JP2002055585A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously toner images copy under the best processing condition by accommodating toner images by the amount of two pages on an intermediate transfer body, in an image forming device for forming the toner images formed on an image forming body on both sides of the transfer material through the intermediate transfer body. SOLUTION: This device has a 1st mode repeating a process for transferring the toner mage on the intermediate transfer body and a process for directly transferring the toner image to the transfer material for every two pages, and a 2nd mode repeating the processes for every page. Then the image is formed by appropriately switching two modes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for transferring a toner image formed on an image forming body to a transfer material by a toner image forming means.
More specifically, the present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile which obtains an image by fixing, and more specifically, forms a toner image on both surfaces of a transfer material via an intermediate transfer member and fixes the image to form a double-sided image. The present invention relates to an obtained image forming apparatus.

[0002]

2. Description of the Related Art In a conventional double-sided image forming apparatus, an image on one side formed on an image forming body is transferred onto a transfer material.
After fixing, the transfer material is temporarily stored in a two-sided reversal feeder, and then the transfer material is fed from the two-sided reversal feeder in synchronization with the image on the other surface to be formed on the image forming body. A method of transferring and fixing an image on the other surface is adopted.

In this double-sided image forming apparatus, the transfer material is conveyed such that the transfer material is once stored in a two-sided reversal feeding device and then fed again, so that the transfer distance of the transfer material is increased, and the double-sided image forming device is formed. However, there is a problem that it takes a lot of processing time. In addition, since the transfer material which has once passed through the fixing means and is easily curled is fed again, the reliability of transfer of the transfer material is low, which causes a jam or wrinkles of the transfer material.

On the other hand, JP-B-49-37538, JP-B-54-28740, and JP-A-1-444.
No. 57 and Japanese Unexamined Patent Publication No. 4-214576,
There has been proposed an image forming apparatus and an image forming method in which a toner image formed by an image forming body is transferred to both sides of a transfer material using an intermediate transfer body, and a double-sided image is obtained by one-time fixing.

[0005] In particular, JP-A-1-44457 and JP-A-4-214576 disclose an image forming body, a charging means,
A plurality of sets of image forming means including an image exposing means, a developing means, a cleaning means and the like are arranged in parallel in the order of yellow (Y), magenta (M), cyan (C) and black (K) on the intermediate transfer member, Methods have been proposed for forming a two-sided copy of an image.

[0006]

In an image forming apparatus which forms a color toner image on an image forming body and forms a color toner image on both sides of a transfer material via an intermediate transfer body, an image forming apparatus includes: A plurality of developing devices containing toners of Y, M, C, and K colors are provided on a peripheral portion, and in forming a color image,
By operating all the developing devices containing the toners of Y, M, C, and K colors to form a multi-color toner image on the image forming body in a superimposed manner, onto a transfer material or intermediate transfer Transfer is performed on a transfer material via a body. On the other hand, when forming a mono-color image, for example, one black color, only the developing device containing the K color toner is operated to form a black one-color toner image on the image carrier, and to form on a transfer material or an intermediate material. Transfer is performed on a transfer material via a transfer body.

The back side image formed on the image forming body is transferred onto the intermediate transfer body (primary transfer A). Next, the surface image formed on the image forming body is transferred onto the surface of the transfer material conveyed synchronously on the intermediate transfer body (primary transfer B). Further, with respect to the transfer material holding the front surface image on the front surface of the transfer material, the back image on the intermediate transfer body is transferred to the back surface of the transfer material by applying a transfer bias from above (secondary transfer). The transfer material holding the toner images on the front and back in this manner is attached and conveyed onto the intermediate transfer body, but the separation bias is applied for separation and elimination, and the transfer material is separated from the intermediate transfer body and conveyed to the fixing device. You. In the fixing device, a bias voltage is applied between fixing members (fixing rollers) that perform pinching and fixing, and fixing without toner disturbance is performed.

When reading or transferring an image during image formation, mistakes often occur at the beginning of the operation, and in particular, there are many document jams when reading a double-sided document. When feeding the transfer paper at the same time as the start of image reading or the start of image transfer in image formation, if an error occurs, stop the operation and stop the transfer of the transfer paper during the paper feeding. However, the transfer paper stopped in the middle of the paper feeding needs to be taken out from the transfer paper conveyance path as jam paper before the next operation, and the transfer paper is wasted. Further, removing jammed paper from the transport path not only takes time to remove, but also damages the surface of the photoreceptor, which is an image forming body, or damages the actuator of the sensor provided in the transport path.

On the other hand, if the feeding is started after the image reading is completed or after the image transfer is completed, the printing from the start of the image reading until the image is formed on the transfer paper and discharged is performed. The time is long and the image processing performance is not good.

A first object of the present invention is to form a toner image on both sides of a transfer material via an intermediate transfer member, and form a toner image on the intermediate transfer member.
For an image forming apparatus capable of storing toner images for pages, without increasing the processing time required for printing,
Further, even if an error occurs in image reading or image transfer, the transfer material is not wasted, and the jamming process does not have to be performed each time until the first print is discharged. It is an object of the present invention to provide an image forming apparatus that minimizes time.

When an image forming apparatus for forming a toner image on both surfaces of a transfer material via an intermediate transfer member uses a fixing device for fixing the transfer material by nipping and heating the transfer material with a heat roller, the transfer is performed when the transfer material is fixed. The heat is taken away by the material. A heater is provided inside the heat roller to supply the deprived heat.However, when a continuous copy is made and the transfer material passes continuously, the heat from the heat roller is supplied to the surface of the heat roller. Unable to catch up, the temperature of the heat roller surface drops below the initial fixing temperature. This phenomenon appears on the intermediate transfer member as 2
This is particularly likely to occur when a continuous copy is performed while storing toner images for pages. When the surface temperature of the heat roller falls below a predetermined fixing temperature due to continuous copying, the heat roller surface temperature returns to the predetermined fixing temperature. , Such as suspending the copying operation.

A second object of the present invention is to provide an image forming apparatus for forming a toner image on both sides of a transfer material via an intermediate transfer member capable of storing two pages of toner images, the heat roller being used for continuous copying. An object of the present invention is to provide an image forming apparatus in which a copy operation of a two-sided copy is continuously performed efficiently without stopping a copy operation based on a decrease in surface temperature.

