JPH1097144A - Image forming device and method for image forming - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device and the method for the image forming capable of forming images on both sides of transferred body at high speed. SOLUTION: As for the image forming device, a digital coping machine 1 is provided with a photosensitive drum 8 and a transfer belt 16 held in roll contact with the photosensitive drum 8. In the case of performing both sides copying, the first toner image based on the image on a first surface of an original is formed on the photosensitive drum 8, the first toner image is temporarily transferred on the transfer belt 16, and the first toner image is charged in reverse polarity. Then, the image forming method is performed by forming the second toner image base on the image on the second surface of the original on the photosensitive 8, feeding a recording paper sheet P on a transferring position between the photosensitive drum 8 and the transfer belt 16, transferring the first toner image held on the transfer belt 16 to the rear side of the recording paper sheet P, and simultaneously transferring the second toner image formed on the photosensitive drum 8 to the surface of the recording paper P.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus and an image forming method for forming an image by transferring a developer image to a transfer material, and more particularly to an image forming method for forming an image on both surfaces of a transfer material. The present invention relates to an apparatus and an image forming method.

[0002]

2. Description of the Related Art Conventionally, apparatuses such as a copying machine, a printer, and a facsimile have been put into practical use as an image forming apparatus using an electrophotographic system. In this type of image forming apparatus, the surface of a drum-shaped or belt-shaped photoconductor as an image carrier is uniformly charged to a predetermined polarity by a corona charger or the like, and the photoconductor is charged to a predetermined polarity. An electrostatic latent image is formed by exposing the surface in accordance with an image signal, and the electrostatic latent image is developed and visualized by supplying a developer charged to a predetermined polarity on the surface of the photoreceptor. A recording sheet is supplied as a material to be transferred, and the visualized developer image is transferred onto the recording sheet by a corona charger or the like, and the developer image transferred onto the recording sheet is heated and fixed via a fixing unit. Thus, an image is formed on the recording paper.

In recent years, as copying machines, printers, and facsimile machines have been actively used in offices, the amount of recording paper used has been increasing. Therefore, apparatuses capable of forming images on both sides of recording paper have been put into practical use from the viewpoint of resource saving. Particularly, in a copying machine, double-sided copying is an essential function.

When an image is formed on both sides of a recording sheet by a copier, first, a developer image based on the image of the first page is formed on a photosensitive member, and the recording sheet is synchronized with the developer image. After the developer image is transferred to recording paper, the developer image is passed through a fixing device and fixed. Then, the recording paper on which the image of the first page is formed is inverted in the apparatus, and re-supplied to the photoconductor in synchronization with the developer image of the second page formed on the photoconductor. An image is formed on both sides of the recording sheet by transferring and fixing the developer image on the recording sheet.

[0005]

However, when an image is formed on both sides of a recording sheet as described above, more time is required for image formation than when an image is formed on only one side of the recording sheet. Become. That is, when forming the image of the second page on the back surface of the recording sheet, the recording sheet on which the image of the first page is fixed needs to be inverted while being circulated in the apparatus. , And the time required to form an image on only one side is three to four times as long. For example, in the case of a copier, the copy speed for single-sided copying of A4 size recording paper is 60 sheets / min, while the copying speed for double-sided copying is 15 sheets / min to 20 sheets / min.
There is a problem that the number of sheets / min is greatly reduced.

Further, as described above, at the time of duplex copying,
Since it is necessary to reverse the recording paper while circulating it in the apparatus, a large-scale mechanism for reversal is required,
There is a problem that the device becomes complicated and large.

An object of the present invention is to provide an image forming apparatus and an image forming method capable of forming an image on both sides of a transfer material at a high speed.

[0008]

In order to achieve the above object, an image forming apparatus according to a first aspect of the present invention sequentially prints first and second visible images based on an image of a document on an image carrier. An image forming means for forming, a holding member for temporarily holding the first visible image formed on the image carrier by the image forming means, and a holding member formed on the image carrier by the image forming means. Transfer means for transferring the first visible image to the holding member; supply means for supplying a material to be transferred to the surface of the holding member; and first means formed on the image carrier by the image forming means. After the visible image is transferred to the surface of the holding member by the transfer means, the transfer material is supplied onto the holding member by the supply means, and the first and second visible images are transferred by the transfer means. And a means for simultaneously transferring the image data to the material to be transferred.

According to the image forming apparatus of the present invention, a first electrostatic latent image is formed on an image carrier, and the first electrostatic latent image is charged to a first polarity. Image forming means for supplying a developer to the image carrier and forming a first developer image charged to a first polarity on the image carrier, and the image carrier carried by the first image forming means. And a first member for transferring the first developer image formed on the image carrier by the first image forming means to the holding member. Transfer means, charging means for charging the first developer image transferred to the holding member by the first transfer means to a second polarity opposite to the first polarity, and the first transfer means Means for forming a second electrostatic latent image on the image carrier on which the first developer image has been transferred, and applying the first electrostatic latent image to the second electrostatic latent image.
A second image forming means for supplying a developer charged to a first polarity to form a second developer image charged to a first polarity on the image carrier; Supply means for supplying the first transfer means, and the first transfer means, which is transferred to the holding member by the first transfer means and charged to the second polarity by the charging means,
Is transferred onto the first surface of the transfer material supplied by the supply means facing the holding member, and at the same time, the developer image formed on the image carrier by the second image forming means is transferred. And a second transfer means for transferring the second developer image charged to the first polarity to the second surface of the transfer material facing the image carrier.

