JP3198798B2 - Image forming device - Google Patents

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 for transferring a toner image formed on a photoreceptor, and more particularly, to applying a release material for preventing toner from being offset from a fixing roll or a pressure roll. The present invention relates to an image forming apparatus including a fixing device of a system and using a moving body for sucking and conveying a transfer image or a transfer sheet.

[0002]

2. Description of the Related Art A transfer sheet is electrostatically attracted to an insulative transfer belt or the like running in synchronization with an image forming means and is conveyed to a transfer position of the image forming means. An image forming apparatus for transferring the transfer toner formed on the forming means to a transfer sheet is disclosed in U.S. Pat. No. 25,768.
82, U.S. Pat. No. 3,357,325 and the like. Further, in an image forming apparatus that forms a color image using a plurality of photoconductors, an insulative transfer belt is used as a transfer sheet conveying unit, and as a merit of a method of sequentially transferring a transfer image to a transfer sheet, a toner image is superimposed. In such a case, since the weight of the toner increases, a large amount of transfer charge is required. In this type of image forming apparatus, a corona discharger for electrostatically attracting transfer paper to an insulating transfer belt and a corona discharger for generating a transfer electric field by corona discharge from the back of the insulating transfer belt to transfer a transfer toner image. And an AC corona discharger for removing and removing the transfer paper after the transfer from the belt is completed, and an AC corona discharger for removing the charge from the belt.

On the other hand, it is known that a part of the release agent (oil) supplied to the fixing roll or the pressure roll is transferred to the transfer paper fixed by such a fixing device. The oil transferred to the transfer paper diffuses into the paper fibers between toner particles or through pinholes in a relatively short time. Also, the oil transferred to the paper surface where the toner image does not exist, that is, the oil transferred directly to the paper surface, similarly diffuses into the paper fibers, and has little effect on the operation of the image forming apparatus or the image quality. there were.

However, a color image forming apparatus, particularly a color image forming apparatus that reproduces a large number of colors by superposing three or four color toners, has the following points compared with a conventional single color image forming apparatus. to differ greatly. 1. In order to reproduce a large number of colors by superimposing toner, the toner layer to be fixed is thick. 2. In order to form a color by mixing toners of different colors by fixing, the toner must be sufficiently heated and fluidized. The above point is a condition that the offset phenomenon is likely to occur for the fixing device.

In order to prevent such an offset phenomenon, a fixing device having high releasability is required in a color image forming apparatus. For this purpose, a fixing device that applies a large amount of release agent, that is, silicone oil, as a release layer to a fixing roll coated with a rubber-like elastic material such as silicon rubber is used. Further, from the viewpoint of improving the reliability of the fixing device as the printing speed of the full-color image forming apparatus increases,
It becomes necessary to supply a large amount of oil stably to the roll.
Further, it has been found by measurement that the amount of silicone oil supplied to the transfer paper also depends on the image density. For example, in the case where a blank print on which no image is placed is taken and the amount of oil supplied to the transfer paper is about 15 μl per sheet, the amount of silicone oil supplied to the transfer paper as the image density increases And when the image density reaches 80%, about 20μ per sheet
A liter of silicone oil is supplied. This is considered to be an increase due to the silicone oil soaked in the toner and adhered to the toner surface in addition to the silicone oil supplied to the transfer paper itself.

From the above, when a large amount of silicone oil is supplied to the fixing device, particularly when an image having a high image density such as a photograph or a chart is printed, a large amount of silicone oil is present on the toner in the image portion. become. In the high image density portion, since the toner particles are sufficiently fused and united, the silicone oil passes between the toner particles and remains on the toner surface for a relatively long time without diffusing into the paper fibers. . When the single-sided printing paper in such a state is circulated in the image forming apparatus for double-sided printing, the silicone oil adhering to the paper adheres to the conveyance rolls, the transfer belt, the photosensitive member, etc. of the paper conveyance path. .

On the other hand, when the transfer sheet is jammed, or when the transfer image on the photoreceptor protrudes from the transfer sheet, the toner on the surface of the belt that conveys the transfer sheet protrudes from the surface of the belt. There is a possibility that the toner adheres to the back surface of the subsequent transfer sheet, so that a cleaning means for cleaning the surface of the belt is generally provided. Also,
In an image forming apparatus that forms a color image using a plurality of photoconductors, a positional deviation in the transfer paper feed direction is likely to occur.
No. 263, etc., a registration mark for registration correction is transferred onto a transfer belt,
The position of the color is read by a CCD sensor or the like, and the position of each color is automatically adjusted.
No. 9275, JP-A-63-279276, JP-A-61-53756, etc., transfer a registration mark for registration correction, read the position of the registration mark with a photo sensor or the like, and at the same time, read out the position of the photo sensor. A method of providing a batch image for controlling the toner density of each color according to the output is disclosed, and this mark is finally cleaned.