[0013]

A first object of the present invention is to form a toner image on an image forming body based on image data input in page order, and to form the formed toner image via an intermediate transfer body or In an image forming apparatus in which toner images are directly transferred onto a transfer material and toner images are formed on both sides of the transfer material, image data of the first page is input when two pages of toner images can be stored on the intermediate transfer member. And forming a toner image based on the image data of the first page when it is determined that there is no image data of the third page, regardless of the input of the image data of the second page. Forming device.

The second object is to form a toner image on an image forming body based on image data input in page order,
In an image forming apparatus that transfers the formed toner image to the transfer material via an intermediate transfer member or directly to form images on both surfaces of the transfer material, two pages of toner images can be stored on the intermediate transfer member. The first mode in which the transfer of the toner image onto the intermediate transfer member and the direct transfer of the toner image on the transfer material are repeated every two pages, and the second mode is repeated every page. And an image forming apparatus.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to the description of the present invention, an embodiment common to image forming apparatuses to which the present invention is applied will be described. The present invention is not limited to the embodiments described below. The description in this section does not limit the technical scope of the claims and the meaning of terms. Also,
In the following description of the embodiment, when transferring a color toner image to a transfer material, the surface of the transfer material on the side facing the image forming body in the transfer area is the surface, and the other side of the transfer material, that is, the intermediate transfer The surface facing the body is called a back surface, an image transferred to the front surface of the transfer material is called a front image, and an image transferred to the back surface of the transfer material is called a back image.

An image forming process and each mechanism of the embodiment of the image forming apparatus of the present invention will be described with reference to FIGS. FIG. 1 is a sectional configuration view of a color image forming apparatus showing an embodiment of the present invention, FIG. 2 is a side sectional view of the image forming body of FIG. 1, and FIG. FIG. 4 is a diagram illustrating supply of a transfer material.

FIG. 1 is a diagram showing the entire hardware configuration of a digital color image forming apparatus capable of forming a double-sided image. The present invention enables a color image to be formed on both sides of a transfer material. The present invention is not limited to the image forming apparatus, and may be a black and white digital copying machine capable of forming double-sided images.

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

The image reading section A is capable of reading images recorded on both sides or one side (front side) of a document. In the image reading section A, the document 60 is stacked in page order from the upper side with the front side facing upward. The uppermost document 60 is carried out toward the transport path 53 by the operation of the carry-out roller 51 and the separating roller 52. 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 front surface facing downward.

The surface image of the original 60 on the platen glass 55 is obtained from a first mirror unit 56 comprising an illumination lamp and a first mirror constituting a scanning optical system, and a second mirror and a third mirror located 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 through the projection lens 62 on the light receiving surfaces of the image sensors CCD, which are three line sensors. 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 front image is completed in the image reading section A, the original 60 is turned upside down through the reversing paper feed path 58 by the temporary reverse rotation of the transport belt 54, and then again passed through the transport path 53. Through the platen glass 5
5, the document is temporarily stopped at the document reading position with the back surface facing downward.

The back side 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 conveyor 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 D.

The image forming section D forms an image on a recording sheet according to an input image signal by a laser printer using electrophotography.

In the image forming section D, 10 is a photosensitive drum as an image forming body, 11 is a scorotron charger as a charging unit for each color, 12 is an exposure unit as an image exposing unit for each color, and 13 is a unit for each color. A developing device which is a developing means of 14
a is an intermediate transfer member, 14c is a primary transfer device as a first transfer device, 14g is a secondary transfer device as a second transfer device, 15g
Reference numeral e denotes a timing roller as a transfer material supply unit, and reference numeral 17 denotes a fixing device as a fixing unit.

The photosensitive drum 10, which is an image forming body, has a transparent conductive layer, a-, on the outer periphery of a cylindrical base formed of, for example, a transparent member of optical glass or transparent acrylic resin.
A photosensitive layer such as an Si layer or an organic photosensitive layer (OPC) is formed, and is rotated clockwise as indicated by an arrow in FIG.

As shown in FIG. 2, the photosensitive drum 10 has flange members 10a and 10a at both ends for engaging and fixing it.
b is rotatably supported by bearings 110a and 110b fitted into flange members 10a and 10b at both ends with respect to a drum shaft 110 erected and fixed to the apparatus main body, and is rotatably supported. Is driven at a constant speed in a predetermined direction by being driven by meshing with a drive gear on the apparatus body side.

A scorotron charger 11, which is a charging unit for each color, an exposure unit 12, which is an image exposure unit for each color, and a developing unit 13, which is a developing unit for each color, constitute a set of these units, and are composed of yellow (Y), Four photoconductor drums 1 are provided for image forming processes of magenta (M), cyan (C), and black (K), and are indicated by arrows in FIG.
With respect to the 0 rotation direction, they are arranged in the order of Y, M, C, and K.

The scorotron charger 11, which is a charging unit for each color, is attached to the photosensitive drum 10 in a direction orthogonal to the moving direction of the photosensitive drum 10, and is attached to the photosensitive layer 10 of the photosensitive drum 10. Has a control grid maintained at a predetermined potential and a discharge electrode 11a composed of, for example, a sawtooth electrode, and is charged by corona discharge having the same polarity as the toner (in the present embodiment, negative charge).
To apply a uniform potential to the photosensitive drum 10.
Other wire electrodes can be used as the discharge electrode 11a.

Exposure unit 1 as image exposure means for each color
2 is arranged inside the photoconductor drum 10 such that the exposure position on the photoconductor drum 10 is located on the downstream side in the rotation direction of the photoconductor drum 10 with respect to the scorotron charger 11 for each color. The exposure unit 12 includes the photosensitive drum 1
A linear light-emitting element 12a in which a plurality of LEDs (light-emitting diodes) as light-emitting elements arranged in the main scanning direction in parallel to the 0 axis, and a selfoc lens 12b as an equal-magnification imaging element; And a holder (not shown) to which is attached. In addition to the exposure unit 12 for each color, a uniform exposure unit 12c and a simultaneous transfer exposure unit 12d are attached to the holding member 20, and are housed integrally inside the base body of the photosensitive drum 10. The image data read by the image reading unit A or the image data of each color stored in the memory is sequentially read and subjected to image processing, and then input to the exposure unit 12 for each color as an electric signal. Other FL (phosphor emission),
A device in which a plurality of light-emitting elements such as EL (electroluminescence) and PL (plasma discharge) are arranged in an array is used. The emission wavelength of the light-emitting element used in this embodiment is generally 68, which is highly transparent to Y, M, and C toners.
A wavelength in the range of 0 to 900 nm is preferable, but a shorter wavelength which does not have sufficient transparency for the color toner since image exposure is performed from the inside (back surface) of the photosensitive drum 10 may be used.