According to the image forming apparatus of the present invention, after the first visible image formed on the image carrier is transferred to the holding member, the first visible image is charged to the opposite polarity, A second visible image is formed on the image carrier, a transfer material is supplied between the image carrier and the holding member, and a first developer image and a first developer image are formed on the first and second surfaces of the transfer material. The second developer image is simultaneously transferred.

Therefore, an image can be formed on both sides of the transfer material by feeding the transfer material only once between the image carrier and the holding member. Therefore, there is no need to reverse the transfer material on which the image has been formed on the first surface and supply it again for forming the image on the second surface, and the image forming speed when forming an image on both surfaces of the positive transfer material is reduced. Can be fast. Further, a complicated mechanism for reversing the transfer material is not required, and the apparatus can be downsized.

According to a third aspect of the present invention, an image forming apparatus forms a first electrostatic latent image on an image carrier, and the first electrostatic latent image is charged to a first polarity. Image forming means for supplying a developer to the image carrier and forming a first developer image charged to a first polarity on the image carrier, and the image carrier carried by the first image forming means. And a first member for transferring the first developer image formed on the image carrier by the first image forming means to the holding member. Transfer means, charging means for charging the first developer image transferred to the holding member by the first transfer means to a second polarity opposite to the first polarity, and the first transfer means Means for forming a second electrostatic latent image on the image carrier on which the first developer image has been transferred, and applying the first electrostatic latent image to the second electrostatic latent image.
A second image forming means for supplying a developer charged to a first polarity to form a second developer image charged to a first polarity on the image carrier; Supply means for supplying the first transfer means, and the first transfer means, which is transferred to the holding member by the first transfer means and charged to the second polarity by the charging means,
Is transferred onto the first surface of the transfer material supplied by the supply means facing the holding member, and at the same time, the developer image formed on the image carrier by the second image forming means is transferred. And a second transfer means for transferring the second developer image charged to the first polarity onto the second surface of the transfer material facing the image carrier, wherein the holding member is provided with the first transfer member. On the holding surface for holding the developer image, a cleaning member for removing the developer remaining on the holding surface is provided so as to be able to contact and separate from the holding surface.

Accordingly, when the first developer image transferred to the holding member and charged to the second polarity is supplied again to the transfer position, the first developer image transferred to the holding surface of the holding member is supplied. Is prevented from being separated by the cleaning member.

According to another aspect of the present invention, an image forming apparatus forms a first electrostatic latent image on an image carrier, and the first electrostatic latent image is charged to a first polarity. Image forming means for supplying a developer to the image carrier and forming a first developer image charged to a first polarity on the image carrier, and the image carrier carried by the first image forming means. And a first member for transferring the first developer image formed on the image carrier by the first image forming means to the holding member. Transfer means, charging means for charging the first developer image transferred to the holding member by the first transfer means to a second polarity opposite to the first polarity, and the first transfer means Means for forming a second electrostatic latent image on the image carrier on which the first developer image has been transferred, and applying the first electrostatic latent image to the second electrostatic latent image.
A second image forming means for supplying a developer charged to a first polarity to form a second developer image charged to a first polarity on the image carrier; Supply means for supplying the first transfer means, and the first transfer means, which is transferred to the holding member by the first transfer means and charged to the second polarity by the charging means,
Is transferred onto the first surface of the transfer material supplied by the supply means facing the holding member, and at the same time, the developer image formed on the image carrier by the second image forming means is transferred. And a second transfer means for transferring the second developer image charged to the first polarity to a second surface of the transfer material facing the image carrier, wherein the first transfer means is a first transfer means. The transfer is performed with one transfer output, and the second transfer unit performs transfer with a second transfer output different from the first transfer output.

According to a fifth aspect of the present invention, there is provided an image forming apparatus, comprising: reading means for reading an image of a document; processing the image read by the reading means; Image processing means for selectively outputting second image data of a mirror image of the image data, and a first visible image on the image carrier based on the first image data output by the image processing means. And an image forming means for forming a second visible image based on the second image data outputted by the image processing means; and an image forming means formed on the image carrier by the image forming means. A holding member for holding the first developer image; a transfer unit for transferring the first developer image formed on the image carrier by the image forming unit to the holding member; Supply means for supplying a transfer material, and the image forming means After transferring the first visible image formed on the image carrier to the surface of the holding member by the transfer means, the transfer means supplies the material to be transferred onto the holding member by the supply means. Means for simultaneously transferring the first and second visible images to the material to be transferred.

