JP2009163051A - Image forming apparatus and tandem type image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus forming a good quality image without causing an image failure. <P>SOLUTION: A transfer means includes a transfer member 9, a charging means 10, a destaticization means 11 and a material cleaning means 12, and further includes a contact/separation means for having the transfer member 9 abutted on or separated from an image carrier 1 through a recording medium 16 and a rotating driving means for rotating the transfer member 9 in a direction same as the transported direction of the recording medium 16. The transfer member rotating driving means is linked with an image carrier rotating driving means. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus, and more particularly to an image forming apparatus capable of forming a high-quality image without image defects even when an image is formed on rough paper or wrinkled paper.

  Conventionally, continuous paper printers were often used for computer output printing on forms, but recently they have been used for high-speed variable information printing, and for multi-purpose printing such as direct mail, invoices, manuals, and books. Has come to be used. Along with the expansion of applications used, it is necessary to use various types of webs from thin paper to thick paper and web types from fine paper to rough paper.

  On the other hand, from the viewpoint of resource saving, tandem operation is performed using two continuous paper printers, the first side is printed on the first page, and then the second side is printed on the second side by reversing the web side. As a result, the need for duplex printing is increasing. When dealing with such versatility, the transfer performance of the transfer device is particularly important in order to obtain image quality free from image defects.

  However, in general, in the case of tandem printing, the web is damaged by heat at the first fixing, resulting in unevenness due to heat shrinkage, and the adhesion between the web and the photosensitive drum surface is poor in the second transfer portion. There is a problem that image defects due to transfer defects are likely to occur in the recessed area of the web surface.

  FIG. 8 is a conceptual diagram of a tandem printing method capable of duplex printing on continuous paper. A first continuous paper printer P1 that forms an image 30a on the first surface of the continuous web 16 and a second continuous paper printer P2 that forms an image 30b on the second surface are provided.

  The continuous paper printers P1 and P2 perform printing by conveying perforated box paper or perforated roll paper at a high speed (for example, 0.5 to 2 m / sec). Unlike the cut paper, the web 16 forms a continuous web with no breaks.

  The continuous web 16 is printed on the image 30a by the first printer P1 having an image forming unit such as the photoreceptor 1a or the developing device 4a, and then the web 16 is reversed by the turn bar T, and further the photoreceptor 1b and the developing device 4b. The image 30b is printed on the back surface by the second printer P2 having an image forming unit such as.

  When images are printed on both sides of the web 16 in this way, for example, a second unit is placed on the back surface of the web portion stopped in the B portion area (see FIG. 8) where the fixing portion for fixing the first image 30a to the web 16 is present. When an image is formed by this printer, there is a problem that an image defect occurs.

  FIG. 9 is a schematic view showing a web stop state of the fixing unit in which the B section is enlarged. As shown in the figure, the fixing unit includes a preheater 32 that preheats by contacting the web 16, a heating roll 33 that includes a heater, a backup roll 34 that pressurizes the heating roll 33, and the like.

  The fixing unit continues to supply heat to the web 16 during continuous printing. When the printing is stopped, the supply of heat is stopped. However, immediately after the printing is stopped, the response is poor and an overshoot occurs. Therefore, the web 16 on the preheater 32 is thermally contracted in the direction of the arrow in the figure, or the web is uneven due to thermal damage. Therefore, when printing is restarted, an image defect is likely to occur when the web portion stopped on the preheater 32 of the first printer P1 passes through the image forming unit of the second printer P2.

  In order to solve such a problem, a method of pressing a web against the surface of a photosensitive member by providing a transfer assist blade has been known. By providing the transfer assist blade, it becomes possible to reduce the unevenness of the web surface and the gap between the photosensitive drums, and good transfer can be obtained.

  However, in the case of duplex printing, when a toner image is printed on the second surface of the web, since the toner image is already formed on the first surface, it contacts the transfer assist blade of the web conveyed to the transfer unit housing. The first surface on which the toner image is formed comes to the surface. For this reason, the surface of the toner image fixed by the transfer assist blade is rubbed, and a part of the toner adheres to the transfer assist blade and becomes dirty, resulting in deterioration of the image formed on the first surface.

