JPH08240994A - Image forming device - Google Patents

Abstract

PURPOSE: To surely prevent staining on the rear side of a transfer paper by completely removing toner transferred to a part except an image forming region on a transfer belt. CONSTITUTION: This image forming device is composed of a paper feeding part 11 housing the transfer paper having size previously set in a device main body, a manual paper feeding part 12 which is different from the feeding part 11 and for feeding a standard size or nonstandard size transfer paper including different size toward the transfer belt and a cleaning member for removing the toner transferred from a photoreceptor 1 to the transfer belt 5A. Further, the image forming device is provided with a control part which is connected to the driving part of the transfer belt 5A and can detect the size of the transfer paper fed from the manual paper feeding part 12 and the opening/closing states of an original cover member 3B installed on an original platen and continue the cleaning of the transfer belt 5A for a specified time, after a toner image is transferred, only when the toner image is transferred to the transfer paper fed from the manual paper feeding part 12, while the original cover member 3B installed on the original platen 3A is opened.

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,
More specifically, the present invention relates to a transfer device used in a transfer process performed by an electrophotographic method.

[0002]

2. Description of the Related Art Generally, an image forming apparatus using an electrophotographic system includes an electrophotographic copying machine, a printer or a facsimile machine. In electrophotographic image formation, an electrostatic latent image is formed on a uniformly charged photoreceptor by exposure or optical writing, and this electrostatic latent image is formed into a two-component mixture of magnetic carrier and toner. A toner image obtained by processing a visible image with a toner using a system developer is transferred onto a transfer paper or the like to obtain a copy.
The configuration used for transferring the toner image onto the transfer paper includes:
There is a contact type transfer structure using a belt instead of corona discharge. In this structure, a transfer belt wound around a pair of rollers faces a photoconductor, and the transfer paper is brought into contact with the photoconductor while electrostatically adsorbing the transfer paper on the belt surface, and a transfer bias is applied in this state. As a result, electrostatic transfer of toner onto the transfer paper is performed.

By the way, when an electrostatic latent image is formed on a photosensitive member, an image portion and a non-image portion are distinguished from each other depending on the presence or absence of reflected light from a document. For this reason, when the size of the original is smaller than the size of the transfer paper to be copied, if the original is exposed without being blocked by the pressure plate provided on the original placing table on which the original is placed, the original will be exposed. Since the reflected light from the portion other than the placement area is not reflected by the light receiving portion such as the image reading portion, the state becomes the same as that of the black image. Therefore, on the photoconductor, a portion other than the original placement area corresponding to the transfer paper size is formed as a black image, and a portion other than the area originally to be transferred to the transfer paper as an image appears as a black image. As a result, the amount of toner consumed becomes larger than the amount used for actual image formation. In this way, the toner adhering to the area other than the original placement area is transferred onto the transfer paper in addition to the area corresponding to the original size, and an extra black solid area is formed around the transfer image. As a result, a copy image that is formed and does not look good is obtained. Further, when the transfer sheet size and the document size when the pressure plate is exposed without blocking the document are the same, the size of the document is not more than the maximum size of the document placing area on the document placing table. If so, the black solid image formed in the area obtained by subtracting the original size from the maximum size of the original placement area is transferred to the transfer belt that contacts the photoconductor.

If the toner transferred to the transfer belt adheres to a portion other than an area where an original image is formed on the transfer paper, the transfer paper having a size larger than the image forming area corresponding to the preceding original size is formed. Then, when it is adsorbed on the transfer belt, it adheres to the back surface of the transfer paper, and stains the back of the transfer paper.

Therefore, in order to reduce the amount of toner that adheres to areas other than the image area that should be originally formed, the developing device is configured to dissipate the charged charges on the photoconductor other than the image forming area corresponding to the size of the original document by light irradiation. There has been proposed a structure in which an erasing operation for preventing the adhesion of the toner to be supplied is carried out (for example, Japanese Utility Model Laid-Open No. 178854/1988, Japanese Patent Laid-Open No. 151889/1990, Japanese Utility Model Laid-Open No. 63-16).
2362).