Further, according to the image forming method of the present invention, the first visible image is formed on the image carrier.
An image forming step, a first transfer step of transferring the first visible image formed on the image carrier in the first image forming step to a holding member, and a transfer of the first visible image A second image forming step of forming a second visible image on the formed image carrier, and supplying a transfer material between the image carrier and a holding member for carrying the first visible image And a first visible image transferred to the holding member in the first transfer step on the first surface of the transfer material supplied in the supply step facing the holding member. At the same time, a second transfer in which the transferable material transfers the second visible image formed on the image carrier in the second image forming step to the second surface facing the image carrier. And a process.

Further, according to the image forming method of the present invention, a first electrostatic latent image is formed on an image carrier, and the first electrostatic latent image is charged to a predetermined polarity. A first image forming step of forming a first visible image by supplying a developing agent to form a first visible image, and a holding member for holding the first visible image formed on the image carrier in the first image forming step A first transfer step of transferring the first visible image transferred onto the holding member in the first transfer step to a polarity opposite to the predetermined polarity; A second electrostatic latent image is formed on the image carrier to which the first visible image has been transferred in the first transfer step, and the second electrostatic latent image is charged with the developer having the predetermined polarity; Is supplied and developed to form a second visible image, and a second image forming step is performed in the second image forming step.
Supplying a material to be transferred between the image bearing member on which the visible image is formed and the holding member for carrying the first visible image; A second visible image transferred on the image carrier at the same time that the first visible image transferred in the first transfer step is re-transferred onto the material; And a transfer step.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a digital copying machine 1 (hereinafter, referred to as an image forming apparatus) as an image forming apparatus of the present invention.
1 shows a schematic configuration of the copier 1. The copying machine 1 includes a copying machine main body 10, and an automatic document feeder 100 that automatically conveys a document to a predetermined reading position and reverses the document as needed, on the upper portion of the copying machine main body 10.
(Hereinafter, simply referred to as ADF 100).

The ADF 100 is provided with a transport belt 102 that runs endlessly in both forward and reverse directions while being in contact with the upper surface of a transparent glass document table 10a disposed on the upper surface of the copying machine body 10. It also functions as a document press for bringing the document fed between the document table 10a and the document table 10a into close contact.

Below the ADF 100, that is, below the document table 10a, an image reading device 2 as reading means for optically reading an image of a document, and image information read by the image reading device 2 are converted into digital signals. An image processing device 4 as image processing means for processing and outputting the digitized image data as necessary, and a laser beam is applied to a photosensitive drum described later based on the image data output from the image processing device 4. A laser exposure device 6 that forms an electrostatic latent image on the photosensitive drum by irradiating the photosensitive drum is provided. Note that the image reading device 2, the image processing device 4, and the laser exposure device 6 are generally well known, and thus detailed description thereof is omitted here.

An image forming unit 20 having a photosensitive drum 8 as an image carrier is provided at a substantially central position of the copying machine main body 10. The photoconductor drum 8 is formed by coating an organic photoconductor 8b (see FIG. 2) on the surface of a cylindrical aluminum drum 8a, and is provided to be rotatable in the direction of arrow a in the figure.

Around the photosensitive drum 8, a scorotron charger 12 having a grid electrode for uniformly charging the surface of the photosensitive drum 8 to a negative polarity, and a laser beam emitted from a laser exposure device 6 according to image data. Exposure position 7, receiving device, developing device 14 for developing an electrostatic latent image by supplying a two-component developer in which toner and carrier charged to a negative polarity are mixed, and the same direction at the same speed as the peripheral speed of photosensitive drum 8 Endlessly, the photosensitive drum 8
The transfer belt 1 as a holding means for transferring the toner image (developer image) formed thereon onto a recording sheet P as a material to be transferred or temporarily holding the toner image without the recording sheet P
6. A drum cleaner 18 for collecting the residual toner remaining on the photosensitive drum 8 after transferring the toner image, and a discharge lamp 1 for removing the charge remaining on the photosensitive drum 8
Reference numerals 9 are sequentially arranged along the rotation direction of the photosensitive drum 8.

The transfer belt 16 has an electric resistance of 10 ¹⁰ Ω ·
cm, which is made of polycarbonate in which carbon is dispersed as a semiconductive material, and is wound around a driving roller 22 and a driven roller 24 disposed on both right and left sides of the copying machine body 10 below the photosensitive drum 8. It is turned and stretched. The length of the circumference of the transfer belt 16 is slightly longer than A3, which is the maximum paper size that can be used in the copying machine 1 of the present embodiment. The transfer belt 16 is provided with a white mark (not shown) for detecting the position of the transfer belt 16, and the position of the transfer belt 16 is always determined by an optical transfer belt position detection sensor (not shown). It can be detected.