  In general, when printing to form an image on the second surface of the web, the transfer history is improved in order to improve adhesion because the web is deformed due to the heat history during the fixing process during the printing of the first surface. It is necessary to increase the pressing pressure of the blade. For this reason, the problem of further promoting blade contamination arises.

  On the other hand, as other transfer means, a transfer roll and a transfer belt system are generally known, and are employed in medium- and low-speed cut sheet printers. Compared with the non-contact corotron transfer system, the transfer roll is brought into contact with an appropriate pressing force, so that it is possible to reduce the gap between the web surface as described above and the photosensitive drum.

In the transfer roll, in order to transfer the toner image developed on the photoreceptor onto the web surface by electrostatic force, an electric charge is supplied to the transfer roll to perform transfer. As means for supplying electric charge to the transfer roll, there are known a method of applying an electric current to the core of the transfer roll and a method of supplying a charge necessary for transfer from the surface of the transfer roll by providing a dielectric layer on the surface of the transfer roll. It has been.
Japanese Patent Publication No.57-10427 Japanese Patent Publication No.62-3423

  The former method of applying an electric current to the core of the transfer roll is mainly used in cut paper printers in the middle and low speed range. Since the surface charge required for transfer must be increased as the printing speed increases, it is necessary to increase the nip width between the transfer roll and the web. In order to increase the nip width, it is sufficient to increase the roll diameter, increase the thickness of the elastic body, decrease the hardness of the elastic body, etc., but increase the device space by increasing the roll diameter and increasing the elastic body thickness, the hardness of the elastic body The problem of roll life reduction due to expansion of roll deformation due to reduction occurs.

  The latter method of supplying the charge required for transfer from the surface of the transfer roll does not increase the nip width with respect to the printing speed, and the surface dielectric layer also serves as a protective layer. Can be prevented. However, a charging device for supplying electric charges and a static eliminator for removing electric charges on the surface of the transfer roll are required, resulting in high costs.

  In addition, when the transfer roll is applied to a continuous paper printer, the following points need to be considered. In general, the transfer roll is used by following the web. In the case of cut paper, the web is cut for each sheet, so the printing is completed until the fixing process, and the toner is not fixed on the web. Since stopping in the apparatus in the state is not a normal operation, the transfer roll can be brought into contact with the photosensitive member or the intermediate transfer belt in advance.

  However, in the case of continuous paper, printing may stop in the middle of a job, and an unfixed image exists except for a non-printing area between pages. Usually, in order to ensure the next run distance for the next printing, the web returns as much as necessary, and at the time of start-up, the web is started up to a specified speed using the run distance. Therefore, in the case of continuous paper, the transfer roll must be separated from the web when printing is stopped from the viewpoint of image deterioration, and a web contact / separation operation is required.

  The web separation / contact operation must be performed between the non-printing area at the trailing end of the stop portion and the non-printing area at the leading end of the first page. At this time, in the case of applying the current to the core of the transfer roll as described above, the current flows from the inside at any time. Therefore, even if the rotation speed of the transfer roll itself is delayed with respect to the web conveyance speed, the transfer is performed. Not affected by sex. However, in the method of supplying the charge necessary for transfer from the transfer roll surface advantageous for high speed, the transfer roll does not rotate between the charge supply position of the transfer roll and the transfer point at the start of printing. During that time, transcription is not possible. Therefore, when the transfer roll is driven, there is a problem that transfer cannot be performed at the start-up. Further, there is a problem in the followability of the transfer roll in the high speed region.

  In general, when a transfer roll is used, a cleaning member for removing toner and paper dust adhering to the surface of the transfer roll is necessary. As a cleaning method, there are a method combining brush and air suction, a method combining blade and auger, and the like. The method of combining brush and air suction is used in high-speed machines, but it is reliable, but it is expensive and increases the mounting space.

  On the other hand, the low speed machine employs a blade system or a brush system, and is provided with a recovery mechanism that recovers the dammed toner with an auger or the like. In the case of the blade method, it is inexpensive and space-saving is possible. However, when used in a long and high speed machine, keeping the blade pressed against the transfer roll has a problem in the life of the transfer roll and the blade.

  The object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to produce a high quality image that does not cause image defects even on rough paper, a thermally deformed recording medium or various recording media having different widths. An object of the present invention is to provide an image forming apparatus capable of forming an image.