The developing device 13 as a developing means for each color includes
For example, a cylindrical non-magnetic stainless steel having a thickness of 0.5 to 1 mm and an outer diameter of 15 to 25 mm, which keeps a predetermined gap with respect to the peripheral surface of the photosensitive drum 10 and rotates in the forward direction with respect to the rotation direction of the photosensitive drum 10 or It has a developing sleeve 131 formed of an aluminum material and a developing casing 138, and contains therein a one-component or two-component developer of yellow (Y), magenta (M), cyan (C) and black (K). ing. Each of the developing devices 13 is provided with a predetermined gap, for example, 100 to 1000 μm, from the photosensitive drum 10 by an abutting roller (not shown).
m, and is kept in a non-contact state.
A non-contact reversal development is performed by applying a developing bias in which a DC voltage and an AC voltage having the same polarity as the toner (in this embodiment, a negative polarity) are superimposed, and a toner image is formed on the photosensitive drum 10. Form.

The intermediate transfer member 14a has a volume resistivity of 10 ⁸ -1.
It is an endless belt having a resistance of 0 ¹² Ω · cm and a surface resistivity of 10 ⁸ to 10 ¹² Ω / □, for example, a 0.5 to 2.0 mm thick anti-conductive rubber belt in which a conductive material is dispersed in silicon rubber or urethane rubber. This is a seamless belt having a two-layer structure in which a fluorine coating having a thickness of 5 to 50 μm is preferably formed on the outside of the substrate as a toner filming preventing layer. In addition to the above, a conductive material is dispersed in an engineering plastic such as a modified polyimide, a thermosetting polyimide, an ethylene tetrafluoroethylene copolymer, a polyvinylidene fluoride, or a nylon alloy. A 0 mm semiconductive film can also be used. The intermediate transfer member 14a is circumscribed by a driving roller 14d and a driven roller 14e, stretched by a tension roller 14k, and rotated in a counterclockwise direction indicated by an arrow in FIG.

A primary transfer device 14c as a first transfer means
Is provided to face the photosensitive drum 10 with the intermediate transfer member 14a interposed therebetween, and forms a transfer area 14b between the intermediate transfer member 14a and the photosensitive drum 10. The primary transfer unit 14c has a polarity opposite to that of the toner (positive polarity in this embodiment).
Is applied to form a transfer electric field in the transfer area 14b, thereby transferring the toner image on the photoconductor drum 10 onto the intermediate transfer body 14a or onto the surface of the recording paper P as a transfer material.

Secondary transfer unit 14g as second transfer means
Is provided so as to face a conductive driving roller 14d that is grounded with the intermediate transfer member 14a interposed therebetween, and a DC voltage having a polarity opposite to that of the toner (positive polarity in this embodiment) is applied to the intermediate transfer member 14a. Is transferred to the back surface of the recording paper P.

Timing roller 1 as transfer material supply means
5e feeds the recording paper P, which is a transfer material, to the transfer area 14b in synchronization with the color toner image of the front surface image on the photosensitive drum 10 or the color toner image of the back surface image on the intermediate transfer body 14a.

Paper separation AC neutralizer 1 as transfer material separating means
4h, which is preferably constituted by a corona discharger, is provided at an end of the intermediate transfer belt 14a on the side of the fixing device 17 so as to face a drive roller 14d which is grounded with the intermediate transfer belt 14a interposed therebetween, and is applied to a secondary transfer unit 14g. An AC voltage in which a DC voltage having the same polarity (positive polarity in the present embodiment) as the DC voltage is superimposed is applied, and the recording paper P conveyed by the intermediate transfer belt 14a is neutralized to remove the intermediate transfer belt 14a.
Separate from

A fixing device 17 serving as a fixing means includes a first fixing roller 17a having a heater therein and a second fixing roller 1a.
7b, which fixes the toner image on the recording paper P by applying heat and pressure between the first fixing roller 17a and the second fixing roller 17b.

Next, the image forming process will be described. When the image recording is started, in the image reading unit A,
The image data of the document image read by the image sensor or the image data of the image edited by the computer is converted to Y (yellow), M (magenta),
It is processed as an image signal for each color of C (cyan) and K (black).

A gear G provided on the rear side flange 10b of the photosensitive drum 10 is rotated through a driving gear (not shown) by the start of a photosensitive member driving motor (not shown) at the start of image recording, and the photosensitive drum 10 Is rotated clockwise as indicated by the arrow in FIG. 1, and at the same time, the application of a potential to the photosensitive drum 10 is started by the charging action of the scorotron charger 11 for yellow (Y).

After a potential is applied to the photosensitive drum 10, the first color signal, that is, Y
Exposure by an electric signal corresponding to the image data is started, and the rotation of the photosensitive drum 10 forms an electrostatic latent image corresponding to the Y image of the original image on the photosensitive layer on the surface.

The latent image is reversal-developed in a non-contact state by the Y developing unit 13 to form a yellow (Y) toner image in accordance with the rotation of the photosensitive drum 10.

Next, a potential is applied to the photosensitive drum 10 from above the yellow (Y) toner image by the charging action of the magenta (M) scorotron charger 11, and the second color signal of the M exposure unit 12 is applied. That is, exposure is performed by an electric signal corresponding to M image data, and the M developing device 13
Yellow (Y) by non-contact reversal development
A toner image of magenta (M) is formed on the toner image of FIG.

By the same process, a cyan (C) toner image corresponding to the third color signal is further formed by the cyan (C) scorotron charger 11, the exposure unit 12 of C and the developing unit 13 of C. Further, a black (K) toner image corresponding to the fourth color signal is sequentially superimposed and formed thereon by a black (K) scorotron charger 11, an exposure unit 12 of K, and a developing unit 13 of K. As a result, a color toner image is formed on the peripheral surface of the photosensitive drum 10 within one rotation.

