back side image is formed on a photosensitive drum 10 (image forming body) as an image forming body. The transfer unit 14 to which a DC voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment) is applied to the toner image in the transfer area 14b.
c (first transfer means), which is stretched between the driving roller 14d and the driven roller 14e, and is a toner image receiving body 14a (second image carrying means) provided near or in contact with the photosensitive drum 10. On the intermediate transfer member). (FIG. 3A) At this time, for example, uniform exposure is performed by the transfer simultaneous exposure device 12d using an LED (light emitting diode) so that good transfer is performed.

The toner remaining on the peripheral surface of the photoreceptor drum 10 after the transfer is subjected to static elimination by the image forming body AC static eliminator 16 and then enters the cleaning device 19 or the photosensitive drum 10.
Cleaning blade 19a made of rubber material in contact with
In order to eliminate the history of the photoreceptor up to the previous print, the peripheral surface of the photoreceptor is removed by exposure by a uniform exposure unit 12c before charging using, for example, an LED (light emitting diode). Then, the next surface image is formed in a color image.

After the superimposed color toner image serving as the back side image is formed on the toner image receiving member 14a as described above, the superposed toner image serving as the front side image is continuously formed on the photosensitive drum 10. It is formed in the same manner as the image forming process (FIG. 3B). At this time, the back side image formed on the toner image receiver 14a and the front side image formed on the photosensitive drum 10 are synchronized in the transfer area 14b. The image data is changed by the image processing unit B described later so that the front surface image formed at this time is a mirror image of the back surface image formation on the photosensitive drum 10.

A paper feed cassette 15A in which recording paper P as a transfer material is stocked for each size as a transfer material storage means,
From 15B and 15C, the corresponding recording paper is sent out by the feeding roller 15a according to the instruction of the recording paper size,
The timing roller 1 is fed by the feeding roller 15b.
5c.

The recording paper P is driven by the timing roller 15c to form a front surface color toner image carried on the photosensitive drum 10 and a back surface color toner image carried on the toner image receiver 14a. Are fed to the transfer area 14b in synchronization with the above. At this time, the recording paper P is charged to the same polarity as the toner by a paper charger 14f as a transfer material charging means, is attracted to the toner image receiver 14a, and is fed to the transfer area 14b. By charging the paper with the same polarity as the toner, the recording paper P is prevented from attracting to the toner image on the toner image receiver 14a or the toner image on the photoconductor drum 10 outside the transfer portion, and the toner image is disturbed. Has been prevented. Further, as the transfer material charging means, the toner image receiving member 1 is used.
It is also possible to use a conductive roller, a brush charger or the like capable of abutting and releasing the abutment on 4a.

A surface image on the peripheral surface of the photosensitive drum 10 is collectively recorded on a recording paper by a transfer unit 14c as a first transfer unit to which a voltage having a polarity opposite to that of the toner (positive polarity in this embodiment) is applied. It is transferred to the upper surface side (front side) of P (first step). 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, a backside image on the peripheral surface of the toner image receiving body 14a is collectively recorded by a backside transfer unit 14g as a second transfer unit to which a voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment) is applied. The image is transferred to the lower surface side (back surface side) of the paper P (second step) (FIG. 3C). At the time of transfer by the transfer device 14c, a transfer simultaneous exposure device 12d using, for example, an LED (light emitting diode) provided inside the photosensitive drum 10 to face the transfer device 14c so that good transfer is performed. Uniform exposure is performed.

Since the toner images of the respective colors overlap each other, it is preferable that the toner in the upper layer and the toner in the lower layer of the toner layer are charged to the same polarity with the same charge amount in order to enable batch transfer. Accordingly, in the double-sided image formation in which the polarity of the color toner image formed on the toner image receiving body 14a is inverted by corona charging or the polarity of the color toner image formed on the photosensitive drum 10 is inverted by corona charging, Since the toner of the lower layer is not sufficiently charged to the same polarity, the transfer becomes unfavorable.

The reversal development is repeated on the photoreceptor drum 10, and the color toner images of the same polarity formed by superimposition are collectively transferred to the toner image receiver 14a without changing the polarity, and then recorded without changing the polarity. Batch transfer to paper P is preferable because it contributes to improving the transferability of backside image formation. Also for the surface image formation, reversal development is repeatedly performed on the photosensitive drum 10 to collectively transfer color toner images of the same polarity formed by superimposition onto the recording paper P without changing the polarity.
It is preferable because it contributes to improvement of the transferability of surface image formation.