Various cleaning means for cleaning the toner transferred onto the transfer belt as described above have been proposed, including blades, fur brushes, webs, and the like, and combinations thereof. The blade method was most suitable. When automatic double-sided printing is performed with a full-color image forming apparatus, silicone oil adhering to the image surface (first surface) of the transfer paper is transferred to the transfer belt, and silicon oil adhering to the back surface (second surface) is transferred to the photoconductor. . Furthermore, when the paper is conveyed and attracted to the transfer belt to transfer the image on the second side to the paper during double-sided printing, the silicone oil attached to the first side of the paper placed on the belt is transferred to the transfer belt. . As a result,
The coefficient of friction between the cleaning blade and the transfer belt greatly fluctuates in an area where silicone oil is adhered on the transfer belt and in other areas.

That is, the coefficient of friction between the cleaning blade and the transfer belt in the area (portion) where the silicone oil is attached becomes extremely small, but the cleaning blade and the transfer belt in the area where the silicone oil is not attached. The friction coefficient was large, and the sticking phenomenon of the cleaning blade occurred due to the fluctuation of the friction coefficient. As described above, a registration mark for registration correction, a patch image for density control, untransferred toner at the time of paper jam, and the like are placed on the transfer belt, and the transfer belt is cleaned with a cleaning blade of a transfer belt cleaner. If the cleaning blade is vibrating due to such an extreme stick-slip phenomenon, the toner on the belt does not come into contact with the transfer belt, and the toner on the belt passes through the cleaning blade, and toner is formed on the belt. The job proceeds to the next job while remaining. Residual toner due to defective cleaning on the transfer belt was transferred to the back surface of the transfer paper in the suction area and the transfer area, and the back surface of the paper was stained.

[0010]

The cleaning failure of the transfer belt caused by the double-sided printing often appears more remarkably after the completion of the double-sided printing and after the transition to the normal single-sided printing than during the double-sided printing job. . The distortion of the cleaning blade of the transfer belt was measured by a distortion gauge. FIG. 12 shows the measurement results. The operation area for double-sided printing is DA, and the operation area for single-sided printing is SA. As shown in the results, if the printing operation is shifted from the double-sided printing area DA to the single-sided printing area SA and one-sided printing is continued for a while, the fluctuation of the distortion of the cleaning blade is further increased. This is because the stick slip phenomenon is accelerating. This phenomenon is considered to be a result of the silicone oil adhering to the transfer belt being reversely transferred to the paper at the time of one-sided printing after the transfer to the one-sided printing, and the silicon oil on the transfer belt being gradually reduced.

As described above, the amount of the silicon oil on the transfer belt causes the fluctuation of the distortion of the cleaning blade. As the one-sided printing is further continued, the fluctuation of the distortion of the cleaning blade gradually decreases and returns to the original state. As described above, when the degree of occurrence of the cleaning failure is small, the cleaning failure may disappear by continuing the single-sided printing. However, when the operation shifts to double-sided printing again, the above phenomenon is repeated. Also, while repeating only double-sided printing,
It was also confirmed that the silicon oil adhered to the entire area on the transfer belt, and conversely, the fluctuation of the distortion of the cleaning blade was reduced, and the cleaning failure was hardly generated. This is a fact supporting the fact that the above-mentioned fluctuation of the distortion of the cleaning blade causes cleaning failure.

The present invention has been made on the basis of such a background, and when the second side is printed on the back side of the sheet in the double-sided printing, the release agent adhering to the image side (the first side) of the transfer sheet is transferred to the surface of the moving body. It is an object of the present invention to minimize the fluctuation of distortion in a cleaning blade of a cleaning member of a moving body caused by the transfer to the above, to prevent defective cleaning, and to obtain stable image quality maintenance.

[0013]

According to the present invention, there is provided an image forming apparatus having cleaning means for cleaning a transfer image on a moving body, which holds a toner image or a transfer sheet on which the toner image is transferred. The moving body to be moved is divided into a plurality of (odd and even) areas in which the toner image or the transfer paper is arranged based on information such as the position detection signal of the moving body, the image size, the paper size, and the like. The first surface toner image or transfer sheet is arranged during one rotation of the moving body, and at least a part of the second surface toner image or transfer sheet is arranged during the other rotation. Basically, there is provided control means for controlling the arrangement of the divided areas.

Further, when the double-sided print mode is set, the control means sets the second image in the divided area adjacent to the divided area where the placement of the toner image for the first side or the transfer sheet is started.
A control for arranging the toner image or transfer paper for the face, a control for sequentially displacing the arrangement position of the first toner image or transfer paper to be arranged on the moving body for each job, or
If the moving object has an even number of divided areas, the job in which the first toner image or the transfer paper is arranged in the divided area from the even number of divided areas on the moving object and the first toner on the moving object are arranged. A configuration is provided in which a job in which an image or a transfer sheet is arranged in a divided region from an odd-numbered divided region is alternately selected for each job.

[0015]

In the double-sided print mode, the transfer paper printed on the first side, passed through the fixing device and coated with silicone oil on the surface, is copied on the second side during the previous rotation of the moving body during the copying of the second side. Is placed in the area where the paper is placed, so the silicone oil is evenly transferred to the surface of the moving body,
The variation in friction due to the area between the moving body and the cleaning means is minimized.