These exposure units 1 for Y, M, C and K
Exposure of the photosensitive layer of the photosensitive drum 10 by 2 is performed from the inside of the photosensitive drum 10 through the aforementioned transparent substrate. Therefore, the exposure of the images corresponding to the second, third, and fourth color signals is performed without any influence from the previously formed toner image, and is equivalent to the image corresponding to the first color signal. 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 image is formed on the photosensitive drum 10 as an image forming body, and the superimposed color toner image of the back image on the photosensitive drum 10 is transferred. In the area 14b, the primary transfer unit 14c to which a DC voltage of 4 to 6 kV having the opposite polarity (positive polarity in the present embodiment) to the toner is applied is collectively transferred onto the intermediate transfer body 14a (primary transfer). Transcription A). At this time, the transfer simultaneous exposure device 1 using, for example, a light emitting diode is used so that good transfer is performed.
Uniform exposure by 2d is performed.

The toner remaining on the peripheral surface of the photosensitive drum 10 after the transfer is subjected to static elimination by the photosensitive drum AC static eliminator 16 and then reaches the cleaning device 19 where the photosensitive drum 1 is removed.
Cleaning blade 19 made of rubber material in contact with zero
In order to eliminate the history of the photoreceptor up to the previous printing, the peripheral surface of the photoreceptor is neutralized by, for example, exposure by a uniform exposure unit 12c before charging using a light emitting diode, and the previous printing is performed. After the charge is removed, the next color image is formed.

After the superimposed color toner image serving as the back side image is formed on the intermediate transfer body 14a as described above, the back side image on the intermediate transfer body 14a and the transfer area 1
4b, the superimposed color toner image serving as the surface image is formed on the photosensitive drum 10 in the same manner as in the above-described color image forming process. The image data of the front surface image formed at this time is changed on the photosensitive drum 10 such that it is a mirror image of the rear surface image (described later).

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

The recording paper P is driven by a timing roller 15e, which is a transfer material supply means, to drive the color toner image of the front surface image formed on the photosensitive drum 10 and the back surface image carried on the intermediate transfer body 14a. The sheet is fed to the transfer area 14b in synchronization with the color toner image. FIG. 3 shows the toner image formation state of the back side image carried on the intermediate transfer body 14a and the front side image formed on the photosensitive drum 10 and the recording paper P supplied in synchronization therewith.

When the recording paper P is fed to the transfer area 14b,
The recording paper P is charged by applying a direct current voltage of 4 to 6 kV having the same polarity as that of the toner by a paper charger 14f as a transfer material charging means, and is adsorbed on the intermediate transfer body 14a to be transferred to the transfer area 1
4b. By charging the paper with the same polarity as that of the toner, the toner image is prevented from being attracted to the toner image on the intermediate transfer member 14a and the toner image on the photosensitive drum 10, thereby preventing the toner image from being disturbed. Further, as the transfer material charging unit, a conductive roller, a conductive brush, or the like that can make contact with and release contact with the intermediate transfer member 14a can be used.

In the transfer area 14b, the peripheral surface of the photosensitive drum 10 is driven by a primary transfer unit 14c as a first transfer means to which a DC voltage of 4 to 6 kV opposite to the toner (positive polarity in this embodiment) is applied. The upper surface image is collectively transferred to the surface (upper surface) of the recording paper P (primary transfer B). At this time, the back side image on the peripheral surface of the intermediate transfer body 14a is
Is not transferred to the intermediate transfer member 14a.

The recording paper P on which the color toner image has been transferred on the surface thereof is then subjected to a secondary transfer as a second transfer means to which a DC voltage of 4 to 6 kV opposite in polarity to the toner (positive in this embodiment) is applied. The sheet is conveyed to the transfer device 14g, and the back surface image on the peripheral surface of the intermediate transfer body 14a is collectively transferred to the back surface (lower surface) of the recording paper P by the secondary transfer device 14g (secondary transfer).

Since the toner images of the respective colors overlap with 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 a double-sided image formation in which the polarity of the color toner image formed on the intermediate transfer member 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, the lower layer is formed. The toner is not sufficiently charged to the same polarity, so that 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 intermediate transfer member 14a without changing the polarity, and then the recording paper is changed without changing the polarity. The batch transfer to P is preferable because it contributes to the improvement of the transferability of the backside image formation. Also for the surface image formation, reversal development is repeatedly performed on the photoreceptor drum 10, and the color toner images of the same polarity formed by superposition are collectively transferred to the recording paper P without changing the polarity. It is preferable because it contributes to the improvement of transferability.

As described above, in color image formation, the first transfer means and the second transfer means are separately provided, and the first transfer means is operated to form a color toner image on the surface of the transfer material. Next, 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 unit is preferably adopted.

The recording paper P, which is a transfer material having a color toner image formed on both sides, is discharged by a paper separation AC discharger 14h in which a DC voltage and an AC voltage for transfer material separation are superimposed, and is discharged from the intermediate transfer member 14a. A fixing device 1 as a fixing unit that is separated (separated and neutralized) and includes two fixing rollers having a heating unit (heater) inside both upper and lower rollers.
7. The recording paper P is the first fixing roller 1 on the upper side.
Heat and pressure are applied between the recording paper P and the lower second fixing roller 17b, and the adhered toner on the front and back of the recording paper P is fixed.
c and is discharged to a tray 18d outside the apparatus. Reference numeral 18b denotes a reversing discharge unit for reversing and discharging a one-sided copy.

The toner remaining on the peripheral surface of the intermediate transfer member 14a after the transfer is provided to an intermediate transfer member cleaning device 14i, which is a means for cleaning the intermediate transfer member.
The blade 4a is cleaned by a blade capable of abutting and releasing. The toner remaining on the peripheral surface of the photoconductor drum 10 after the transfer is subjected to static elimination by the photoconductor drum AC static eliminator 16, reaches the cleaning device 19, and is made of a rubber material that contacts the photoconductor drum 10. The toner is scraped off into the cleaning device 19 by the cleaning blade 19a, and is collected by a screw 19b in a waste toner container (not shown). The photosensitive drum 10 from which the residual toner has been removed by the cleaning device 19 is subjected to uniform charge removal by the Y scorotron charger 11 after the peripheral surface of the photosensitive member is neutralized by exposure by the uniform exposure device 12c, and the next image is formed. Enter the formation cycle.

In an image forming apparatus in which toner images are formed on both sides of a recording sheet via the above-described intermediate transfer member and the image is fixed, a plurality of, for example, two sheets of images can be stored on the intermediate transfer member. In this case, by performing the following image forming process, it is possible to increase the number of processed double-sided copies formed per unit time.