At a transfer position where the photosensitive drum 8 and the transfer belt 16 are in contact with each other, a transfer roller 21 to which a positive bias voltage opposite to the charge polarity of the toner is applied is provided inside the transfer belt 16. I have. The transfer roller 21
It is formed of foamed urethane rubber in which carbon having an electric resistance of 10 ⁶ Ω · cm or less is dispersed, and is pressed with a predetermined pressure from the back side of the transfer belt 16 toward the photosensitive drum 8.
The transfer belt 16 is rotated following the travel of the transfer belt 16 in the direction of arrow b in the figure. Note that the transfer roller 21 and a power supply, which will be described later, function as a transfer unit of the present invention, and different voltages are applied to the transfer roller 21 according to the image forming mode.

In the vicinity of the transfer belt 16, a second
When the image forming mode (duplex mode) is selected,
A transfer belt charger 26 serving as a charging unit for charging the toner image of the first page of the document directly transferred to the transfer belt 16 to a positive polarity, which is a reverse polarity, and the transfer belt 16
A transfer belt cleaner 28 as a cleaning member provided to be able to contact and separate in the direction of arrow c in FIG. A backup roller 29 for generating a pressing force against the transfer belt cleaner 28 is provided inside the transfer belt 16 facing the transfer belt cleaner 28.

A cassette 3 containing recording papers P of three different sizes is provided below the copying machine body 10.
1, 32, 33 are provided, and pickup rollers 34, 35, 36 are provided in contact with the upper end of the uppermost recording sheet P accommodated in each cassette. Further, paper feed rollers 37 that convey the recording paper P taken out of the cassettes toward the respective conveyance rollers 38 are provided on the conveyance paths on the downstream side of the respective cassettes 31, 32, and 33. Further, the recording paper P fed via the respective transport rollers 38 is once aligned on the transport path on the front side of the transfer position where the photosensitive drum 8 and the transfer belt 16 are in contact with each other, and at a predetermined timing. A pair of registration rollers 39 for supplying to the transfer position are provided. In addition, these pickup rollers 34, 35, 36, paper feed roller 37, transport roller 3
8 and the registration roller 39 function as the supply means of the present invention.

On the left side of the transfer belt 16 in the figure, a fixing device 40 for fixing the toner image transferred onto the recording paper P to the recording paper P is provided. Downstream of the fixing device 40, a pair of paper discharge rollers 42 for conveying the recording paper P toward a paper discharge tray 44 protruding from the outside of the copying machine main body 10 are provided. The fixing device 40 has a pair of heat rollers 41 which are provided with heater lamps 41a and which are rotatably connected to each other, and simultaneously heat both surfaces of the recording paper P to a predetermined temperature to hold the recording paper P on both surfaces. The fused toner images can be fused and fixed at the same time.

Next, a description will be given of the operation when the image of the original is copied onto only one side of the recording paper P by the copying machine 1 having the above-described configuration. First, when a first image forming mode (single-sided mode) for copying an image of an original onto only one side of the recording paper P is selected and a copy button (not shown) is pressed, the original as an object to be read is placed in the ADF 100.
Is placed at a predetermined reading position on the document table 10a.

Then, the image of the document placed on the document table 10a is read by the image reading device 2, and the read image data is converted into a digital signal by the image processing device 4. Based on the digitized image data, a laser beam is applied to the exposure position 7 on the photosensitive drum 8 via the laser exposure device 6, and an electrostatic latent image based on the image of the original is formed on the photosensitive drum 8. It is formed. At this time, the photosensitive drum 8 is uniformly charged to −600 V by the scorotron charger 12 before the exposure position 7.

The electrostatic latent image formed on the photosensitive drum 8 is reversal-developed (developed on an exposed portion) by the developing device 14 to which a developing bias of -420 V is applied. A negative polarity toner image (developer image) corresponding to the image is formed.

On the other hand, the recording paper P stored in the cassettes 31, 32, 33 is picked up by pickup rollers 34, 35, 36.
, And is fed to a registration roller 39 via a paper feed roller 37 and a transport roller 38, where it is once aligned. Then, in synchronization with the toner image formed on the photosensitive drum 8, the recording paper P aligned by the registration roller 39 is sent to a transfer position between the photosensitive drum 8 and the transfer belt 16.

As shown in FIG. 2, when the toner image T on the photosensitive drum 8 and the recording paper P are sent to the transfer position in synchronization with each other, a voltage of plus 1200 V is applied to the transfer roller 21 by the transfer bias power supply 52. Then, a transfer electric field is formed from the transfer roller 21 to the photosensitive drum 8 via the transfer belt 16. Then, the toner image T on the photosensitive drum 8 is transferred to the recording paper P by the transfer electric field. still,
The transfer roller 21 includes a core 21a and an elastic member 21b provided on the outer periphery of the core 21a.

The recording paper P on which the toner image T has been transferred as described above is passed through the fixing device 40, where the toner image T is melted and fixed on the recording paper P. The recording paper P on which the toner image T is fixed is discharged out of the apparatus via a discharge roller 42, and is placed on a discharge tray 44.