[0006]

However, in the image forming apparatus, not only the paper feeding unit which is provided inside the main body of the apparatus and which feeds the transfer paper of a known size, but also the paper feeding unit There may be a case where a sheet feeding unit for transfer sheets of different sizes having different sizes is provided. Such a paper feeding unit is provided as a manual paper feeding unit in the apparatus body, and when feeding transfer sheets of different sizes, the manual paper feeding unit is used to install the paper feeding unit in the apparatus main body. Transfer papers of different sizes can be delivered to the resist section.

For this reason, when the transfer paper is fed from the paper feed unit provided inside the apparatus main body, a portion other than the image forming area on the photoconductor is selected according to the selected transfer paper size. Although it is possible to dissipate the electric charge by the erasing work described above, in the case of the transfer paper fed from the manual paper feeding unit, its size is often unknown in advance. Erase work may not be possible in some cases. In particular, in the case of manual feeding, the size of the image forming area on the photoconductor is, for example, A
The maximum size such as 3 sizes is set so that the image formation can be performed regardless of the size of the transfer paper to be fed. Therefore, when the size of the transfer paper is smaller than the size of the image forming area, for example, A4 size, and the original is not covered by the pressure plate, the difference between the size of the original and the size of the image forming area is large. Thus, the area corresponding to the difference is formed as a black solid image. As a result, the toner attached to the area other than the size of the transfer paper is transferred to the transfer belt.

Therefore, as a structure for removing the toner transferred to the transfer belt, there is a structure provided with a belt cleaning device including a blade that contacts the transfer belt. In the above configuration, after the image is transferred onto the transfer sheet at an arbitrary position of the transfer belt facing the photoconductor, the transfer sheet is again faced to the photoconductor and then transferred onto the transfer sheet from the time when the transfer sheet is conveyed toward the fixing device. The toner remaining on the surface of the transfer belt is scraped during one cycle of the moving process until the image is transferred to a position where it can be transferred.

However, in such a structure, since it is premised that the toner remaining in the image forming area on the transfer belt is scraped off, since the toner is transferred to a portion other than the image forming area, Originally, there were cases where it was not possible to sufficiently scrape off all of the toner that adhered to the image forming area in the course of one cycle of movement of the transfer belt. For this reason, the toner that has transferred to areas other than the image forming area on the transfer belt is not completely removed, and there is a risk that back stain may occur depending on the size of the transfer paper that is fed next.

Therefore, in view of the above problems in the conventional image forming apparatus, an object of the present invention is to provide an image forming area on a transfer belt in an image forming apparatus equipped with a transfer device for transferring a toner image by contacting a photoconductor. Other than that, it is an object of the present invention to provide an image forming apparatus capable of completely removing the transferred toner and reliably preventing the backside of the transfer paper from being stained.

Another object of the present invention is to prevent backside smearing of transfer paper regardless of whether the transfer paper has a fixed size or a fixed size when continuous copying is performed by manual feeding. An object is to provide an image forming apparatus.

Another object of the present invention is to provide an image forming apparatus capable of shortening the time for preventing backside smearing of transfer paper when the same size transfer paper is manually fed. It is in.

[0013]

In order to achieve this object, the invention according to claim 1 sensitizes a toner image carried on a photoconductor according to the contents of a document placed on a document table. In an image forming apparatus having a transfer structure that transfers onto a transfer sheet using a transfer belt that can contact the body, a transfer sheet of a predetermined size that is installed in the apparatus main body is accommodated, In addition, a sheet feeding unit for feeding the sheet toward the transfer belt and a sheet feeding unit provided separately from the sheet feeding unit, which has a standard size or a non-standard size including a size different from the transfer sheet accommodated in the sheet feeding unit. A manual feed unit capable of feeding a fixed-size transfer sheet to the transfer belt, a cleaning member provided so as to be able to contact the transfer belt, and a drive unit of the transfer belt are connected, Manual feed section above And a control unit capable of detecting the size of the transfer sheet fed from the original and the open / closed state of the document pressing member installed on the document mounting table, the control unit being installed on the document mounting table. Only when the toner image transfer is performed on the transfer paper fed from the manual paper feed section when the document pressing member is open, the transfer belt cleaning is continued for a predetermined time after the toner image transfer. The feature is to let.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the control section determines whether the transfer sheet fed from the manual sheet feeding section has a fixed shape or an irregular shape. When the original pressing member is open, and when the original is fixed, the transfer belt is transferred only after the toner image is first transferred onto the transfer paper fed from the manual paper feeding unit. The cleaning is continuously performed for a predetermined time, and when the toner image has an irregular shape, the transfer belt is continuously cleaned for a predetermined time each time the toner image is transferred onto the transfer paper.