[0016]

An embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a full-color image forming apparatus to which a transfer device according to one embodiment of the present invention is applied. The full-color image forming apparatus includes image carriers (photosensitive drums) 2Y, 2M, 2C, and 2K rotatably supported on a rotating shaft, and an image forming unit is arranged on an outer peripheral portion of each image carrier. The image forming means may be any means, but the image forming means shown in this embodiment is separated into primary chargers 3Y, 3M, 3C, and 3K which uniformly charge the surface of the photosensitive drum to, for example, -500 to 800V. Exposure means for irradiating the light image or a light image corresponding thereto to form an electrostatic latent image on the photosensitive drums 2Y, 2M, 2C, 2K, for example, an exposure means (not shown) comprising a laser beam exposure device or the like And the photosensitive drums 2Y, 2M, 2C,
Developing devices 5Y, 5M for visualizing an electrostatic latent image on 2K,
5C and 5K. Developing devices 5Y, 5M, 5C,
5K stores a developer such as toner of four colors of yellow, cyan, magenta and black, and a laser beam is applied to a portion of the uniformly charged photosensitive drum on which an electrostatic latent image is formed. Is selected such that the developing bias is attached.

The visible image (toner image) developed on the photosensitive drum is formed by a drive shaft 9 and shafts 10-1
2, the image is transferred onto the transfer paper 70 conveyed by the transfer belt conveying device that moves in the direction of arrow A. The transfer paper 70 supplied from the paper feeding device is supplied to the suction corona discharger 14.
, And are sequentially conveyed to transfer positions provided opposite to the respective image carriers. On the opposite side of the transfer belt 7 is a grounded paper suction roll, which injects electric charge into the transfer paper 70 to attract the transfer material (paper) to the transfer belt. In the transfer device, the suction corona discharger 14 and the transfer corona discharger 8Y, 8M, 8
C and 8K are different voltages (for example, +4.2 KV-
12.0 KV), and the transfer current is +50 μm.
A to +2000 μA.

After the transfer is completed, the transfer paper 70 is separated from the corona discharger 20 to which a DC bias of AC oscillation for weakening the electrostatic attraction to the transfer belt 7 can be applied and an insulating member such as resin. It is separated from the transfer belt 7 by the claw 21 and guided to the fixing device 100.

After the transfer belt 70 has been peeled off from the transfer paper 70, the corona discharger 23 for discharging the inner belt and the outer belt for discharging the belt are provided so as to sandwich the transfer belt between the most downstream transfer step and the most upstream transfer step of the transfer step. Corona discharger 2
4 removes the charge. The corona discharger for belt neutralization is an AC corona discharger to which a DC bias of AC oscillation can be applied similarly to the peeling means 20. The surface of the transfer belt 7 from which the charge has been removed is cleaned by the transfer belt cleaning means, and the transfer belt 7 enters a new round.

A cleaning means for the transfer belt is provided downstream of the corona dischargers 23 and 24 for removing charges. A registration mark for correcting registration, a toner image patch for controlling density, Untransferred toner and the like at the time of paper jam are removed. The transfer belt cleaning means mainly includes a cleaning brush 25 as a cleaning auxiliary means, a cleaning blade 26, a collected toner box (not shown) for storing the cleaned toner, and the like.

As shown in FIG. 3, the transfer belt 7 is made of a highly insulating material such as a polyethylene terephthalate (PET) film, a polyvinylidene fluoride resin film, a polyester film, a polycarbonate film, and a polyetheretherketone film. After this is cut to a predetermined size, the both ends are formed, for example, by ultrasonic welding to form a joint 71, which is an endless belt body, on which transfer paper is placed and transported. The transfer belt of the full-color image forming apparatus in this embodiment has, for example, a thickness of 50 to 50 mm.
A polyethylene terephthalate film having a volume resistivity of 200 μm and a volume resistivity of 10 ¹⁶ to 10 ²⁰ Ωcm is used. The diameter of the photosensitive drums 2Y, 2M, 2C, 2K is 84 m.
m, the length of the transfer belt is 1920 mm, and the distance between the axes of the photosensitive drums, that is, the distance between each transfer point is 196 mm.

Next, the flow of the transfer paper 70 in the double-sided print mode in the image forming apparatus will be described. The paper transport system that transports the paper 70 includes a duplex transport unit 210 that transports the paper during duplex printing, and a supply-side transport path 220 that guides the paper 70 from the paper feed tray 300 to the transfer belt 7.
And a sheet reversing conveyance path 230 that guides the sheet 70 that has passed through the fixing device 100 to the two-sided exclusive conveyance section 210, and a discharge side conveyance path 240 that guides the sheet on which double-sided printing has been completed to the discharge tray.