Next, the operation for copying an image of a document on both sides of the recording paper P will be described. Here, the operation of copying the image of the first side of the original on the first side of the recording sheet P and copying the image of the second side of the original on the second side of the recording sheet P will be described as a representative. I do.

First, a second image forming mode (duplex mode) for copying images formed on both sides of a document to both sides of the recording paper P is selected, and when a copy button (not shown) is pressed, the image is read as an object to be read. Is placed at a predetermined reading position on the document table 10a by the ADF 100.
In this case, the document is arranged such that the first surface of the document faces the document table 10a.

Then, the image on the first surface of the document placed on the document table 10a is read by the image reading device 2, and the read image data is converted into a digital signal by the image processing device 4. Based on the digitized image data, a laser beam is applied to the exposure position 7 on the photosensitive drum 8 via the laser exposure device 6, and the laser beam is irradiated onto the photosensitive drum 8 based on the image of the first surface of the original. One electrostatic latent image is formed. In this case, the first electrostatic latent image on the photosensitive drum 8 is formed in a state where the image on the first surface is intact, that is, a normal image (first image data).

The first electrostatic latent image formed on the photosensitive drum 8 is developed by the developing device 14 to which a developing bias of -420 V is applied.
First of negative polarity (first polarity) corresponding to the surface image
(The first developer image) is formed.

As shown in FIG. 3, when the first toner image T1 formed on the photosensitive drum 8 is sent to the transfer position in a state where the recording paper P is not supplied to the transfer position, the transfer bias power supply 52 A voltage of +600 V is applied to the transfer roller 21 to form a transfer electric field from the transfer roller 21 to the photosensitive drum 8 via the transfer belt 16.
Then, the first electric field on the photosensitive drum 8 is
Is directly transferred onto the transfer belt 16.
In this state, the first toner image T1 formed on the transfer belt 16 has a mirror image relationship with the image of the document.

As shown in FIG. 4, the negative polarity first toner image T1 transferred onto the transfer belt 16 is passed through a transfer belt charger 26 as the transfer belt 16 travels. The transfer belt charger 26 includes a scorotron provided with a corona wire 26a and a case electrode 26b partly serving as a grid electrode, provided around the drive roller 22 around which the transfer belt 16 is wound. It is a charger. A voltage of +4.6 kV is applied to the corona wire -26a via the bias power supply 54, and a voltage of + 300V is applied to the case electrode 26b via the bias power supply 56. Therefore, the first belt held on the transfer belt 16
The toner image T1 is charged to a positive polarity (second polarity) by passing through the transfer belt charger 26.

The transfer belt cleaner 28 disposed around the transfer belt 16 operates in a state where the first toner image T1 is held on the transfer belt 16.
Has been evacuated to a position away from

On the other hand, the original on which the image on the first side has been read as described above is inverted by the ADF 100, and the image on the second side of the original is read by the image reading device 2. The image data of the second surface read by the image reading device 2 is
The image signal is converted into a digital signal by the image processing device 4 and output to the laser exposure device 6. The laser exposure device 6
The photosensitive drum 8 is irradiated with a laser beam based on the digital signal, and the second
Forming a second electrostatic latent image based on the surface image; In this case, the second electrostatic latent image on the photosensitive drum 8 is the second electrostatic latent image on the original.
An image of the surface is formed in a mirror image (second image data) relationship.

The second electrostatic latent image formed on the photosensitive drum 8 is developed by the developing device
Above the second negative polarity corresponding to the image of the second side of the original
(The second developer image) is formed. still,
The above-described series of image forming processes of the second toner image T2 includes:
The operation is performed in synchronization with the movement of the first toner image T1 held on the transfer belt 16, and the respective toner images T1 and T2 are simultaneously transported to the transfer position. At this time, the transfer belt 16
Is monitored by the operation of a transfer belt position detection sensor (not shown).

As shown in FIG. 5, the positive polarity first toner image T1 held on the transfer belt 16 and the negative polarity second toner image T2 formed on the photosensitive drum 8 are synchronized with each other. When the recording paper P is fed to the transfer position,
A voltage of plus 1600 V is applied to the transfer roller 21 by the transfer bias power supply 52. As a result, a transfer electric field from the transfer roller 21 to the photosensitive drum 8 via the transfer belt 16 is formed. Then, the first toner image T1 on the transfer belt 16 charged to the positive polarity is transferred to the first surface of the recording paper P, and at the same time, the second toner image T1 on the photosensitive drum 8 charged to the negative polarity is The image T2 is transferred to the second surface of the recording paper P.

Then, the recording paper P on which the first and second toner images T1 and T2 have been transferred to both sides is passed through a heat roller type fixing device 40, where the respective toner images T1 and T2 are transferred.
2 is melted and fixed on the first and second surfaces of the recording paper P, respectively. The recording paper P on which the toner images T1 and T2 are fixed is discharged out of the apparatus via a discharge roller 42,
It is placed on the paper output tray 44.