According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, the control section detects by a sensor arranged in a feeding path of the transfer sheet fed from the manual sheet feeding section. The shape is fixed according to the length of the transfer paper
It is characterized by distinguishing irregular forms.

According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the control section supplies the manual feed during a time required for transferring the toner image. Whether the size of the transfer paper fed from the paper unit is changed or not is determined, and when the size is not changed, the transfer belt is not cleaned every time the toner image is transferred.

According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect, the control section determines whether or not the size has been changed based on the presence or absence of a transfer sheet in the manual sheet feeding section. I am trying.

[0018]

According to the first aspect of the present invention, when the toner image transfer is performed on the transfer sheet fed from the manual sheet feeding section when the document pressing member installed on the document placing table is opened. Only after the toner image transfer, cleaning of the transfer belt is continued for a predetermined time.

According to the second to fifth aspects of the invention, the transfer belt is cleaned every time the toner image is transferred, only when the irregularly shaped transfer paper is fed from the manual paper feeding unit and when the size is changed. Be done.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the embodiments shown in the drawings.

FIG. 1 is a schematic diagram schematically showing the overall structure of an image forming apparatus according to an embodiment of the present invention. In FIG. 1, the photoconductor has a drum shape and can rotate in the direction of the arrow shown. The photosensitive drum 1 has a photosensitive layer formed of an organic material such as OPC on its surface, and the charging device 2 uniformly charges the photosensitive layer. An electrostatic latent image is formed on the photosensitive drum 1 uniformly charged by the exposure device 3 or the writing device, and the electrostatic latent image is subjected to a visual image processing by the developing device 4 to form a toner image. Exposure device 3
Is for exposing the original placing table 3A installed on the upper surface of the apparatus main body, the original pressing member 3B for covering the original placed on the original placing table 3A, and the original placed on the original placing table 3A. The illumination lamp 3C and the plurality of reflecting mirrors 3D forming an exposure light path for the photosensitive drum 1 and the imaging lens 3E.

The photosensitive drum 1 on which the toner image is formed by the developing device 4 is adapted to electrostatically transfer the toner image carried on the transfer paper fed from the paper feed path 6 by the transfer device 5. ing.

In the case of the present embodiment, the transfer device 5 is provided with a transfer belt 5A which is wound around a pair of rollers to form a part of the transfer paper conveyance path, and the transfer belt 5A with respect to the photosensitive drum 1. Can be contacted. Therefore, the transfer sheet S01 whose delivery timing is set from the feeding path 6 by the registration roller 7 is
The toner image on the photosensitive drum 1 can be electrostatically transferred via the transfer bias from the transfer belt 5A side by being able to contact the surface of the photosensitive drum 1 by A. The transfer belt 5A is wound around a pair of rollers as described above, and one of the rollers is driven by a drive motor that is a drive source. The rotation timing of the drive motor is set by the control unit 15 described later.

Photoreceptor drum 1 after transfer of the toner image
The toner and residual charge remaining on the surface are removed by a cleaning device 8 and a charge eliminating lamp 9 which are installed at a position that has passed the transfer device 5, and are prepared for the next image formation.

A fixing device 10 for fixing the toner image is arranged behind the transfer paper on which the toner image is transferred by the transfer device 5 in the conveying direction.

The feeding path 6 is provided in the main body of the apparatus and has a transfer sheet conveying path S01 that is fed from a paper feeding cassette 11 that accommodates a transfer sheet of which size is known in advance and a manual sheet feeding described later. Transfer paper S02 delivered from section 12
Is extended toward the transfer device 5 from a position where the transfer path of the transfer roller 5 merges with the transfer path, and a registration roller 7 for setting the transfer timing with respect to the toner image on the photosensitive drum 1 and feeding the transfer sheet is disposed in the middle thereof. There is.