In order to achieve the above object, the first means of the present invention includes an image carrier such as a photoreceptor carrying a toner image, and
Image carrier rotation driving means for rotating the image carrier;
Transfer means for transferring the toner image on the image carrier onto a recording medium;
Transport means for transporting the recording medium between the image carrier and transfer means;
The transfer means includes
A transfer member having a dielectric layer on the surface, a transfer member charging unit for charging the surface of the transfer member from the outside, a transfer member discharging unit for discharging the surface of the transfer member, and a transfer for cleaning the surface of the transfer member In the image forming apparatus provided with the member cleaning means,
Contact / separation means for contacting or separating the transfer member from the image carrier via the recording medium;
A transfer member rotation driving means for rotating the transfer member in the same direction as the conveyance direction of the recording medium;
The transfer member rotation driving means is interlocked with the image carrier rotation driving means.

  According to a second means of the present invention, in the first means, the transfer member is rotated by the transfer member rotation driving means before the transfer member is moved toward the image carrier by the contact / separation means, The transfer member is cleaned by the transfer member cleaning means.

  According to a third means of the present invention, in the first or second means, the transfer member rotation driving means stops the rotation of the transfer member after the transfer member is separated from the image carrier side by the contact / separation means. In the meantime, the transfer member is cleaned by the transfer member cleaning means.

  According to a fourth means of the present invention, in the first to third means, the transfer member cleaning means is a position that does not interfere with the contact / separation operation of the transfer member, and the transfer member is separated from the image carrier. The retracted position is fixed at a position where it abuts on the transfer member.

  According to a fifth means of the present invention, in the first to fourth means, the transfer member is neutralized by the transfer member neutralizing means when the transfer member is cleaned.

  According to a sixth means of the present invention, in the first to fifth means, the transfer member neutralizing means is located at a position not interfering with the contact / separation operation of the transfer member, and the image carrier via the recording medium. The transfer member is fixed at a predetermined interval with respect to the position of the transfer member when abutting on the transfer member.

  According to a seventh means of the present invention, in the first to sixth means, the transfer member is driven by the transfer member rotation driving means until the transfer member contacts the image carrier via the recording medium. And the charging of the transfer member is started by the transfer member charging means.

  According to an eighth means of the present invention, in the first to seventh means, the transfer member charging means is located at a position that does not interfere with the contact / separation operation of the transfer member and the image carrier via the recording medium. The transfer member is fixed at a predetermined interval with respect to the position of the transfer member when abutting on the transfer member.

According to a ninth means of the present invention, in the first to eighth means, the transfer member, the transfer member charging means, the transfer member discharging means, and the transfer member cleaning means are accommodated, and an opening is formed on the side facing the recording medium. A transfer device housing having
The transfer member and the transfer device housing are reciprocated by the contact / separation means, and the transfer member charging means, the transfer member discharging means, and the transfer member cleaning means are in a fixed state.

  According to a tenth means of the present invention, in the first means, a portion of the transfer member charging means corresponding to a non-sheet-passing region where the recording medium does not pass is provided with a shielding member between the transfer member and the transfer member charging means. Is covered with the shielding member.

  According to an eleventh means of the present invention, in the tenth means, there is provided a shielding member moving means for moving the shielding member in accordance with the width of the recording medium, and the shielding member moving means in the middle of continuous image formation. Thus, the shielding release and shielding operation of the shielding member are periodically performed.

The twelfth means of the present invention comprises an image carrier for carrying a toner image,
Transfer means for transferring the toner image on the image carrier onto a continuous long recording medium;
Transport means for transporting the recording medium between the image carrier and transfer means;
A first image forming apparatus and a second image forming apparatus provided with fixing means for heating and fixing the toner image transferred onto the recording medium;
In the tandem type image forming apparatus for forming the first image and the second image on the continuous long recording medium by the first image forming apparatus and the second image forming apparatus,
The first image forming apparatus and the second image forming apparatus are image forming apparatuses of the first to eleventh means.

  The present invention has the above-described configuration, and can form a high-quality image that does not cause image defects even on rough paper, a thermally deformed recording medium, or various recording media having different widths. A forming apparatus can be provided.

  Hereinafter, an overall apparatus configuration of an image forming apparatus according to an embodiment of the present invention will be described, and then a configuration and operation of a transfer unit, which is a main part of the invention, and a configuration and operation of a transfer roll will be described in this order.