As described above, according to the copying machine 1 of the present embodiment, at the time of so-called double-sided copying in which images are formed on both sides of the recording paper P, the first image read from the original is temporarily placed on the transfer belt 16. The image is transferred to the recording paper P at the same time as the second image formed on the photosensitive drum 8. Therefore, the copy speed at the time of double-sided copying according to the present invention is about 1/2 times that at the time of single-sided copying, and the copying speed at the time of double-sided copying in a conventional copying machine is 1/3 to 1/4 times. The copying speed was greatly improved.

A transfer bias for transferring the first toner image T1 formed on the photosensitive drum 8 to the recording paper P;
A transfer bias for transferring the first toner image T1 formed on the photoconductor drum 8 to the transfer belt 16, a first toner image T1 formed on the transfer belt 16 and a second toner formed on the photoconductor drum The intensity of the transfer bias for simultaneously transferring the image T2 to both sides of the recording paper P is set to an appropriate intensity according to each transfer mode. Therefore, good transfer is always possible even in different transfer modes.

In the above-described embodiment, the mode in which the images on the first and second sides of the original are copied on the first and second sides of the recording paper P, respectively, has been described as an example. Any mode is effective as long as it is a mode for copying an image on both sides of the recording paper P.

In the above-described embodiment, the case where the semiconductive transfer belt is used has been described.
A transfer electric field may be formed by using an insulating transfer belt and charging the inside of the transfer belt with a corona charger at the transfer position.

Next, another embodiment of the present invention will be described. As shown in FIG. 6, in the present embodiment, the transfer drum 60 is
Was used. The transfer drum 60 is formed by coating the surface of a metal drum 60c with a conductive urethane rubber layer 60b of low hardness, and adding an ionic conductive material as a surface layer to 10 ¹⁰ Ω · cm.
A surface layer 60a made of a fluorine-based resin having a certain electric resistance is formed.

Around the transfer drum 60, a transfer drum charger 62 and a fur brush cleaner 64 are sequentially arranged along the rotation direction of the transfer drum 60. The transfer drum charger 62 and the fur brush cleaner 64 function in the same manner as the transfer belt charger 26 and the transfer belt cleaner 28 in the above-described embodiment, and the fur brush cleaner 64 is transferred by a moving mechanism (not shown). It is provided so as to be able to approach and separate from the drum 60. A transfer bias power supply 6 is provided on the metal drum 60c.
6, a predetermined transfer bias is applied.

Thus, the first toner image T1 formed on the photosensitive drum 8 is transferred onto the transfer drum 60, and the transferred first toner image T1 is charged to a positive polarity by the transfer drum charger 62. As a result, a second toner image T2 having a negative polarity is formed on the photosensitive drum 8, and the first and second toner images T1 and T2 are synchronized with the recording paper P and are transferred to the photosensitive drum 8 and the transfer drum 60. And a transfer bias is applied to the transfer drum 60 by the transfer bias power supply 66, so that the first and second toner images T1 and T2 are simultaneously transferred onto the recording paper P.

Therefore, also in the present embodiment, the copy speed at the time of double-sided copying is about 1/2 times that at the time of single-sided copying, and the copying speed at the time of double-sided copying in a conventional copying machine is 1/3 times. The copying speed was greatly improved as compared with the case of 1/4.

Next, an embodiment in which the present invention is applied to a color copying machine will be described. Note that the color copying machine of the present embodiment has substantially the same configuration as the copying machine 1 shown in FIG. 1 described above, and therefore, the same portions are denoted by the same reference numerals and description thereof will be omitted.

FIG. 7 shows four image forming units 20Y and 20Y corresponding to yellow, magenta, cyan and black.
1 shows a schematic configuration of a main part of a color copying machine having M, 20C, and 20B. Each image forming unit has substantially the same configuration as the image forming unit 20 of the above-described copying machine 1 shown in FIG. 1 except that developers of different colors are used, and operates in substantially the same manner as the image forming unit 20. Is done. Therefore, in each image forming unit, Y (yellow), M (magenta), C
(Cyan) and B (black).

Each of the image forming units 20Y, 20M, 20C,
A transfer belt 71 is provided below the transfer belt 20B.
The transfer belt 71 includes a driving roller 72 and a driven roller 7.
3 and run endlessly while being rolled and contacted with the photosensitive drums 8Y, 8M, 8C and 8B of each image forming unit. Further, inside the transfer belt 71, transfer rollers 21Y, 21M, 21C, 21B pressed toward the respective photosensitive drums 8Y, 8M, 8C, 8B are provided.

Around the transfer belt 71, the transfer belt 7
A transfer belt charger 74 and a transfer belt cleaner 75 for charging the first toner image T1 of each color held at 1 to a positive polarity are arranged. The transfer belt cleaner 75 is provided so as to be able to contact and separate from the transfer belt 71.

Thus, the recording paper P aligned by the pair of registration rollers 39 is sequentially fed to the respective transfer positions between the respective photosensitive drums and the transfer belt, and the recording paper P is selected according to each mode. A plurality of color toner images are superimposed and transferred on one or both surfaces of the recording paper P, and the recording paper P on which the toner images have been transferred passes through the fixing device 40 to be fixed and full-colored. The paper is discharged onto an external paper discharge tray 44.