The manual paper feed section 12 is provided with a manual paper feed tray 12A which is provided on the side wall of the apparatus main body so as to be up and down and a transfer paper S02 inserted from the manual paper feed tray 12A.
It is composed of a payout roller 12B rotatable in a direction in which the payout roller 12B can be paid out.

The transfer device 5 is provided with a belt cleaning device 13 for removing the residual toner adhering to the transfer belt surface after the image transfer. The belt cleaning device 13, as shown in FIG.
A transfer belt 1 including a blade 13A capable of abutting on A and having finished transfer of the transfer paper and conveyance toward the fixing device 10.
When the blade 13A comes into contact with the surface of 2A, the toner remaining on the belt surface is scraped and collected. The blade 13A is the transfer belt 5
Since it is provided so as to be able to abut against A, it can be separated from the transfer belt 5A at the time of replacement, whereby rubbing against the transfer belt 5A can be prevented.

An eraser 14 is arranged at a front position facing the developing device 4 in the rotation direction of the photosensitive drum 1.

Although not shown in detail, the eraser 14 is of an array type in which a plurality of LED elements are arranged in parallel along the main scanning direction corresponding to the axial direction of the photosensitive drum 1. The controller 15 described later turns on the LED element at the selected position in the main scanning direction, and all the LEDs in the sub scanning direction which is perpendicular to the main scanning direction and corresponds to the transfer paper feeding direction. The element can be turned on.

The eraser 14 reduces the potential on the photosensitive drum 1 irradiated with the light from the LED element and weakens the electrostatic attraction force of the toner by the developing device 4 to prevent the toner from adhering. To do.

As shown in FIG. 3, the control unit 15 includes a CPU
It has a main controller composed of 15A, and its C
To the PU 15A, a gate array 15B, an operation panel 15C, and a RAM 15D are connected to the input side via an I / O interface (not shown) so that data can be transferred, and a driver 15E is further connected to the output side.

The gate array 15B includes a paper end sensor 16, a registration sensor 17, and a paper length detection sensor 1.
8, a paper discharge sensor 19 and a pressure plate opening / closing sensor 20 are connected. The paper end sensor 16 is used in the manual feed tray 1.
It is arranged in front of the feeding side of the different size transfer sheet S02 in 2A, detects the presence or absence of the different size transfer sheet S02 on the manual feed tray 12A, and detects the different size transfer sheet S02.
If there is no, it will output a signal. The paper end sensor 16 can also detect when the transfer sheet fed from the manual feed tray 12A is replaced.

The registration sensor 17 is provided in the paper feed cassette 11
Alternatively, the leading end of the transfer sheet fed from the manual feed tray 12A is detected, and the detection signal is used to set the driving force transmission timing of a clutch mechanism (not shown) that controls the rotation drive transmission of the registration roller 7. There is.

The paper length detecting sensor 18 is used for the manual feed tray 1
Targeting the different size transfer sheet S02 fed from 2A, the length in the feeding direction is detected, and a signal for discriminating between the standard size and the irregular size can be output.

As shown in FIG. 4, the pressure plate opening / closing sensor 20 is provided in the optical plate 20A and the pressure plate 3A provided on the original placing table 3A, and shuts off the optical path of the optical sensor 20A when the pressure plate 3A is closed. And a sector 20B, which outputs a detection signal when the open state of the pressure plate 3A is detected.

As shown in FIG. 5, the operation panel 15C includes a paper feed selection section, a copy number setting section, and a density setting section. The paper feed selection unit is provided in the main body of the apparatus and has a selection key 15C1 of the paper feed cassette 11 that contains transfer paper of a known size and the size of the transfer paper stored in the paper feed cassette 11. 15C2 for selecting a case where a different size transfer paper other than the above is manually inserted, and a size display portion 15C when the paper feed cassette 11 is selected
3 and 3 when manual feed is selected Manual transfer irregular key 15C4 for selecting the case where the different size transfer paper is irregular
It has and. The copy number setting section includes a number setting ten key 15C5, and the density setting section includes a setting key 15C6 and a display section 15C7. In FIG. 4, reference numeral 15
Reference numeral C8 indicates a number display section set by the number setting ten key 15C5, and reference numeral 15C9 indicates a print start key.