FIG. 4 is an explanatory diagram showing a state of forming toner images when two toner images can be stored on the intermediate transfer member. First, on the photosensitive drum 10, image data serving as a first back image on a copy is exposed to an exposure unit 12.
The toner image written and developed is transferred onto the intermediate transfer member 14a by the primary transfer device 14c (FIG. 4A). On the photoreceptor drum 10, image data to be a second backside image on the copy is written by the exposure unit 12 after the first backside image on the copy, and the developed toner image is 1 The image is transferred onto the intermediate transfer member 14a by the next transfer device 14c. By this process, the first and second back images of the copy are carried on the intermediate transfer member 14a (FIG. 4B).

The writing of the first front image on the copy on the photosensitive drum 10 is started in synchronization with the first rear image on the intermediate transfer member 14a. Further, the first recording paper P is conveyed in synchronization with the first back image on the intermediate transfer member 14a, and the first recording sheet P is placed on the first back image of the intermediate transfer member 14a.
The first sheet of recording paper P adheres and is conveyed to the contact position with the photosensitive drum 10, and the first surface image is transferred to the surface of the first sheet of recording paper P by the primary transfer device 14c. (Fig. 4
(C)).

After the first surface image is transferred to the front surface of the first recording paper P, the first back image is transferred to the back surface by the secondary transfer unit 14g and separated from the intermediate transfer member 14a. Then, the first recording paper P carrying the double-sided image moves to the fixing device 17. In parallel with this operation, the intermediate transfer member 1
4a, the photosensitive drum 10 is synchronized with the second rear image.
A second front image is formed thereon, and a second recording paper P is conveyed in synchronization with the second rear image, and the second recording paper P is placed on both sides of the second recording paper P. The front and back images are carried. In this way, the first and second sheets of recording paper P are carried out onto the tray 18d at very short time intervals. (FIG. 4D).

The intermediate transfer member 14a, on which the first and second back side images have been transferred onto the recording paper, is cleaned by the intermediate transfer member cleaning device 14i.
Also, the residual toner is removed by the cleaning device 19, and the process enters the next third and fourth double-sided image forming cycle. Since the image is formed every two sheets in this way,
The number of double-sided copies formed per time is nearly twice as large as that of image formation for each sheet.

Here, the circuit configuration of the color image forming apparatus including the image reading section A, the image processing section B, and the image forming section D will be described with reference to the block diagram of FIG.

First, in the image reading section A, the three color separated analog image signals output from the image pickup device CCD are converted into digital image signals (image data) by an A / D converter B11. The data is output to the image processing unit B via the interface B12.

The digital image signal (luminance information) input to the image processing section B is first converted into density information by a density conversion section B13.

Then, a scaling process according to the user's scaling designation is performed by the enlargement / reduction processing unit B14. Further, the image discrimination processing unit B15 discriminates a character image or a photographic image based on the density information converted by the density conversion unit B13, and sets a filter characteristic in the filter processing unit B16 based on the discrimination result. The filter processing unit B16 performs a spatial filter process according to the above setting.

The image discrimination processing section B15 corresponds to the image discriminating means and the processing characteristic varying means in this embodiment. The discrimination between a character image and a photographic image is performed in a character image area in a mixed image of a character image and a photographic image. And determination of a photographic image area.

Here, a pair of data selectors B17 and B18 are provided in order to switch the filtering process and the scaling process in accordance with the designation of enlargement / reduction.
The switching between the filtering process and the scaling process is performed in order to prevent moiré of a halftone dot image seen in an image at the time of the reduction process.

On the other hand, the EE processing section B19 obtains histogram data in order to obtain the characteristics of the original image from the image information obtained by the pre-scan before the main scan. Then, the CPU of the image processing system (not shown) converts appropriate gamma correction data based on the histogram data into the gamma correction processing unit B20.
To provide.

The image data (density information) that has been subjected to the filtering process and the scaling process is subjected to γ correction processing according to the characteristics of the image forming apparatus B25 described later in the γ correction processing unit B20, and then to the image area It is output to the processing section B21. In the image area processing unit B21, in addition to the extraction of the effective image area of the document, area processing such as frame erasure and fold erasure is also performed.

The image data (density information) which has been subjected to all the image processing necessary for image formation as described above and which has been finally output to the image forming apparatus B25 to be described later is transmitted through the interface B22. Output to the unit D.

The image forming section D has a function of forming an image on the photosensitive drum 10 in real time when reading a document, and stores and holds a plurality of input image data. It has a data selector B91 for arbitrarily reading data later, an image correction process B92 for performing image correction corresponding to the front / back, and a function of forming an image from the corrected image data.

In this embodiment, the image data obtained by reading the original image as described above and having undergone all necessary image processing are stored, and the stored image data is The function of selectively reading and forming an image later is referred to as an electronic RDH function.

The image forming unit D includes, in addition to the image forming apparatus B25 such as a laser printer, an image storage unit B23 (image data storage unit) for storing image data in a rewritable manner in order to realize the electronic RDH function. Is provided, a data selector B91 for switching between the electronic RDH function and the normal real-time image forming function and for allocating image data on the front and back surfaces, and an image correction process B92 for performing image correction corresponding to front / back sides. Are provided.

The data selector B91 selectively selects one of the image data read from the image storage section B23 and the image data sequentially output from the image processing section B in response to the reading. Laser printer) B2
5 is output.

That is, the image storage unit B23 stores the image data in the final output state which is the same as when the normal real-time processing is performed, and the image data from the image processing unit B selectively output by the data selector B91. The image data and the image data read from the image storage unit B23 are treated equally in the image forming apparatus B25 so that an image can be formed.

In the image forming apparatus of the present invention, the back side image is transferred twice from the image forming body to the intermediate transfer body and twice from the intermediate transfer body to the recording paper. On the other hand, the surface image is transferred once from the image forming body to the recording paper. At the time of these transfers, the toner adhesion amount decreases by about 10% at a time, so that when the image processing is performed under the same conditions, the image density of the back side image is lower than that of the front side image. In the case of the back side image, the gradation is changed due to the scattering of the toner image due to the two transfers. In the case of a halftone dot image, a halftone dot tends to spread and γ generally tends to increase. Further, in a color image, since the overlapping order of the toner images is reversed on the recording paper, the color tone changes.
The UCR amount is obtained from the mixture ratio of the three colors Y, M, and C.
Since K tends to be the uppermost layer in the back side image and black (K) tends to be emphasized too much, it is necessary to change the UCR amount in color reproduction between the front side image and the back side image.