The paper 70 according to the transport path system is sent from the paper feed trays 300, 305, and 310 of various sizes to the supply-side transport path 220 by the feed roll 301, the transport roll 302, and the like. The sheet 70 traveling on the supply conveyance path 220 by the conveyance roller 221 is once positioned by the registration gate 225 and then supplied onto the transfer belt 7 at a predetermined timing. The paper 70 is electrostatically attracted to the transfer belt 7, moves with the progress of the transfer belt 7, and the toner images of the respective colors are sequentially transferred from the four photoconductors 2Y, 2M, 2C, 2K to the surface thereof. The paper 70 separated from the transfer belt 7 by the separation claw 21 is heated and fixed by the fixing device 100 with the toner image. At this time, the toner image is
A large amount of a release agent such as silicone oil is applied to the surface of the paper in order to prevent offsetting to the paper roll 05 or the pressure roll 110.

In the case of single-sided printing, the paper 70 is provided at the intersection of the carry-out side conveyance path 240 and the sheet reversal conveyance path 230, and a switching gate 235 for selecting any one of the conveyance paths is switched to the carry-out side conveyance path 240. Conveyance roll 241
Is discharged through the unloading-side transport path 240. In the case of double-sided printing, the switching gate 235 is switched to the sheet reversing conveyance path 230. Then, the sheet 70 is sent to the sheet reversing conveyance path 230, and the sheet passing through the conveyance path is turned upside down and sent to the double-sided exclusive conveyance section 210. This sheet is advanced to the upstream side of the image forming apparatus by the transport rolls 221, sent again to the transfer belt 7, and the back side (second
The toner image is transferred to the surface. This full-color image forming apparatus has an image memory for a maximum of two sheets of paper. The image reading apparatus first stores the image of the first side of the original, then stores the image of the second side of the original, and then performs the image forming operation. Enter.

Here, the supply of the sheet onto the transfer belt 7 will be described. In the one-sided printing mode, the transfer paper 70 is supplied continuously in the belt traveling direction on the transfer belt 7. In the double-sided print mode, after the first transfer sheet 70 is supplied, the second sheet is supplied at an interval of one sheet (size). After intermittently supplying the first side of the transfer paper while the transfer belt 7 makes one rotation, the second side intermittently supplies the first side of the transfer paper and printing the first side on the provided space. Then, the paper circulating in the apparatus is supplied, and the second side of the document is printed. With this configuration, the image forming apparatus shown in this embodiment can continuously perform automatic double-sided printing without having a dedicated double-sided stack tray. Hereinafter, this type of device will be referred to as a trayless device.

In addition, as shown in FIG. 2, a double-sided stack tray 350 for temporarily storing sheets on which printing on the first side has been provided is provided downstream of the sheet reversing conveyance path 230, and sheets from the double-sided exclusive stack tray 350 are provided. A feed roll 351 for sending to the both-side dedicated transfer unit 210 was provided.
There is an image forming apparatus provided with a so-called double-sided stack tray 350. In this case, all the sheets on which printing on the first side has been completed are temporarily stored in the intermediate tray 350, and when the preparation for the second side is completed, the stack tray 350 for exclusive use on both sides is used.
, And the sheet is continuously fed, and the transfer of the second side is performed. Hereinafter, this type of device is referred to as a stack tray equipped device. This image forming apparatus does not need to have an image memory for a maximum of two sheet sizes. Other configurations are the same as those of the trayless device.

In this embodiment, in addition to the above configuration, a reflection type optical sensor 40 including a light emitting section and a light detecting section is provided as a joint position detecting means of the transfer belt 7. Since the seam 71 formed on the transfer belt 7 is ultrasonically welded, the dielectric constant of this seam portion is different from the other portions of the belt. As a result, the amount of charge applied to the transfer paper at the time of the transfer is different from that of the other portions only at the seam portion, so that the density of the transferred image changes only at the seam portion.

To avoid this problem, Japanese Patent Application Laid-Open No. Sho 62-2
Japanese Patent No. 69160 discloses a method in which a hole or mark 75 is provided at a fixed position from the joint of the transfer belt.
And a method of recognizing the position of the joint 71 of the transfer belt, and a pulse generator that generates a pulse signal each time the transfer belt moves by a predetermined amount, and a counter that counts the pulse signal, A method of distributing the counted pulse signals equally to the number of image areas during one rotation of the transfer belt and determining the image area (referred to as a panel division method) has been proposed.

Therefore, in this embodiment, a plurality of image areas (panels) are formed by distributing the transfer belt at equal intervals avoiding seams for each size of transfer paper by this panel dividing method, and one area (hereinafter referred to as a panel). ), One copy sheet is placed on the transfer belt, and an integer number of transfer sheets are always arranged around the transfer belt. The transfer sheet is sent out at a timing avoiding the seam so that the gap between the sheets becomes constant. Is controlled. Further, the image forming apparatus generates a pitch reset signal according to the number of panels when the number of divided panels is determined in accordance with the above-described panel division of the transfer belt 7.
The pitch reset signal is a signal that is synchronized with the number of divided panels that occur periodically while a sheet of the same size is being conveyed. The pitch reset signal detects the stop position of the transfer belt 7 at the end of the job, and starts the next image forming operation with the shortest rise time regardless of the position of the joint 71 of the transfer belt 7. For example, when the length of the transfer belt is 1920 mm and the number of divided panels is 8, if the process speed is 160 mm / sec, a pitch reset signal for each panel is generated every 1.5 seconds (1920/8160).