(1) Overall Apparatus Configuration FIG. 10 is an overall configuration diagram of an image forming apparatus according to an embodiment of the present invention. As shown in the figure, a charger 2, an exposure device 3, a developing machine 4 and a transfer unit 6 are arranged along the rotation direction of the photosensitive member 1 as shown in the figure. After the charger 2 uniformly charges the surface of the photosensitive member 1, the exposure device 3 irradiates the surface of the photosensitive member 1 with laser light according to image data. As a result, an electrostatic latent image is formed on the surface of the photoreceptor 1 and is developed by the developing device 4 to form a toner image on the surface of the photoreceptor 1.

  On the other hand, the web 16 is conveyed to the transfer unit 6 by the web conveyance device 17, and the toner image is transferred onto the web 16 by the transfer unit 6. When the toner image on the web 16 passes through the preheater 32, it is heated to near the glass transition temperature of the toner resin, and then the toner image is transferred to the web 16 by a fixing device 35 including a heating roll 33 and a backup roll 34 incorporating the heater. It is melted and fixed. In the case of duplex printing, two image forming apparatuses are used as shown in FIG. The present invention is characterized by the structure of the transfer section in this image forming apparatus.

(2) Configuration of Transfer Unit FIGS. 1 and 2 are diagrams showing a printing process and a configuration of the transfer unit in the image forming apparatus of the present invention. FIG. 1 is a schematic diagram of the image forming apparatus showing a state during printing. FIG. 2 is a schematic diagram of the image forming apparatus showing a standby state during non-printing. 3 and 4 are diagrams for explaining the drive system of the transfer roll.

  The transfer unit 6 includes an upper guide separator 8 a and a lower separator 8 b that guide the web 16, and is opened toward the photoreceptor 1. The transfer unit 7 is housed therein, the transfer roll 9 is stored therein, and the surface of the transfer roll 9. A corona charger 10 for supplying electric charge to the surface, a static eliminator 11 for neutralizing the surface of the transfer roll 9 after transfer, a cleaner 12 for cleaning toner, paper dust, etc. on the surface of the transfer roll 9, a retract motor 23, and a cam arm 24. Etc.

  The transfer roll 9, the corona charger 10, the static eliminator 11, and the cleaning machine 12 are stored in a transfer device housing 7. The transfer housing 7 and the output shaft of the retract motor 23 are connected by a cam arm 24.

  The transfer roll 9 is provided with a lower layer made of a non-conductive elastic layer on a cored bar, an intermediate layer made of a conductive elastic layer provided thereon, and a fluorine-based non-conductive material thereon. It has a three-layer structure in which a surface layer made of a tube is provided. Note that a two-layer structure in which a lower layer made of a conductive elastic layer is provided on a cored bar and a surface layer made of a fluorine-based nonconductive tube is provided thereon may be used. As the fluorine-based non-conductive tube, for example, a PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) tube having a thickness of about 30 to 100 μm is used.

  As shown in FIG. 3, both ends of the transfer roll 9 are rotatably supported by bearing-embedded arms 13 a and 13 b, and the base end of the arm 13 is supported by an arm support shaft 20. Although not shown, the transfer device housing 7 is also supported by the arm support shaft 20 via the arm. Therefore, as shown in FIGS. 1 and 2, the transfer device housing 7 and the transfer roll with the arm support shaft 20 as the rotation center. 9 swings and the contact / separation operation with respect to the photoreceptor 1 is performed.

  As shown in FIG. 3, both end portions of the photoreceptor 1 and both end portions of the arm support shaft 20 are rotatably supported by a support plate 19. A first pulley 21 a is provided at one end of the transfer roll 9, a second pulley 21 b and a third pulley 21 c are provided at one end of the arm support shaft 20, and a fourth pulley is provided at one end of the rotating shaft of the photoreceptor 1. A fifth pulley 21e and a sixth pulley 21f are fixed to the output shaft of the photosensitive member driving motor 22 and the pulley 21d. A first timing belt 14a is provided between the first pulley 21a and the second pulley 21b, a second timing belt 14b is provided between the third pulley 21c and the fifth pulley 21e, and a fourth pulley 21d and a sixth pulley. The third timing belt 14c is stretched between 21f.