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 ¹⁴ Ω · cm, and a thickness of 5 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. 0.1-0.5 thickness instead of rubber belt base
mm semiconductive polyester, polystyrene, polyethylene, polyethylene terephthalate, polyimide, or the like can also be used.

The recording paper P on which the color toner images are formed on both sides is used as a paper separating AC neutralizer 14h for separating the transfer material.
(Hereinafter also referred to as a separation pole), and is separated from the toner image receiving body 14a, and is transferred to a fixing device 30 as a fixing unit including two rollers having heaters inside both rollers, which will be described in detail later. Conveyed. By applying heat and pressure between the upper roller 310 and the lower roller 320, the adhered toner on the front and back sides of the recording paper P is fixed, and the recording paper P on which double-sided image recording has been performed can be attached and detached as described later. After passing through the reverse transport section 40, the recording paper P is sent by the paper discharge roller 18, and is discharged to the tray 41 outside the apparatus in a face-up mode with the front side image facing upward.

The toner remaining on the peripheral surface of the toner image receiver 14a after the transfer is provided in a toner image receiver cleaning device 14i as a cleaning means for the toner image receiver, and abuts on and contacts the toner image receiver 14a. It is cleaned by a blade that can be released. Further, the toner remaining on the peripheral surface of the photosensitive drum 10 after the transfer is subjected to static elimination by the image forming body AC static eliminator 16, and then enters a cleaning device 19 or is made of a rubber material which is in contact with the photosensitive drum 10. Cleaning device 1 by cleaning blade 19a
Then, the sheet is scraped into the sheet 9 and waits for the next image formation.

Next, the circuit configuration of the image processing section B will be described with reference to the block diagram of FIG.

In the image reading section A, an image pickup device CCD
The analog image signals of three colors separated by color output from
After being converted into a digital image signal by the / D converter B11, in image processing (I) B12, in addition to γ correction processing according to the characteristics of the image forming apparatus, extraction of the effective image area of the document, frame erasure and fold erasure The image data is stored in the memory B14.

Since a larger amount of image data is stored in the memory B14, the image data is compressed and stored by the image compression B13, and when read out from the memory B14, the image data is expanded and output by the image expansion B15. Has become.

The image processing section B performs image processing according to a command from the control section B10. The control unit B10 determines whether the image data output from the memory B14 is a front image or a back image when forming an image based on information from the front / back determining means B20. When the image data output from is the back side, image processing corresponding to the back side image is performed.

The operation panel of the image forming apparatus has selection buttons for selecting one-sided originals to two-sided images, two-sided originals to two-sided images, and the like. The front / back determination means B20 determines the front / back image of the image data decompressed from the memory. In the image forming apparatus of the present invention,
There is a face-up / face-down selection button to change the output mode, which will be described in detail later.

FIG. 5 shows details of the image processing (II) B16 and the data selector B19. The digital image signal for one page outputted from the memory B14 is subjected to the color processing B1.
In 61, color processing such as masking, inking, UCR, etc. is performed, and then in the γ conversion processing B162, different filter processing and γ correction are performed depending on whether the digital image signal is a front image or a back image. .

After the γ-conversion processing B162 is performed, the digital signals of each color of Y, M, C, and K that have been subjected to multi-value processing B163 such as screen angle, dither, and error diffusion are output to the data selector B19.

The data selector B19 includes a front side output memory B192A and a back side output memory B192B. When an image output instruction is issued from the control unit B10, the front side image data called from the memory B14 is read. Is processed by the image processing (II) B16, and is first processed by the selector (I) B191.
A, and then the image data of the back side is input to the back side output memory B192B. Backside output memory B19
When the image data is input to 2B, the image data is inverted by the selector (I) B191 so as to be a mirror image.

Then, the selector (II) B193 outputs the backside image data from the backside output memory B192B to the exposure unit 12 in accordance with the timing of the double-sided image formation in the image forming apparatus. Is formed. Then selector (II) B19
3, the surface image data from the surface output memory B 192A is output to the exposure unit 12, and the surface image is formed.

In the above description, the mirror image conversion processing of the image data is performed by the data selector B19. However, the circuit configuration may be performed by the gamma conversion processing B162.

In the double-sided image forming apparatus of the present invention, the fixing device 3
The recording paper P that has been fixed by 0 is discharged to the tray 41 outside the apparatus by the discharge roller 18 via the detachable reverse transport unit 40. As the reverse transport unit, a reverse transport unit 40A shown in FIG. 6 or a reverse transport unit 40B shown in FIG. 7 is used.