Here, as means for increasing the discharge time of the print of the first side, the seam of the transfer belt can be ignored and the seam can be used as an effective image area. The dielectric constant is different due to the thicker part, causing abnormalities in the transferred image, and the toner remaining on the step part of the joint passes through the cleaning blade and is eventually transferred to the back side of the paper sent over the joint. This is not preferable because it causes a problem of being lost. Therefore, when the panel is divided as shown in the table, the joint of the transfer belt is controlled to be located almost at the center of the dimension of the gap between the sheets on the transfer belt. The panel dividing method as described above has the highest productivity without causing a defect in image quality.

Next, the division of the transfer belt 7 into panels and the supply of the transfer paper 70 to the transfer belt 7 during double-sided printing will be described. The transfer belt 7 shown in FIGS. 4 to 8 is illustrated in a state in which the transfer belt 7 having an endless shape by the joint 71 is expanded into a plate shape for convenience, and the joint 71 has both ends. In the case of even-numbered panel division, the entire length of the transfer belt 7 is evenly divided, for example, into eight, and panels 1 to 8 are obtained. Then, a pulse signal 4 for each panel
5 is transmitted. In the case of odd division, the total length of the transfer belt is divided into odd numbers, and a pulse signal is transmitted for each panel. The transfer paper is supplied onto the transfer belt 7 configured as described above. Here, the paper printed on the first side (front side) of the paper is represented by S, and the paper printed on the second side (back side) is represented by D.

Supply of Transfer Paper in the Case of Trayless Device (1) Even Panel Dividing ... See FIGS. 4 and 5 FIGS. 4 and 5 show an image forming apparatus having a two-sided printing mechanism using a trayless device. The state of supply of the first and second sheets on the transfer belt 7 divided into eight panels is shown. Printing conditions, paper used;
A4 size, direction: horizontal placement, number of prints: 10
Sheet.

First lap First sheets S1, S2, S3, and S4 on the first side are supplied from the sheet supply tray to the positions of panels 1, 3, 5, and 7 which are odd panels, and the first side of the document is copied. . At this time, the even panels, panel 2, panel 4, panel 6,
Panel 8 is skipped.

Second lap The sheets S1, S2, S3, and S4 printed on the first sheet of paper in the first lap are located at the positions of panels 2, panel 4, panel 6, and panel 8, which are the even panels skipped in the first lap. Is circulated in the apparatus and turned over, and paper D1 for printing the second side is provided.
D2, D3, and D5 are supplied from a double-sided dedicated conveyance path. The second side of the document is transferred to the sheets D1, D2, D3, and D5. On the other hand, at the positions of the panels 1, 3, 5, and 7 which are odd panels, new sheets S5 and
S6, S7, and S8 are supplied from the paper tray, and the first side of the document is printed.

Third cycle Since the last sheet supply in the second cycle is the sheet D4 on the second side, a new sheet S9 is supplied from the sheet tray to the position of the panel 1 in the third cycle. Then, the set number of last sheets S10 are supplied to the position of the panel 3, and the first side of the document is printed. The positions of panels 5 and 7 are skipped. Panel 2, Panel 4, Panel 6, which are even panels
The sheets S5, S6, S7, and S8 printed on the first side of the sheet in the second round circulate in the apparatus at the position of the panel 8 and are reversed, and are supplied as sheets D5, D6, D7, and D8 from the duplex path. Then, the second side of the document is transferred.

Fourth lap Since the last paper supply in the third lap is the second copy paper, new paper is supplied to the position of the panel 1 in the fourth lap. Since the supply of 10 sheets has been completed, panels 1 and 3 are skipped. Then, at the positions of panel 2 and panel 4, which are even panels,
Papers S9 and S10 printed on the first side of paper in the third lap
Is circulated in the apparatus and is inverted, and is supplied as a sheet D9 and D10 from a double-sided exclusive conveyance path, and the second side of the document is transferred.

As described above, the double-sided printing of ten sheets of paper is completed after the transfer belt 7 makes four revolutions. In this embodiment, the sheet is supplied from the position of the panel 1 of the belt 7, but the first sheet supply panel may be at any position of the panel 1 to the panel 8. That is, if the first sheet S is supplied from the odd panel (or even panel), the second sheet D
Is always an even (or odd) panel. Then, the silicone oil applied to the paper while passing through the fixing device 100 is transferred from the paper to a transfer belt or a photoconductor. At this time, the printed paper to which the oil has been applied after passing through the fixing device supplied on the belt 7 is supplied every other panel, so that the silicone oil applied to the paper always remains on the belt 7 every other panel. Will be supplied.