In the present embodiment, as shown in FIG. 6, in the color processing B921 of the image correction processing B92, the masking section performs color processing such as masking, inking, and UCR. As the masking, generally used linear masking or, when performing advanced color correction, non-linear masking or masking using a look-up table is used. Masking parameters for this color correction are set in advance for the front side image and the back side image, respectively.
The setting of the parameter is changed according to the front side or the back side. The color processing B921 and the γ conversion and filter processing B922 are performed, and the Y, M, C, and K colors are output to the exposure unit 12 through multivalue processing B923 such as screen angle, dither, and error diffusion. . Such image correction processing B92 is performed to form a double-sided image with adjusted image density and color tone. Since the back side image is subjected to two transfer steps, γ is likely to be higher than the front side image, and the resolution is also likely to be reduced. It has a function to correct this.

In the case of a monochrome image, color correction is not required, and γ correction, filter processing and density correction may be performed only on the back side image. If the maximum density of black is a saturated image density, γ correction If the parameter setting is changed only for the correction and the filter processing, a two-sided image with no difference between the front and back sides can be obtained.

In the above description, the mirror image conversion processing of the image data is performed by the data selector B91. However, the mirror image conversion processing is included in the parameters for changing the setting according to the front side or the back side in the image correction processing B92. It is also possible to adopt a circuit configuration including this.

In the present invention, after the initial document image is read by the image reading section A and the image data is transferred, or after the transfer of the image data is confirmed by an external input, the transfer of the transfer material is performed. The first and second back side images are formed on the intermediate transfer belt by transfer from an image forming body on the intermediate transfer belt before the transfer material is fed. The first and second sheet images are formed on the image forming body together with the feeding of the second sheet of the transfer material. As a result, the printing time when forming a double-sided image is reduced, the occurrence of a paper feed jam when a reading error occurs in the image reading unit A is prevented, and the time required for printing the first sheet is reduced.

Hereinafter, an embodiment will be described. (Embodiment 1) (Inventions of Claims 1 to 4) The image forming apparatus according to the present embodiment can easily cope with a document jam occurring during copying, and starts image formation of copies on both sides of the first sheet. It is characterized in that the time required to complete the process is shorter than that of the prior art. Prior to the description of the embodiment of the present invention, a point of time when image formation for duplex copying in the related art is started will be described. Prior Art 1: Image forming apparatus shown in conceptual diagram of FIG. 10 using double-sided reversing feeder Single-sided copied paper is re-fed via ADU (double-sided reversing feeder) and image is printed on the opposite side Is formed. In such a configuration, when the path length of the ADU is n sheets, image formation is started after image data of 2n pages is guaranteed (after all image data of both sides of the sheet entering the ADU is guaranteed). .

If image formation is started before 2n pages of image data are guaranteed, if a document jam or the like occurs, there is no place to go to one-sided copied paper, and the paper is wasted. turn into.

Specifically, when the ADU path length is three,
The image formation is started after the reading of the document on the sixth page is completed. When the ADU path length is two, the image formation starts after the fourth page of the original is read. As is apparent from this, in the prior art 1, the FCOT
(1st Copy Out Time) becomes considerably slow. Prior art 2: One-pass double-sided image forming apparatus shown in FIG. 1 using an intermediate transfer body An image is formed on both sides of a sheet via an intermediate transfer body (the same configuration as the present invention). When n images can be accommodated on the photosensitive member, the image data for 2n-1 pages is guaranteed (after the image data continuously formed on the intermediate transfer member is guaranteed). Start image formation.

If image formation is started before 2n-1 pages of image data are guaranteed, if a document jam occurs, a space is created on the intermediate transfer member, and paper feeding and image The formation sequence is complicated. However, the sheet is not wasted as in the prior art 1 (since only cleaning the toner on the intermediate transfer body is sufficient).

More specifically, when two sheets can be stored on the intermediate transfer member, the back images formed on the intermediate transfer member are the first page and the third page. This is after the reading of the original is completed.

The prior art 2 is different from the prior art 1 in FCOT.
Is significantly shorter, but the image forming apparatus according to the present embodiment has an improved sequence in order to further shorten the FCOT compared to the prior art 2.

In the image forming apparatus of the present embodiment, for example, a document presence / absence detecting means S1 for detecting the presence / absence of a document at the position of the document placing table of the image reading section A is provided, and information from the document presence / absence detecting means S1 is used. When the image data of the first page is input and it is determined that the image data of the third page does not exist when the toner image of the second page can be stored on the intermediate transfer member, the image of the second page is It is characterized in that it has a sequence for starting the formation of a toner image based on the image data of the first page irrespective of data input.

FIG. 7 shows the reading of a document image by the image reading section A when reading a double-sided document and the exposure unit 1.
FIG. 4 is an explanatory diagram showing a relationship between writing of an image by No. 2 and paper feeding by a timing roller 15e. A mode for creating a two-sided image copy from a two-sided original is selected on an operation panel (not shown), and reading of the original image is started by turning on a start button for image recording. That is, the first document is discharged from the document mounting table of the image reading unit A, and stops with the surface facing down on the platen glass 55,
The reading of the table of the first document (hereinafter, also referred to as one table) is started. While reading the front image, the document presence detecting means S
The presence / absence of the second document (image data of the third and fourth pages) is detected by 1.

Second original (image data of third page)
When it is detected that there is no, as shown in FIG.
1 regardless of the input of the image data of the back (2nd page)
The formation of a toner image based on the image data of the table (first page) is started. That is, the read one table data is temporarily stored in the image storage unit B29, but as soon as it is confirmed that there is no second document (image data of the third page), the first table data (the first page) is read. The image data is called, the mirror image processing is performed by the data selector B91, the image processing corresponding to the front / back side is performed by the image correction processing B92, and the image is formed on the photosensitive drum 10, and the formed image is formed on the photosensitive drum 10. Is transferred onto the intermediate transfer member 14a.

After reading the front (first page) image, the read back (second page) image is also stored in the image storage unit B.
29, and is synchronized with the front (first page) image on the intermediate transfer member 14a from the image storage B29 to the back (2).
(Page number) The image is called and the photosensitive drum 10 is called.
An image is formed on the upper side. Further, in synchronization with the writing of the first back (second page) image on the photosensitive drum 10, the first recording paper P is transferred to the transfer area 14 by the timing roller 15e.
b. The first back (second page) toner image is transferred to the front surface of the recording paper P by the primary transfer unit 14c, and the first table (first page) toner image is transferred to the back surface by the secondary transfer unit 14g.
The recording paper P having the toner image transferred on both sides thereof is separated from the intermediate transfer body 14a, is fixed by the fixing device 17, travels straight, and is discharged by the discharge roller 18c into the tray 18d.
It is carried up.