As shown in the explanatory view of FIG. 6, the reverse transport section 40A is provided with a T-shaped branch path 41A at right angles to the transport path as shown in the explanatory view of FIG. The paper P travels straight without being inverted, or is once conveyed toward the branch path and then inverted and is carried out with the upper surface being the lower surface. FIG. 6A shows a state when there is no reversal instruction from the control section B10. The branch path 41A is closed by the parallel guide plate 42A, and the recording paper P goes straight without reversing. Control unit B1
When there is a reversal instruction from 0, the reversal guide member 43A descends instead of retreating the parallel guide plate 42A, and FIG.
And the recording paper P descends on the branch path 41A by the reversing roller 44A. When the sensor S2A detects the trailing end of the lowered recording paper P, the reversing roller 44A rotates in the reverse direction, and the reversing guide member 43A also changes its posture as shown in FIG. Becomes In the reverse transport, the speed is greatly increased as compared with the transport speed during image formation.

A reverse transport section 40B as another reverse transport means
In the mounted state, as shown in the explanatory view of FIG.
Reversing roller 41B that rotates in both forward and reverse directions along the transport path
Is provided on the peripheral surface of the reversing roller 41B, and a grip 42B that can open and close to grip the leading end of the recording paper P is provided. In accordance with an instruction from the control unit B10, the reversing conveyance unit 40B advances the recording paper P straight without reversing, or rewinds once after being wound around the reversing roller 41B, and the upper surface is conveyed out as the lower surface. FIG. 7A shows a state in which there is no reversal instruction from the control unit B10. The reversing roller 41B is in a stopped state and the recording paper P
Goes straight without reversing. When a reversal instruction is given from the control unit B10, the grip 42 is opened as shown in FIG. 7A, and the sensor S2B detects the leading end of the recording paper P, and after a predetermined time, the grip 42 is opened. 7B, the reversing roller 41B rotates counterclockwise to
As shown in (b-1), the recording paper P is wound around the reversing roller 41B. After rotating by a predetermined amount, the reversing roller 41B reversely rotates along the reversing guide portion 43B with the rear end of the recording paper P as the leading end, and the grip 42
B is in an open state, and the recording paper P is reversely conveyed by the rollers 44B as shown in FIG. 7B-2. In the reverse transport, the speed is greatly increased as compared with the transport speed during image formation.

In the double-sided image forming apparatus of the present invention, the reversing and conveying unit 40 is detachable, and the operation panel of the apparatus has face-up (FU) / face-down (FD) selection means. The output form of the recording paper P is changed. FIG. 8 is a block diagram showing the control of the present embodiment. In addition to the circuit diagram shown in FIG. 4, a FU / FD selecting means B24 and a ROM (2) B25 for storing a face-up program and a face-down program as memories. And a reversing function presence / absence information B26 for detecting the attachment / detachment state of the reversing conveyance unit 40 and inputting the detected result to the control unit B10.

Hereinafter, the output mode instructs double-sided image formation (B
22) will be described.

(A-1) The face-up mode is selected (B26) because the reverse transport section 40 is not mounted (B26).
24) When the control is performed, the control unit B10 stores in the ROM (2) B25
To call up the face-up program when there is no inversion function to perform image formation.

That is, a first step of transferring the toner image of the first page (odd page) formed on the image forming body onto the surface of the recording paper P, and a second step (even number page) formed on the image forming body. And a second step of temporarily transferring the toner image of (Page) to the intermediate transfer member and transferring the toner image to the back surface of the recording paper P via the intermediate transfer member. In the second step, the toner image on the back surface is formed and fixed, and the toner image is discharged to the tray 40.

When the front / back determination means B20 determines that only the front side image is present, the image processing section B performs image processing corresponding to the front side to form a toner image on the front side on the photosensitive drum 10 and transfer it. After the toner image on the surface of the recording paper P is transferred to the surface of the recording paper P by the device 14c (first step), the recording paper P is fixed by the fixing device 30 and discharged to the tray 41.

When it is determined by the front / back determining means B20 that only the back side image is present, image processing corresponding to the back side is performed in the image processing section B to form a back side toner image on the photosensitive drum 10, and The toner image is temporarily transferred to the intermediate transfer member 14a by the transfer device 14c, and the toner image on the back surface of the intermediate transfer member 14a is transferred to the recording paper P by the back transfer device 14g.
(Second step), the image is fixed by the fixing device 30 and discharged to the tray 41.