As described above, in the example in which the belt 7 is divided into even-numbered panels, the panel on which the silicone oil is adhered and the panel on which the silicone oil is not always determined on the transfer belt. That is, in the schematic diagram shown in FIG. 4, in the belt portion at the position of the odd-numbered panel (1, 3, 5, 7), while printing is completed, in this example, new paper is always arranged in all four turns, and the even-numbered panel ( Printed paper is arranged in the belt portion at positions 2, 4, 6, 8). As a result, the coefficient of friction between the transfer belt and the cleaning blade greatly fluctuates for each panel between the portion where the oil is transferred to the belt 7 and the portion where the oil is not transferred, which causes a cleaning failure.

In order to prevent this, in the next double-sided print job, the first sheet S1 is supplied from the position of the panel 2, which is an even-numbered panel (see FIG. 5). In this way, in the first double-sided print job, new paper S is always supplied to the positions of panels 2, 4, 6, and 8 which are even-numbered panels to which silicon oil has always adhered. In the first double-sided print job, the sheets printed on the first side are always in the positions of panels 1, 3, 5, and 7, which are odd panels, to which the silicone oil did not always adhere. D is supplied. Further, in the next double-sided print job, the first sheet S is supplied again from the position of the panel 1 which is an odd-numbered panel.

This control method will be described with reference to a control flow shown in FIG. When the duplex print mode is set in step 200, when the previous duplex print mode is set in step 210, it is determined whether the supply of the first sheet is an odd-numbered panel. At the previous time, in the case of feeding paper from the odd-numbered panel, new paper is fed from the paper feed tray to the even-numbered panel in step 211. When one rotation of the transfer belt is completed in step 212, new paper is continuously supplied from the paper feed tray to the even-numbered panel in step 213, and the single-sided paper, which is a sheet from the double-sided conveyance unit, is printed on the odd-numbered panel. The paper that is turned around during the circulation is supplied. When the number of sheets supplied from the sheet feeding tray reaches the set number in step 214, the process proceeds to step 215, where the sheets from the double-sided exclusive conveyance unit are supplied to the odd-numbered panel, and the process ends in step 216. If the determination in step 210 is NO, the process proceeds to step 220, and new paper is supplied from the paper feed tray to the odd-numbered panel until one rotation is determined to be completed in step 211. When it is determined that one rotation has been completed, the paper from the odd-numbered panel paper feed tray is supplied in step 222 until the set number of prints is counted in step 223, and the inverted paper is supplied from the double-sided exclusive conveyance unit to the even-numbered panel. I do. When the set number is counted, step 2
Proceeding to 24, the paper from the double-sided exclusive conveyance unit is supplied to the even-numbered panel, and the process ends in step 225.

In this manner, the supply panel for the first sheet S at the start of the job is changed for each job and the double-sided print job is repeated, so that the second sheet D is supplied to all the panels of the transfer belt 7. As a result, the silicone oil adheres to all the panels of the transfer belt. As a result, the width of the friction coefficient of the cleaning blade 26 with respect to the transfer belt 7 is reduced, and cleaning failure is less likely to occur.

In the embodiment in which the transfer belt 7 is divided into an even number of panels as described above, the paper S is supplied from the position of the panel 1 in the first double-sided print job and from the position of the panel 2 in the subsequent double-sided print job. However, if the paper S is supplied from any of the odd-numbered panels (even panels) in the first double-sided print job, the paper S is supplied from any of the even-numbered panels (odd-numbered panels) in the subsequent double-sided print job. I just need. At this time, the pitch reset signal 45 is used for the recognition method of each panel. Therefore, as long as the same sheet size is used continuously, the image forming apparatus always recognizes which panel is an odd-numbered panel (even-numbered panel) by the pitch reset signal. The position of the S supply panel can be arbitrarily selected.

(2) Odd panel division: see FIG. 6 FIG. 6 shows a transfer belt 7 divided into seven panels having a joint 71 at the time of two-sided printing in an image forming apparatus having a two-sided printing mechanism using a trayless apparatus. One up
The state of supply of the first and second sheets is shown. Printing conditions Paper used: A4 size, direction: horizontal placement, number of prints: 10 sheets.

First cycle The sheets S1, S2, S3 of the first side are supplied from the sheet tray to the positions of the panels 2, 4, and 6, which are the even panels. At this time, the panels 1, 3, 5, and 7 which are odd panels are skipped.

Second lap A new sheet S4 is placed at the positions of panels 1, 3, 5, and 7 which are the odd panels skipped in the first lap.
S5, S6, and S7 are supplied from the paper tray, and the first side of the document is copied. Sheets S1, S2, and S3 printed on the first side of the sheet in the first cycle circulate in the apparatus and are inverted, and are turned into sheets D1, D2, and D3 from the conveyance path dedicated to both sides to the panel 2,
It is supplied to panels 4 and 6. Paper D1, D2, D
The second side of the original is transferred to the third.

Third lap A new sheet S is placed at the positions of the panels 2, 4, and 6.
8, S9 and S10 are supplied from the paper tray. The sheet S printed on the first side of the sheet in the second round at the positions of the panels 1, 3, 5, and 7 which are odd panels.
4, S5, S6, and S7 are circulated in the apparatus and inverted, and are supplied as papers D4, D5, D6, and D7 from the double-sided exclusive conveyance path, and the second side of the original is transferred.