In particular, when images are formed on both sides of the recording paper P, the first toner images T1 for each color corresponding to the images on the first side of the original are temporarily held on the transfer belt 71, and the first The toner image T1 is charged to the opposite polarity by the transfer belt charger 74 to form a second toner image T2 for each color corresponding to the image on the second surface of the document on the photosensitive drum of each color,
The recording paper P is supplied such that the first toner image T1 and the second toner image T2 coincide with each other on the front and back of the recording paper P, and the first and second toner images are transferred onto both sides of the recording paper P at four transfer positions. The two toner images T1 and T2 are simultaneously transferred.

In the color copying machine of this embodiment,
The copy speed at the time of double-sided copying was approximately half the speed at the time of single-sided copying, and the copying speed was greatly improved. As described above, according to the present invention, when forming images on both sides of the recording paper P, the first toner image T1 and the second toner image T2 are simultaneously transferred onto the recording paper P. The image can be transferred simultaneously to both sides of the recording paper P by two feedings, and it is not necessary to invert the recording paper P in the apparatus and feed it twice as in a conventional copying machine, so that the copying speed can be greatly increased. .

Further, since a large-scale mechanism for reversing the sheet, which is required in a conventional copying machine, is not required, simplification of the apparatus configuration, reduction in size, and reduction in cost can be achieved. Note that the present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the present invention.

[0061]

As described above, since the image forming apparatus of the present invention has the above-described configuration and operation, images on both sides of a document can be simultaneously transferred to both sides of a medium to be transferred. Makes copying faster.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a digital copying machine as an image forming apparatus of the present invention.

FIG. 2 is an operation explanatory diagram for explaining a one-sided copying operation in the copying machine of FIG. 1;

FIG. 3 is an operation explanatory diagram for explaining a two-sided copy operation in the copying machine of FIG. 1;

FIG. 4 is an operation explanatory diagram for explaining a two-sided copy operation in the copying machine of FIG. 1;

FIG. 5 is an operation explanatory diagram for explaining a two-sided copy operation in the copying machine of FIG. 1;

FIG. 6 is a schematic view showing another embodiment of the present invention.

FIG. 7 is a diagram schematically showing a configuration of a main part when the present invention is applied to a color copying machine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Digital copying machine, 2 ... Image reading device, 4 ... Image processing device, 6 ... Laser exposure device, 8 ... Photoreceptor drum, 10 ... Copier main body, 10a ... Origin plate, 12 ... Scorotron charger, 14 ... Development Device, 16: transfer belt, 18: drum cleaner, 19: static elimination lamp, 21: transfer roller, 22: drive roller, 24: driven roller, 26: transfer belt charger, 28: transfer belt cleaner, 29: backup roller, 31, 32, 33: Cassette, 34, 35, 36: Pickup roller, 37: Feeding roller, 38: Conveying roller, 39: Registration roller, 40: Fixing device, 41: Heat roller, 41a: Heater lamp, 42: Paper discharge rollers, 44: paper discharge tray, 100: ADF, 102: transport belt, P: recording paper.

Claims (7)