(A-2) The face-down mode is selected (B26) because the reverse transport section 40 is not mounted (B26).
24), the control unit 10 calls up a face-down program without the inversion function from the ROM (2) B25 to form an image.

That is, the first step of transferring the toner image of the second page (even numbered page) formed on the image forming body onto the surface of the recording paper P, and the first step of forming the first page (odd numbered) on the image forming body And a second step of temporarily transferring the toner image of (Page) to the intermediate transfer member and transferring the toner image to the back surface of the recording paper P via the intermediate transfer member. In the second step, the toner image on the back surface is formed and fixed, and the toner image is discharged to the tray 41.

When the front / back determination means B20 determines that only the front image is formed, the image processing section B performs image processing corresponding to the back surface to form a toner image on the front surface on the photosensitive drum 10 and transfer the image. The toner image on the intermediate transfer member 14a is once transferred to the intermediate transfer member 14a by the device 14c, and the toner image on the front surface of the intermediate transfer member 14a is transferred to the back surface of the recording paper P by the back transfer member 14g (second step). The image is fixed and discharged to the tray 41.

When the front / back determination means B20 determines that only the back side image is present, the image processing section B performs image processing corresponding to the front side to form a back side toner image on the photosensitive drum 10, and Recording paper P by the transfer device 14c
After transferring the toner image on the back side to the front side (first step),
The image is fixed by the fixing device 30 and discharged to the tray 41.

(B-1) The reverse transport section 40 is mounted (B26), and the face-up mode is selected (B2
4) When this is done, the control unit B10 calls up the face-up program with the inversion function from the ROM (2) B25 to form an image. In this case, the use / non-use of the reversing sheet discharging function by the reversing conveyance unit 40 and the use mode in the image processing unit B have the following relationship in the present invention.

[0074]

[Table 1]

That is, when the image is determined to be a double-sided image by the front / back determining means B20, the first image formed on the image forming body is determined.
A first step of transferring the toner image of the page (odd page) to the surface of the recording paper P, and a transfer of the toner image of the second page (even page) formed on the image forming body to an intermediate transfer body once and intermediate transfer A second step of transferring the image to the back side of the recording paper P via the body, and forming a toner image on the front side in the first step and forming the toner image on the back side in the second step in the double-sided image formation, thereby fixing the image. Then, the reverse transport section 40 is discharged to the tray 41 without functioning.

When the front / back determination means B20 determines that only the front side image is formed, the image processing section B performs image processing corresponding to the front side to form a toner image on the front side on the photosensitive drum 10 and transfer it. After the toner image on the surface is transferred onto the surface of the recording paper P by the device 14c (first step), fixing is performed by the fixing device 30 and the reversing and conveying unit 40 is discharged to the tray 41 without functioning.

When the front / back determination means B20 determines that the image is a back side image, the back side image is subjected to front side image processing in the image processing section B to form a toner image of the back side image on the photosensitive drum 10 and transfer. After the toner image of the back surface image is transferred onto the front surface of the recording paper P by the device 14c (first step), fixing is performed by the fixing device 30, and the front and back are reversed by the reversing conveyance unit 40 on the discharge conveyance path to perform the tray 41. Is discharged.

(B-2) The reverse transport unit 40 is mounted (B26), and the face-down mode is selected (B2).
4) When the control is performed, the control unit B10 calls up the face-down program with the inversion function from the ROM (2) B25 to form an image. In this case, the use / non-use of the reversing sheet discharging function by the reversing conveyance unit 40 and the use mode in the image processing unit B have the following relationship in the present invention.

[0079]

[Table 2]

That is, when the image is determined to be a two-sided image by the front / back determination means B20, the first image formed on the image forming body is determined.
A first step of transferring the toner image of the page (odd page) to the surface of the recording paper P, and a transfer of the toner image of the second page (even page) formed on the image forming body to an intermediate transfer body once and intermediate transfer A second step of transferring the image to the back side of the recording paper P via the body, and forming a toner image on the front side in the first step and forming the toner image on the back side in the second step in the double-sided image formation, thereby fixing the image. Then, the reversing conveyance section 40 on the discharge conveyance path functions to reverse the front and back sides and is discharged to the tray 41.

When the front / back determination means B20 determines that only the front image is formed, the image processing section B performs image processing corresponding to the front surface to form a toner image on the front surface of the photosensitive drum 10 and transfer the image. After the toner image on the surface is transferred onto the surface of the recording paper P by the device 14c (first step), fixing is performed by the fixing device 30, and the reversing transport unit 40 on the discharge transport path functions to reverse the front and back. , Tray 41
Is discharged.