In the embodiment shown in FIG. 7A for reading a double-sided original, the presence or absence of image data of the second original (the third page) in the process of reading the image of the first table (the first page). Is detected, the image formation can be started immediately when it is determined that there is no image data of the third page, and the sequence minimizes the FCOT of the double-sided copy when reading the double-sided original. In the present embodiment, the image data of the second page is guaranteed at the start of sheet feeding.

FIG. 7 (b) shows the case where two-sided originals are read.
This shows a sequence when it is detected that the original (the third page of image data) is present. In this case, image formation is performed such that two pages of toner images are carried on the intermediate transfer member 14a. 2 is placed on the intermediate transfer member 14a.
Because of carrying the toner image of the table (3rd page), writing of the image of the 1st table (1st page) is performed during reading of the image of the 2nd table (3rd page).

FIG. 8 shows the reading of a document image by the image reading unit A when reading a single-sided document and the exposure unit 1.
FIG. 4 is an explanatory diagram showing a relationship between writing of an image by No. 2 and paper feeding by a timing roller 15e. Select the mode to create a two-sided image copy from a one-sided original on the operation panel,
The reading of the document image is started by turning on the start button. The first page document is discharged from the document table, stopped on the platen glass 55, and the first page (hereinafter, also referred to as 1P) image is read. When reading of the 1P image is completed, the original of the first page is discharged from the platen glass 55, and the original of the second page is conveyed from the original mounting table toward the platen glass 55. When the document on the second page is discharged from the document mounting table, the document presence / absence detecting means S1 detects the presence / absence of the document on the third page while the document on the second page is being read.

When it is detected that there is no third page original (3P image data), as shown in FIG. 8A, the toner based on the first page image data regardless of the input of the second page image data. Image formation begins. That is, the read 1P image data is once stored in the image storage unit B29, but as soon as it is confirmed that there is no 3P image, the 1P image data is called up, mirror image processing is performed by the data selector B91, and table display is performed by the image correction processing B92. The image processing is performed on the photosensitive drum 10 by performing the image processing corresponding to the reverse, and the formed 1P toner image on the photosensitive drum 10 is transferred onto the intermediate transfer member 14a.

Reading of 1P image and reading of 2P
The P image is also stored in the image storage unit B29, but the 2P image is called from the image storage unit B29 in synchronization with the 1P toner image on the intermediate transfer body 14a, and the image is formed on the photosensitive drum 10. Photoreceptor drum 10 for 2P images
The first sheet of recording paper P is transferred to the transfer area 14
b. A 2P toner image is formed on the surface of the recording paper P,
The 1P toner image is transferred to the back surface, fixed, and carried out onto the tray 18d.

In the embodiment shown in FIG. 8A for reading a single-sided original, the presence of a 3P image cannot be determined at the stage when the reading of the first page of the original is completed. It is during reading or after reading is completed. With this sequence, the FCOT of double-sided copying when reading one-sided originals is set to the shortest time.

FIG. 8 (b) shows the state when reading a one-sided original.
This shows a sequence when it is detected that image data of the page exists.

Since a double-sided image is formed by such a process, if a transfer trouble of image data occurs due to a document jam or the like, the intermediate transfer member 14a and the photosensitive drum 10 are immediately cleaned to supply the transfer material. Prohibit sending. After the document jam or the like is released by the user, the transfer of the image data of the back side image is resumed, and the image formation on the photosensitive drum 10 is performed. If a transfer trouble occurs in the image data after the start of feeding the transfer material, all the image data to be formed on the transfer material being transported is guaranteed. Then, the next image formation is prohibited.

By forming an image on both sides of the transfer material in the order described above, the FCOT can be set to the shortest time, and a paper feed jam can be performed even if an error such as a document conveyance trouble during image reading occurs. Such a situation does not occur, and extremely efficient image processing is performed. (Embodiment 2) (Claims 5 to 9) In the image forming apparatus of the present embodiment, two pages of toner images can be stored on the intermediate transfer member, and the transfer of the toner image onto the intermediate transfer member can be performed. A first mode shown in the sequence of FIG. 9A in which the direct transfer of the toner image onto the transfer material is repeated every two pages, and a second mode shown in the sequence of FIG. It is characterized by having. In the first mode, the supply of heat from the heater inside the heat roller is insufficient for the amount of heat taken away by the passage of the transfer material by the fixing device, and the temperature of the heat roller surface decreases. On the other hand, in the case of the second mode, the fixing device is supplied with a sufficient amount of heat with respect to the amount of heat taken by the transfer material, so that the fixing condition reduced by the image formation in the first mode can be returned to an appropriate fixing condition. Have.

According to the present invention, duplex printing is performed by appropriately switching the image formation between the first mode and the second mode according to the situation.

(1) In this embodiment, the first mode and the second mode are selected according to the type of the transfer material. For example, when the transfer material is thick paper, the fixability is not good as compared with plain paper. Further, the amount of heat taken from the fixing device at the time of fixing is larger than that of plain paper.
Therefore, the first mode is selected for plain paper, and the second mode is selected for thick paper. The detection that the transfer material is thick paper is performed by designating the thick paper provided on the operation panel or by detecting the thick paper by the paper thickness detection means provided in the transfer material feeding path. By switching to the image formation in the second mode by the detection of the thick paper, a good two-sided copy can be continuously obtained even when the thick paper is used as the transfer material.

(2) This embodiment has a plurality of transfer material supply units, and the first mode and the second mode are provided in accordance with the selected transfer material supply unit.
Mode and select. When using thick paper as a transfer material, for example, thick paper is not suitable for feeding along a transport path that is stiff and has a small radius,
Paper is fed from a manual paper feed unit having a linear transport path. The paper feed roller 15d is provided in the manual paper feed section 15c.
And feeds the transfer material inserted into the manual paper feed unit 15c. The manual transfer material presence / absence detecting means S2 detects the presence or absence of the manual transfer material in the manual paper feed unit 15c or the manual paper feed path.
Is provided, and when it is detected that a manual transfer material is present, the sequence is switched so that image formation in the second mode is performed. By performing such switching, a good double-sided copy can be obtained at a specified fixing temperature for thick paper inserted into the manual paper feed unit 15c.