The driver 15E connected to the output side of the CPU 15A is connected to a drive motor (not shown) corresponding to a load in the main body of the apparatus and an eraser 14, and the drive motor includes a registration roller 7 and a transfer device. 5, a driving roller, a feeding roller provided in a transfer paper conveying system, and fixing and pressure rollers in the fixing device 10 are connected via a transmission mechanism (not shown). The drive motor is not limited to being used alone, but may be provided in each drive system, and it is advantageous to use each drive system in that the transmission mechanism can be simplified. .

The control unit 15 executes the image forming process by applying a timing pulse for performing the sequence control of the image forming process with the clock as a reference, and at the same time, transfers the image in accordance with the selected transfer paper size. Drive control of the device 5 and the eraser 14 is performed. The drive control of the transfer device 5 is performed according to the selection content of the transfer sheet to be fed, in this case, the transfer belt 5A according to the feeding from the paper feed cassette 11 and the feeding from the manual feed tray 12A.
The drive timing of is set. When the transfer paper S01 is fed from the paper feed cassette 11, the control unit 15 knows the size of the transfer paper S01 contained in the selected paper feed cassette 11, and thus the photosensitive paper is exposed according to the size. Erase work is performed on the body drum 1.

On the other hand, since the size of the different size transfer paper S02 fed from the manual feed tray 12A is not known, the length in the sub-scanning direction is detected by the paper length detecting sensor 18 at that time. Erase work on the photosensitive drum 2 in the direction is started. Erase work is targeted in both the main scanning direction and the sub-scanning direction. For this reason,
Different size transfer paper S fed from the manual feed tray 12A
The erasing operation in the sub-scanning direction in 02 is the maximum on the photosensitive drum 1 along the direction from the time when the paper length detection sensor 18 detects the trailing end of the different size transfer sheet S02 in the feeding direction. The erase operation is performed up to the end of the image forming area, and the erase operation in the main scanning direction is not performed.

The erasing operation described above is performed only when the open state of the pressure plate 3B is detected by the pressure plate opening / closing sensor 20. Therefore, in the main scanning direction, when an image having a size equal to or smaller than the maximum image forming area is formed on the photosensitive drum 1 and the image is transferred to the transfer paper, the image forming size is larger than the size of the maximum image forming area. And a toner is attached to a region corresponding to this difference, and the toner is transferred to the transfer belt 5A in the transfer device 5.

Therefore, in the present embodiment, the drive timing of the transfer belt 5A in the transfer device 5 is set to the paper feed cassette 11.
The drive is set to be driven for a longer time than when the image is transferred to the transfer sheet fed from. As the drive time of the transfer belt 5A, when the transfer paper size data indexed by the paper length detection sensor 18 to the size of the maximum image forming area corresponds to the standard size, the maximum image The time required to scrape off all the toner adhering to the area corresponding to the difference between the area of the forming area and the area of the standard size is set, and in the case of the non-standard size that does not correspond to the standard size, the image is The time is set so that all the toner transferred to the transfer belt 5A is scraped off when the size of the formation area is set to the minimum. The minimum size of the image forming area includes not only the minimum original at the same size but also the case where an image is formed on the photosensitive drum 1 by reducing and scaling the original. As a result, even when the erasing operation in the main scanning direction is not performed, the toner that has transferred to the transfer belt 5A regardless of the amount of toner that has transferred to the transfer belt 5A due to the formation of an image of that size or smaller in the maximum image forming area Will be scraped off.

Since this embodiment has the above-mentioned structure,
The procedure will be described with reference to the flowchart for explaining the operation of the control unit 15 as shown in FIG. In addition,
The flowchart shown in FIG. 6 is intended for the case where the size of the transfer paper S01 fed from the paper feed cassette 11 is A4 size. In FIG. 6, when the print start key 15C9 (see FIG. 5) is operated (S
1) According to the key selection in the paper feed selection unit, it is determined whether the paper is manually fed (S2). When it is determined that the sheet is not manually fed, it is determined whether the sheet is fed from the sheet feeding cassette 11 based on the key operation result in the sheet feeding selection unit (S
3) Data (Ps) relating to the transfer paper size is stored as (A4) according to the selected transfer paper size (A4) (S4), and the normal copy subroutine is executed according to this size data (S5). . In the normal copy subroutine, the erase operation controls the lighting of the LED elements in the main scanning direction and the sub scanning direction in accordance with the size data. The drive timing of the transfer belt 5A in the transfer device 5 is a belt cleaning operation in one cycle of movement, considering that the electric charge remaining in the non-image forming area on the photosensitive drum 1 is dissipated by the erasing operation. The time is set to scrape off the residual toner by the device 13.