When the front / back determination means B20 determines that only the back side image is present, the image processing section B
To form a toner image for the back side image on the photosensitive drum 10 and transfer the toner image of the back side image to the front side of the recording paper P by the transfer unit 14c (first step). Fixing is performed by 30,
The recording paper P goes straight and is discharged to the tray 41 without functioning of the reversing conveyance section 40 on the discharge conveyance path.

As described in (B-1) and (B-2), in the present invention, image recording is performed only on one side of the recording paper P irrespective of the face-up mode or the face-down mode. In some cases, the toner image formed on the photosensitive drum 10 is transferred onto the recording paper P, and after the image is fixed, the reversing and conveying unit 40 functions as necessary, without using an intermediate transfer member. By performing image recording, the image processing speed can be significantly increased, and the processing time required for image formation can be greatly reduced.

In the double-sided image forming apparatus of the first embodiment shown in FIG. 1, when the reversing conveyance section 40 does not function, the recording paper P on which fixing has been completed goes straight and is discharged onto the tray 41. In the double-sided image forming apparatus according to the second embodiment shown in FIG. 9, when the reversing conveyance unit 40 does not function, the recording paper P after fixing is transported on the conveyance path until the recording paper P is discharged. The sheet is inverted and discharged onto the tray 41. Therefore, in the first embodiment and the second embodiment, the face-up mode and the face-down mode have an opposite relationship.

In the reversing conveyance section 40 used in the first and second embodiments described above, the front and back sides of the recording paper P are reversed, and the relationship between the leading and trailing ends is also reversed. Therefore, for the image to be reversed in the reverse transport section 40, the image processing section B
Such a problem is solved by calling the image data from the memory B14 from the rear end toward the head.

[0086]

According to the first aspect of the present invention, the printing speed at the time of forming the backside image, in which an image is formed only on the backside of the recording paper, is remarkably reduced, and the double-sided image formation with an improved print processing speed is achieved. A device has been provided.

According to the second and third aspects of the present invention, the printing speed is remarkably reduced in both the face-up mode and the face-down mode, and the printing processing speed is improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of a two-sided image forming apparatus according to a first embodiment.

FIG. 2 is a side sectional view of an image forming body.

FIG. 3 is an explanatory diagram showing a state of forming a toner image.

FIG. 4 is a block diagram showing a circuit configuration of double-sided image processing.

FIG. 5 is a block diagram showing a circuit configuration of an image processing unit and a data selector unit.

FIG. 6 is an explanatory diagram showing the operation of the reverse transport unit.

FIG. 7 is an explanatory view showing the operation of another reverse transport unit.

FIG. 8 is a block diagram illustrating control according to the present invention.

FIG. 9 is a cross-sectional configuration diagram of a two-sided image forming apparatus according to a second embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 photoconductor drum 11 scorotron charger 12 exposure unit (image exposure means) 13 developing device 14a toner image receiver (intermediate transfer member) 14c transfer device 14g backside transfer device 14h separation electrode 30 fixing device 40, 40A, 40B reversing conveyance section 41 tray A image reading unit B image processing unit B10 control unit C image forming unit

Continued on the front page (72) Inventor Kuki Nagase 2970 Ishikawacho, Hachioji-shi, Tokyo Konica Corporation F-term (reference) 2H027 FA13 FA30 FA35 FD08 2H028 BA06 BA09 BA16 BB02 BB04 2H072 AA32 AA36 AB14 CA05 FA01

Claims (3)

[Claims] A first step of transferring a toner image formed on the image forming member to a first surface of a transfer material; and a transfer material transferring the toner image formed on the image forming member via an intermediate transfer member. A two-stage image forming apparatus that forms a toner image on both surfaces of a transfer material and then performs fixing.
A reversible sheet discharging means for detachably fixing the transfer material and an image forming means are provided, and when the reversing sheet discharging means has the mode, the mode is changed to a mode using the image forming on the front side and the reversing sheet discharging means when outputting the back side image. A two-sided image forming apparatus. 2. A combination of one-sided and two-sided image formation and reversal sheet discharging means is changed by changing face-up sheet discharging or face-down sheet discharging.
2. The double-sided image forming apparatus according to 1. 3. The two-sided image forming apparatus according to claim 1, wherein the mode is prioritized when the reverse sheet discharging means is provided.