Fourth lap Since double-sided printing has been completed up to the seventh sheet in the third lap, printing is performed on the first sheet of paper in the third lap in the positions of panels 2, 4, and 6 which are even-numbered panels. Paper S
8, S9 and S10 are circulated in the apparatus and inverted, and the paper D
8, D9, D10 are supplied from the double-sided exclusive conveyance path,
The second side of the document is transferred.

FIG. 6 is a schematic diagram showing this state.
In the belt portion at the odd panel (1, 3, 5, 7) position, a new sheet and a printed sheet are arranged every one lap, and the belt portion at the even panel (2, 4, 6, 6) position is also new every lap. Paper and printed paper are placed. As described above, the sheet supply operation is the same as the case of the even-numbered panel division, except that the number of panel divisions of the belt 7 is an odd number, and the transfer sheet 1 is alternately placed at all panel positions in the double-sided print job.
Since the surface and the second surface are supplied, no matter where the first sheet S1 of the first surface is supplied to any panel position, the silicon oil is automatically attached to all the panels as the belt 7 rotates.

Here, the distortion of the cleaning blade of the transfer belt cleaner was measured by a distortion gauge. FIG. 10A shows the measurement results. On the Nth lap, the second sheet was supplied every other panel. Since the amount of oil adhering to each panel changes, the width of the friction coefficient of the cleaning blade is large. Next, in the (N + 1) th week, the sheet on the second side was supplied to the panel on which the first side was arranged in the Nth round. Since oil adheres alternately to adjacent panels, the width of the friction coefficient of the cleaning blade becomes smaller. From this measurement result, it can be seen that the oil adheres to the entire belt by placing the first and second sheets on each panel. Note that this measurement is a measurement result when the gap between the sheets supplied for each of the panels is always at a constant position, and a portion having a high friction coefficient indicated by a portion A in the drawing does not always have the sheet placed thereon. This corresponds to a place where the coefficient of friction is high in the portion. Further, by removing a portion having a high friction coefficient of the portion A, as shown in FIG. 10B, oil can be applied to the entire surface of the belt, and the friction coefficient can be suppressed to a low range. For example, to apply oil to the entire surface of the belt, it is achieved by shifting the paper feeding position and the image writing position for each job within a range that does not join the belt with respect to the panel position determined by the paper size. .

As described above, in the case of the trayless image forming apparatus, when the belt 7 is divided into an odd number, the productivity of double-sided printing slightly decreases depending on the paper size, but stable transfer can be performed without any special control. It is possible to ensure the cleaning property of the belt.

Apparatus equipped with a stack tray for both sides only . See FIGS. 7 and 8. The transfer belt 7 is divided into eight panels. The transfer sheet is A4 size placed horizontally, for example, the number of prints is set to 5, and the supply state of the first and second sheets on the transfer belt 7 during double-sided printing will be described.

First cycle Transfer sheets S1 and S from a sheet feed tray on transfer belt 7
2, S3, S4, and S5 are sequentially supplied to panel 1, panel 2, panel 3, panel 4, and panel 5, respectively. The first side of the document is printed and stacked on the stack tray 350 for both sides.

(N + 1) lap When the preparation for the second side is completed, the stack tray 3
The sheet is fed from the panel 50 and supplied to the panel 1, the panel 2, the panel 3, the panel 4, and the panel 5, and the transfer of the second side of the document is performed on the second side of the sheet. For example, assuming that the number of prints is 20 on an eight-divided transfer belt, the copy of the first surface is completed in three rounds, and the copy of the second surface is started in the fourth round.
In this case, it is not necessary to change the panel division of the transfer belt between the single-sided print mode and the double-sided print mode. Further, in FIG. 8, the first sheet supply panel at the time of printing the first side and the second side is set to the same panel position.
It is not necessary that the panel used for the first side print and the panel used for the second side print coincide. In this case, when the two-sided print job is continuous, the supply panel position of the first sheet of the second side print is appropriately shifted for each job as shown in FIG.
It is also possible to appropriately select a panel position to be shifted according to the number of prints per job. In this way, the printed paper on the first side, that is, the transfer paper on the second side, is supplied to many areas, and the variation in the coefficient of friction between the transfer belt and the cleaning blade caused by the silicone oil is reduced as much as possible. Can be prevented.

Although the embodiment has been described above in which the moving body is an endless transfer belt made of an insulating film that sucks and conveys transfer paper, in the present invention, the moving body is an insulating film that sucks and conveys transfer paper. The operation and effect can be applied to a cylindrical transfer drum made of a film. Further, even if the moving body is an intermediate transfer body that moves while holding the transferred image, the operation and effect can be applied.