On the other hand, when it is determined that the sheet is manually fed by the key operation in the sheet feeding selection section, the pressure plate opening / closing sensor 20
It is determined whether the pressure plate 3B is opened or closed by the signal from (S6). When the pressure plate 3B is closed to cover the original, the transfer paper size data (Ps) is (A
3) is stored (S7), and the normal copy subroutine is executed according to this size data (S5). In this case, since the pressure plate 3B is closed, reflected light is incident on the exposure device 3 from a position other than the document placement region, so image formation is performed outside the image formation region on the photosensitive drum 1. I don't know.

When it is determined by the signal from the pressure plate opening / closing sensor 20 that the pressure plate 3B is open, the transfer paper size data (Ps) is stored as (A3) (S3).
8). As a result, in the sub-scanning direction of the photoconductor drum 1, the erasing operation is performed up to the end of the maximum image forming area at the timing according to the detection of the transfer paper rear end by the paper length detection sensor 18, and in the main scanning direction. Erase work is not carried out. When it is determined that the pressure plate 3B is open, the drive motor of the transfer belt 5A that kicks the transfer device 5 is driven (S10), and the drive is continued for a predetermined time (T1) (S11), and the time is measured. To be done. When a predetermined time (T1) has elapsed, the drive motor for the transfer belt 5A is stopped (S12, S13). As a result, when an image below the maximum image forming area on the photosensitive drum 1 is formed, if the toner attached to the area corresponding to the difference between the sizes is transferred to the transfer belt 5A, the transferred toner Are completely scraped off by the belt cleaning device 13.

Next, the embodiments of the invention described in claims 2 and 3 will be described with reference to FIGS.

In this embodiment, when the paper is manually fed, it is determined whether the fed different-sized transfer paper is of a fixed size or a fixed size, so that the transfer belt is cleaned by the transfer device. Is changed so that the cleaning of the transfer belt is continued for a predetermined time only when the first transfer paper of different size is fed in the case of the fixed size. 7 and 8, the same processes as those shown in FIG. 6 are given only step numbers and their detailed description is omitted. FIG. 7 is a flow chart showing the operation of the control unit 15. In FIG.
When the pressure plate 3B is opened by the signal from
It is determined whether the size is the standard size (S14). In this case, the paper length sensor 18 is used to determine the transfer paper S0.
The length of the transfer sheet S02 in the sub-scanning direction is detected by the detection time from the leading end to the trailing end of the feeding direction 2 and it is determined whether the detection result corresponds to the standard size. Regardless of the standard size or the non-standard size, the transfer paper size data (P
s) is stored as (A3), and a normal copy subroutine is executed based on this size data (S8,
S9). In the transfer device 5, the drive of the transfer belt 5A in the transfer device 5 is continuously driven for a predetermined time as in the case of the embodiment shown in FIG. 6 (S10 to S13).

In either case of the standard size or the irregular size, the image transfer to the first transfer paper is executed by executing the above steps, but thereafter,
Whether it is continuous copying or not Operation panel 15C
It is determined by the input information from the number setting ten key 15C5 in (S15, S16).

When it is determined that the copying is continuous copying in the standard size, the data (PL) relating to the paper length obtained by the input signal from the paper length detecting sensor 18 is stored (S17), and the standard size is stored. A normal copy subroutine is executed based on the data (PL) (S18). In the copy subroutine in this case, the drive timing of the area where the erasing operation is performed and the transfer belt 5A are set by the standard size data (PL).
By the way, the standard size data is the paper length detection sensor 18
The data (count number) and the length of the transfer sheet S02 in the sub-scanning direction in the standard size are as follows. Detection data PL 420 A3 364 B4 210 A4 182 B5 It is determined in step S16 that continuous copying is performed with an irregular size.
When the determination is made in step 1, the transfer belt 5A is driven for a predetermined time for each image transfer until the transfer of the set number of images is completed.