[Claims] An image forming means for sequentially forming a first and a second visible image based on an image of a document on an image carrier; and the first image formed on the image carrier by the image forming means. A holding member for temporarily holding a visible image; a transfer unit for transferring the first visible image formed on the image carrier by the image forming unit to the holding member; Supply means for supplying a material; transferring the first visible image formed on the image carrier by the image forming means to the surface of the holding member by the transfer means; Means for supplying a material to be transferred onto a member and simultaneously transferring the first and second visible images to the material to be transferred by the transfer means. 2. A first electrostatic latent image is formed on an image carrier, a developer charged to a first polarity is supplied to the first electrostatic latent image, and a first electrostatic latent image is supplied to the image carrier. First image forming means for forming a first developer image charged to a polarity of, and holding for holding the first developer image formed on the image carrier by the first image forming means. A member, first transfer means for transferring the first developer image formed on the image carrier by the first image forming means to the holding member, and holding by the first transfer means The first transferred to the member
Charging means for charging the first developer image to a second polarity opposite to the first polarity; and a second static image on the image carrier on which the first developer image has been transferred by the first transfer means. An electrostatic latent image is formed, a developer charged to a first polarity is supplied to the second electrostatic latent image, and a second developer image charged to a first polarity is applied to the image carrier. A second image forming means for forming; a supply means for supplying a material to be transferred to the surface of the holding member; a first transfer means for transferring the image to the holding member and charging the charging means to a second polarity; The obtained first developer image,
The transfer material supplied by the supply means is transferred to the first surface facing the holding member, and is simultaneously charged by the second image forming means to the first polarity formed on the image carrier. And a second transfer means for transferring the second developer image onto the second surface of the transfer material facing the image carrier. 3. A first electrostatic latent image is formed on an image carrier, a developer charged to a first polarity is supplied to the first electrostatic latent image, and a first electrostatic latent image is supplied to the image carrier. First image forming means for forming a first developer image charged to a polarity of, and holding for holding the first developer image formed on the image carrier by the first image forming means. A member, first transfer means for transferring the first developer image formed on the image carrier by the first image forming means to the holding member, and holding by the first transfer means The first transferred to the member
Charging means for charging the first developer image to a second polarity opposite to the first polarity; and a second static image on the image carrier on which the first developer image has been transferred by the first transfer means. An electrostatic latent image is formed, a developer charged to a first polarity is supplied to the second electrostatic latent image, and a second developer image charged to a first polarity is applied to the image carrier. A second image forming means for forming; a supply means for supplying a material to be transferred to the surface of the holding member; a first transfer means for transferring the image to the holding member and charging the charging means to a second polarity; The obtained first developer image,
The transfer material supplied by the supply means is transferred to the first surface facing the holding member, and is simultaneously charged by the second image forming means to the first polarity formed on the image carrier. And a second transfer means for transferring the second developer image to a second surface of the transfer material facing the image carrier, wherein the holding member holds the first developer image. An image forming apparatus, wherein a cleaning member for removing a developer remaining on the holding surface is disposed on the holding surface so as to be able to approach and separate from the holding surface. 4. A first electrostatic latent image is formed on an image carrier, a developer charged to a first polarity is supplied to the first electrostatic latent image, and a first electrostatic latent image is supplied to the image carrier. First image forming means for forming a first developer image charged to a polarity of, and holding for holding the first developer image formed on the image carrier by the first image forming means. A member, first transfer means for transferring the first developer image formed on the image carrier by the first image forming means to the holding member, and holding by the first transfer means The first transferred to the member
Charging means for charging the first developer image to a second polarity opposite to the first polarity; and a second static image on the image carrier on which the first developer image has been transferred by the first transfer means. An electrostatic latent image is formed, a developer charged to a first polarity is supplied to the second electrostatic latent image, and a second developer image charged to a first polarity is applied to the image carrier. A second image forming means for forming; a supply means for supplying a material to be transferred to the surface of the holding member; a first transfer means for transferring the image to the holding member and charging the charging means to a second polarity; The obtained first developer image,
The transfer material supplied by the supply means is transferred to the first surface facing the holding member, and is simultaneously charged by the second image forming means to the first polarity formed on the image carrier. And a second transfer means for transferring the second developer image to a second surface of the transfer material facing the image carrier, wherein the first transfer means transfers the first developer output with a first transfer output. Wherein the second transfer unit performs transfer with a second transfer output different from the first transfer output. 5. A reading means for reading an image of a document, processing the image read by the reading means, and selectively outputting first image data and second image data of a mirror image of the first image data. And a first visible image formed on the image carrier based on the first image data output by the image processing means, and output by the image processing means. An image forming unit that forms a second visible image based on second image data; a holding member that holds a first developer image formed on the image carrier by the image forming unit; Transfer means for transferring the first developer image formed on the image carrier by the image forming means to the holding member; supply means for supplying a material to be transferred to the surface of the holding member; The first visible image formed on the image carrier After transferring to the surface of the holding member by the transfer means, the transfer material is supplied onto the holding member by the supply means, and the first and second visible images are transferred by the transfer means to the transfer material. Means for simultaneously transferring images to the image forming apparatus. 6. A first image forming step of forming a first visible image on an image carrier, and a first visible image formed on the image carrier in the first image forming step. A first transfer step of transferring to a holding member, a second image forming step of forming a second visible image on the image carrier on which the first visible image has been transferred, A supply step of supplying a transfer material between the holding member that holds the first visible image, and the transfer material supplied in the supply step being the first surface on the first surface facing the holding member. At the same time as retransferring the first visible image transferred to the holding member in the transferring step,
The transfer material has the second surface on the second surface facing the image carrier.
A second transferring step of transferring the second visible image formed on the image carrier in the image forming step. 7. A first electrostatic latent image is formed on an image carrier, a developer charged to a predetermined polarity is supplied to the first electrostatic latent image, and development is performed. A first image forming step of forming an image, a first transferring step of transferring a first visible image formed on an image carrier in the first image forming step onto a holding member, A charging step of charging the first visible image transferred onto the holding member in the transfer step to a polarity opposite to the predetermined polarity; and transferring the first visible image in the first transfer step. Forming a second electrostatic latent image on the formed image carrier, supplying the second electrostatic latent image with the developer charged to the predetermined polarity, and developing the second electrostatic latent image; A second image forming step of forming a second visible image, an image carrier on which a second visible image is formed in the second image forming step, and a holding unit that carries the first visible image A supply step of supplying the transfer material, and a step of retransferring the first visible image transferred in the first transfer step onto the transfer material supplied in the supply step. A second transfer step of transferring a second visible image on the image carrier onto the transfer material at the same time.