FIG. 11 shows an embodiment in which the movable body is an endless photosensitive belt for holding a transferred image. When the moving body is the photoreceptor belt 500, the sheet 700 on which the toner image has been transferred once for the duplex printing is circulated in the image forming apparatus along the sheet conveying path, and the fixing device 1
The silicone oil applied to the paper at 000
It adheres to 0. If the belt 500 is divided into panels and printing is repeatedly performed at positions of the same size, a difference occurs between the position of the image forming panel and the position of the non-image forming panel due to the presence or absence of silicon oil. As a result, poor cleaning of the photoreceptor and non-uniform image density have occurred. In this case, the same problem can be solved by applying the present invention.

[0056]

As described above, the image forming apparatus of the present invention supplies the printed paper on the first side, that is, the transfer paper on the second side, to almost the entire area of the transfer belt, and causes the transfer of the paper on the second side. Variations in the coefficient of friction between the transfer belt and the cleaning means can be minimized to prevent problems in image quality and toner contamination on the back surface of the transfer paper.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the configuration of a trayless image forming apparatus.

FIG. 2 is an explanatory diagram of a configuration of an image forming apparatus equipped with a stack tray dedicated to both sides.

FIG. 3 is a perspective view of a moving body (transfer belt).

FIG. 4 is a schematic diagram of a transfer belt.

FIG. 5 is a schematic diagram of a transfer belt.

FIG. 6 is a schematic diagram of a transfer belt.

FIG. 7 is a schematic diagram of a transfer belt.

FIG. 8 is a schematic diagram of a transfer belt.

FIG. 9 is a control flow of a double-sided print mode by dividing an even panel.

FIG. 10 shows measurement results of strain gauge.

FIG. 11 is an explanatory diagram of a configuration of an image forming apparatus including an endless photosensitive belt.

FIG. 12 shows a measurement result of a strain gauge by a conventional device.

[Explanation of symbols]

2 (Y, M, C, K) image carrier, 3 (Y, M, C,
K) charger, 5 (Y, M, C, K) developing device,
7 moving body (transfer belt), 9 drive shaft, 26 cleaning blade, 70 transfer paper, 71 joint, 100 fixing device, 210 double-sided exclusive conveyance section, 220 supply conveyance path, 230 paper inversion conveyance path,
240 discharge side conveyance path, 300 paper feed tray, S
First side of transfer paper, D Second side of transfer paper.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Satoru Torimaru 2274 Hongo, Ebina-shi, Kanagawa Fuji Xerox Co., Ltd. (56) References JP-A-4-204862 (JP, A) (58) Fields investigated ( Int.Cl. ⁷ , DB name) G03G 21/00 370-540 G03G 21/14 G03G 15/00 106 G03G 21/10-21/12 G03G 15/16-15/16 103

Claims (5)

(57) [Claims] 1. A toner image or a transfer of the toner image.
Moving body holding and holding the transfer paper to be transferred;
A paper feed tray that feeds the paper to the toner image transfer
Fixing unit for fixing toner image transferred to transfer paper
Through the fuser when the duplex print mode is set.
Turn over the transfer paper
Reversal feeding alternately with the transfer paper sent to the transfer site
Conveying means and cleaning for cleaning the surface of the moving body
Means, and the peripheral length of the moving body is set to an integer number of transfer sheets.
To form or transfer a toner image
In an image forming apparatus configured to perform image capturing, a job in a double-sided print mode in which the number of the divided areas is an even number is described.
If the toner images are continuous, the first toner image or transfer paper
Job starting from the even-numbered divided area on the moving object
And the job starting from the odd-numbered divided area
An image forming apparatus characterized in that the image formation is performed. 2. A toner image or a transfer of the toner image.
Moving body holding and holding the transfer paper to be transferred;
A paper feed tray that feeds the paper to the toner image transfer
Fixing unit for fixing toner image transferred to transfer paper
Through the fuser when the duplex print mode is set.
Reverse the transfer paper and store it in the transfer section.
Stack tray and the surface of the moving object
Cleaning means for cleaning, the circumference of the moving body
Is divided into divided areas corresponding to an integer number of
Image formation configured to form or transfer a toner image
If the device is in continuous duplex mode jobs, the first
Area on the moving body where the toner image or transfer paper is placed
Image type characterized in that the image is shifted sequentially for each job
Equipment. 3. A toner image or a transfer of the toner image.
Moving body holding and holding the transfer paper to be transferred;
A paper feed tray that feeds the paper to the toner image transfer
Fixing unit for fixing toner image transferred to transfer paper
Through the fuser when the duplex print mode is set.
Turn over the transfer paper
Reversal feeding alternately with the transfer paper sent to the transfer site
Conveying means and cleaning for cleaning the surface of the moving body
Means, and the peripheral length of the moving body is set to an integer number of transfer sheets.
To form or transfer a toner image
In an image forming apparatus configured to take a picture, the moving body is always divided into an odd number of divided areas.
An image forming apparatus. 4. The moving body sucks and conveys a transfer sheet.
It is an endless transfer belt made of insulating film.
The image forming apparatus according to claim 1, wherein
Place. 5. The moving body moves while holding a transferred image.
4. An intermediate transfer member according to claim 1, wherein
An image forming apparatus according to any one of the above.