In the present embodiment, in the case of continuously copying a transfer paper of a fixed size which is more frequently used than a fixed size, the transfer belt is driven for a predetermined time only when the image is first transferred onto the transfer paper. By this, it is possible to prevent the backside of the transfer belt from being contaminated with toner on the transfer sheet.On the other hand, when continuous copying is performed on a transfer sheet of an irregular size, the transfer belt is cleaned every time an image is transferred. Even if the size is not known, it is possible to prevent the back stain of the toner on the succeeding transfer paper at the time of continuous copying.

Next, an embodiment of the invention described in claims 4 and 5 will be described with reference to FIG.

The present embodiment is characterized in that it is possible to prevent the time required for cleaning the transfer belt from being long when the transfer paper by manual feeding is used. Note that in FIG. 9, the same processes as those shown in FIGS. 6 to 8 are given only step numbers, and detailed description thereof will be omitted.

In FIG. 9, in the case of image transfer to the transfer sheet S01 fed from the sheet feeding cassette 11, the same processing as the steps shown in Steps S1 to S5 in FIGS. The presence or absence of the transfer sheet S02 on the manual feed tray 12A is determined by a signal from the paper end sensor 15 located on the tray 12A (S2).
0). In this determination, when the paper end sensor 15 does not detect the transfer sheet S02 on the manual feed tray 12A, the paper end flag (PE) is set (S2).
1) If there is the transfer sheet S02, the paper end flag (PE) is reset (S22). On the other hand, when manual paper feed is selected, the paper end flag (P
By determining E), the presence or absence of the transfer sheet S02 on the manual feed tray 12A is determined (S23). When the paper end flag (PE) is set in step S23, the transfer sheet S is placed on the manual feed tray 12A.
02, it is determined that the transfer paper size data (Ps) is the maximum size (A3) (S7), and if the transfer paper S02 is present, the transfer paper size data (Ps)
s) is stored using the data indexed by the paper length detection sensor 18 (S17).

When it is determined that the pressure plate 3B is opened by the signal from the pressure plate opening / closing sensor 20, (S
6) A normal copy subroutine is executed based on the transfer paper size data set in step S7 or step S17 (S9).

When the processing of step S9 is executed, the presence or absence of the transfer sheet S02 on the manual feed tray 12A is determined by the paper end flag (PE) (S24). In this case, when the paper end flag (PE) is set, it means that there is no transfer sheet S02 on the manual feed tray 12A, and the drive timing of the transfer belt 5A continues for a predetermined time longer than that in the normal copy cycle. The state to be set is set, and the toner transferred onto the transfer belt 5A is scraped off (S10 to S13).

If the paper end flag (PE) is reset in step S24, it is determined whether or not the repeat mode is in accordance with the set number of sheets (S).
15) In the case of the repeat mode, the transfer paper size data (Ps) is updated to the length data (PL) in the sub-scanning direction which is indexed by the paper length detection sensor 18 from the next image transfer. (S17), and a normal copy subroutine is executed based on the length data (S18). When the process of step S18 ends, the presence or absence of the transfer sheet S02 on the manual feed tray 12A is detected by the paper end sensor 15, and the paper end flag (PE) is switched according to the detection result (S20-22).

In this embodiment, when continuous copying is performed by manual paper feeding, only the first transfer paper size data is used for the maximum image forming area, and the transfer paper is used for the next copying. Since the size data uses the data indexed by the paper length detection sensor 15, the time required for cleaning the transfer belt 5A is shortened as compared with the case of targeting the maximum image forming area. be able to.

The present invention has shown an example in which a transfer belt is used as the structure of the above-mentioned contact type transfer device, but the present invention is not limited to this example, and for example, a roller may be used instead of the transfer belt. .

[0059]

As described above, according to the first aspect of the present invention, the transfer fed from the manual paper feeding section is performed when the document pressing member installed on the document placing table is opened. Only when the toner image is transferred to the paper, the transfer belt cleaning is continued for a predetermined time after the toner image is transferred. Therefore, an image forming area smaller than the maximum image forming area is selected. In this case, all the toner transferred to the transfer device side can be completely removed. As a result, it is possible to prevent the toner from being transferred to the back side of the transfer sheet, which is conveyed next, and to prevent the transfer sheet from being stained on the back side.