In addition to the above, when a plurality of paper feed cassettes are provided as the transfer material supply unit and a specific paper feed cassette is set to be loaded with thick paper, a specific paper feed cassette is provided. Control is performed so as to switch to image formation in the second mode upon detection of paper feeding from a copy unit. By switching to the second mode, good two-sided copying can be continuously obtained for thick paper fed from a specific paper feed cassette.

(3) In this embodiment, when image formation is performed continuously, the first mode and the second mode are selected according to the number of pages. When continuous double-sided copying is performed in the first mode, the surface temperature of the heat roller gradually decreases, and finally, a fixing failure occurs. In the present embodiment, image formation is performed by repeating an image forming program in which, for example, a 6-page double-sided copy in the first mode is combined with a 1-page double-sided copy in the second mode. When an image is formed by such a program, the surface temperature of the heat roller becomes lower than the initial fixing temperature (however, the temperature is not so low as to cause a fixing defect) due to double-sided copying of, for example, six pages in the first mode. The heat roller surface temperature that has dropped during one-page double-sided copying in the second mode returns to the initial fixing temperature,
Continuous and efficient continuous copying is enabled.

(4) This embodiment has a temperature detecting means for detecting the temperature of the fixing section, and selects the first mode or the second mode according to the detection result. The fixing unit is provided with temperature detecting means (not shown) for detecting the surface temperature of the heat roller, and the temperature of the fixing unit is controlled. The first mode and the second mode are determined by the temperature detected by the temperature detecting means. Perform selection control.
In this embodiment, the normal fixing temperature T ₀ and the fixing failure temperature T ₁
And the temperature T _{2 at} which the mode switching of this embodiment is performed.
(T ₀ > T ₂ > T ₁ ) is provided. When performing continuous copying, double-sided copying is continuously performed in the first mode. During which the temperature sensing means have performed the temperature sensing of the heat roller surface, the detection temperature of duplex copying continuously performs mode switching to the second mode from when detecting the decreased first mode until T _2. Continue the temperature detection of the fixing unit in the image formation by the second mode, the detected temperature returns to the first mode again when it detects that the rose to T _0. By such control, a good double-sided copy can be obtained continuously.

By using a combination of the first mode and the second mode as shown in the above embodiments (1) to (4), high-speed processing can be performed without stopping image formation halfway. High-quality double-sided copies can be obtained continuously.

[0109]

According to the first to fourth aspects of the present invention, the time until the first printed double-sided copy is discharged onto the tray is shortened, and a trouble in transporting image data which is likely to occur at the beginning of image reading. Thus, paper jams and the like do not occur even if mistakes are made, and extremely efficient image processing is performed. In the case of the fifth to ninth aspects, high-quality copy images can be obtained by high-speed processing without continuous pause of double-sided copying.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of an image forming apparatus of the present invention.

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

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

FIG. 4 is an explanatory diagram showing a toner image forming state when two toner images can be stored on an intermediate transfer member.

FIG. 5 is a block diagram showing a circuit configuration.

FIG. 6 is a block diagram illustrating a circuit configuration of an image correction process.

FIG. 7 is an explanatory diagram showing a relationship between image reading, image writing, and sheet feeding of a two-sided document according to the first embodiment;

FIG. 8 is an explanatory diagram showing a relationship among image reading, image writing, and sheet feeding of a single-sided document according to the first embodiment.

FIG. 9 is an explanatory diagram illustrating a relationship (first mode and second mode) among image reading, image writing, and sheet feeding according to the second embodiment.

FIG. 10 is a conceptual diagram of an image forming apparatus used in Conventional Technique 1.

DESCRIPTION OF SYMBOLS 10 Photoreceptor drum 11 Scorotron charger 12 Exposure unit 13 Developing device 14a Intermediate transfer member 14c Primary transfer device 14g Secondary transfer device 15c Manual feed unit 18d Tray A Image reading unit B Image processing unit D Image Forming part B11 A / D converter B13 Density converting part B16 Filter processing part B19 EE processing part B20 γ correction processing part B21 Image area processing part B23 Image storage part B91 Data selector B92 Image correction processing (part)

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Kuki Nagase, Inventor 2970, Ishikawacho, Hachioji-shi, Tokyo Konica Corporation F-term (reference) 2H027 DA12 DA46 DC19 ED06 ED30 EE01 FA11 ZA07 2H028 BA03 BB02 BB06 2H032 BA09 BA12 CA13

Claims (9)

[Claims] 1. A toner image is formed on an image forming body based on image data input in page order, and the formed toner image is transferred via an intermediate transfer body or directly onto a transfer material.
When two pages of toner images can be stored on an intermediate transfer member in an image forming apparatus that forms toner images on both sides of a transfer material, image data of the first page is input and image data of the third page is input. An image forming apparatus which starts forming a toner image based on image data of the first page regardless of input of image data of the second page when it is determined that there is no image data. 2. The image forming apparatus according to claim 1, wherein, when image data is sequentially input by reading a double-sided original, the presence or absence of image data of three pages is determined when the first original is read. apparatus. 3. The image forming apparatus according to claim 1, wherein when image data is sequentially input by reading a single-sided original, the presence / absence of image data of three pages is determined when the second original is read. apparatus. 4. The image forming apparatus according to claim 1, further comprising means for designating a one-sided document or a two-sided document. 5. A toner image is formed on an image forming body based on image data input in page order, and the formed toner image is transferred to a transfer material via an intermediate transfer body or directly.
When an image forming apparatus that forms an image on both surfaces of a transfer material can store two pages of toner images on the intermediate transfer member, the transfer of the toner image onto the intermediate transfer member and the transfer of the toner image onto the transfer material A first mode in which direct transfer is repeated every two pages,
An image forming apparatus having a second mode that repeats for each page. 6. A first mode and a second mode according to a type of a transfer material.
The image forming apparatus according to claim 5, wherein a mode is selected. 7. The image forming apparatus according to claim 5, further comprising a plurality of transfer material supply units, wherein the first mode and the second mode are selected according to the selected transfer material supply unit. . 8. The image forming apparatus according to claim 5, wherein, when image formation is performed continuously, the first mode and the second mode are selected according to the number of pages. 9. The image according to claim 5, further comprising a temperature detecting unit for the fixing unit, wherein the first mode and the second mode are selected according to a result of the detection. Forming equipment.