According to the second to fifth aspects of the present invention, the transfer belt is cleaned every time the toner image is transferred, only when the irregular-sized transfer paper is fed from the manual paper feeding unit and when the size is changed. Therefore, even if a non-standard size transfer paper is used, it is possible to reliably prevent the backside of the transfer paper from being soiled. Moreover, during continuous copying, the cleaning time of the transfer device is set only for the first transfer paper for the maximum image forming area, and from the next time, the time required for cleaning depends on the size of the transfer paper to be fed. Therefore, it is possible to shorten the time required for toner removal by the transfer device.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining the outline of the overall configuration of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic diagram for explaining a configuration of a transfer device and a cleaning device of the transfer device used in the image forming apparatus shown in FIG.

FIG. 3 is a block diagram illustrating a configuration of a control unit used in the image forming apparatus illustrated in FIG.

4A and 4B are views for explaining the configuration of a pressure plate opening / closing sensor used in the control unit shown in FIG. 3, in which FIG.
(B) is an enlarged perspective view of a portion indicated by reference numeral 20 in (A).

5 is a plan view for explaining the configuration of an operation panel that forms an operation unit used in the control unit shown in FIG.

FIG. 6 is a flowchart for explaining the operation of the control unit shown in FIG.

FIG. 7 is a flowchart for explaining another operation of the control unit shown in FIG.

FIG. 8 is a subroutine of the flowchart shown in FIG.

9 is a flowchart for explaining another operation of the control unit shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor drum 3 Exposure device 3A Document placing table 3B Pressure plate serving as a document pressing member 5 Transfer device 5A Transfer belt 11 Paper feeding cassette 12 serving as paper feeding unit 12 Manual paper feeding unit 13 Belt cleaning device 14 Eraser 15 Control unit 15C Operation unit Forming operation panel 15C1 16 Paper end sensor 18 Paper length detection sensor 20 Pressure plate open / close sensor

Claims (5)

[Claims] 1. A toner image carried on a photosensitive member according to the contents of an original placed on an original placing table is transferred onto a transfer sheet onto a transfer sheet using a transfer belt capable of contacting the photosensitive body. In an image forming apparatus having a transfer structure, a paper feed unit that is installed in the main body of the apparatus, accommodates a transfer paper of a predetermined size, and feeds the transfer paper toward the transfer belt; Separately, it is provided in the main body of the apparatus, and can manually feed a transfer paper of a fixed size or an unfixed size including a size different from that of the transfer paper stored in the paper feed unit toward the transfer belt. The paper feed unit, the cleaning member that can come into contact with the transfer belt, and the drive unit for the transfer belt are connected to each other, and the size detection and the document loading of the transfer paper fed from the manual paper feed unit are performed. Installed on a table A control unit capable of detecting the open / closed state of the document pressing member, and the control unit controls the manual paper feeding unit when the document pressing member installed on the document placing table is opened. An image forming apparatus characterized in that cleaning of the transfer belt is continued for a predetermined time after the transfer of the toner image only when the toner image is transferred to the transferred transfer paper. 2. The image forming apparatus according to claim 1, wherein the control unit is capable of determining whether the transfer paper fed from the manual paper feed unit is of a fixed form or an irregular form. Only when the original pressing member is open, if the original is fixed, the transfer belt cleaning is continued for a predetermined time only after the toner image is first transferred onto the transfer paper fed from the manual paper feeding unit. In the case of an irregular shape, the image forming apparatus is characterized in that the transfer belt is continuously cleaned for a predetermined time each time the toner image is transferred onto the transfer paper. 3. The image forming apparatus according to claim 2, wherein the control section moves the transfer sheet detected by a sensor arranged in a feeding path of the transfer sheet fed from the manual sheet feeding section. An image forming apparatus characterized by distinguishing a fixed form and an irregular form based on the length in the direction. 4. The image forming apparatus according to claim 1, wherein the controller is fed from the manual sheet feeder during a time required for transferring a toner image. The image forming apparatus is characterized in that whether the size of the transfer paper is changed or not is determined, and when the size is not changed, the transfer belt is not cleaned every time the toner image is transferred. 5. The image forming apparatus according to claim 4, wherein the controller determines whether or not the size has been changed, based on the presence or absence of a transfer sheet in the manual sheet feeder.