Accordingly, the rotational driving force of the photosensitive member driving motor 22 is transmitted to the photosensitive member 1 via the sixth pulley 21f, the third timing belt 14c, and the fourth pulley 21d, and the fifth pulley 21e, the second timing belt 14b, The transfer roller 9 is transmitted to the transfer roller 9 via the three pulleys 21c, the arm support shaft 20, the second pulley 21b, the first timing belt 14a, and the first pulley 21a. In this embodiment, the structure is linked to the photosensitive member driving motor 22, but an individual driving source may be provided.

  Reference numerals 17a and 17b shown in FIG. 1 and FIG. 2 denote web transport devices made of tractors, which transport the web 16 by being fitted into the feed holes of the web 16. The web conveyance devices 17a and 17b are arranged on the upstream side and the downstream side of the transfer unit 6 and are rotated synchronously by one drive system.

  As shown in FIGS. 1 and 2, the transfer roll 9 supported by the arm 13 swings around the arm support shaft 20. The tip of the spring 15 is in contact with one end of the arm 13 so that an appropriate pressing force can be applied to the photosensitive member 1 to form a nip portion having a predetermined length, and the base end of the spring 15 is a transfer device. It is in contact with the wall surface of the housing 7. Further, a stopper 18 is mounted on the transfer device housing 7 at a position close to the arm 13 in order to perform the separation / contact operation of the transfer roll 9. As shown in FIG. 1, the stopper 18 is in a positional relationship to be separated from the arm 13 during printing.

  A retract motor 23 is installed on the side of the transfer unit housing 7 opposite to the photosensitive member 1, and the output shaft of the retract motor 23 and the transfer unit housing 7 are connected by a cam arm 24.

Next, the operation of the transfer unit 6 will be described.
(3) Operation of Transfer Unit As shown in FIG. 2, when the printer is on standby, the transfer device housing 7 is in a position retracted from the photoreceptor 1, and the transfer roll 9 supported thereby is not in contact with the photoreceptor 1. It is in the state of. Since the web 16 is always in contact with the upper guide separator 8a and the lower guide separator 8b attached to the opening of the transfer unit housing 7, the web 16 is also not in contact with the photoreceptor 1 by the retreat of the transfer unit housing 7. It is in the state of. Due to the elastic force of the spring 15, the tip of the arm 13 is in contact with the stopper 23.

  When the print start signal is transmitted to the image forming apparatus, the photosensitive member driving motor 22 rotates, and the photosensitive member 1 rotates accordingly, and the charger 2, the developing device 4, and the cleaning device 5 start operating. The printing process is ready. Thereafter, exposure starts from the exposure device 3, a latent image is formed on the photoreceptor 1, passes through the developing device 4, a toner image is formed on the photoreceptor 1, and is sent to the transfer unit 6.

  Since the transfer roll 9 is connected to the photosensitive member drive motor 22 via each timing belt 14 and the pulley 21, the transfer roll 9 rotates in accordance with the operation of the photosensitive member 1. Based on the web 16 transport operation signal, transport of the web 16 by the tractors 17a and 17b is started, and the transport speed of the web 16 rises to a predetermined speed before reaching the transfer point to complete preparation for the transfer operation.

  The retract motor 23 rotates with a slight delay from the start of the conveyance operation of the web 16, whereby the transfer housing 7 starts to swing around the arm support shaft 20 by the cam arm 24. This operation is completed before and after the conveyance of the web 16 reaches the transfer point, and the web 16 comes into contact with the photoreceptor 1 to form a nip portion having an appropriate nip width.

  When the transfer roll 9 is on standby, the arm 13 and the stopper 18 are in contact with each other by the elastic force of the spring 15 (see FIG. 2). During the swinging motion of the transfer housing 7, the transfer roll 9 comes into contact with the photoreceptor 1, the arm 13 is separated from the stopper 18 by further movement of the transfer housing 7, and the transfer roll 9 is appropriately pressed by the elastic force of the spring 15. Is applied to the photosensitive member 1, and the nip between the photosensitive member 1, the web 16, and the transfer roll 9 is completed (see FIG. 1). The time to complete this nip is in the non-printing area between pages. In the separation / contact operation of the transfer roll 9, the photosensitive member 1 and the transfer roll 9 come into contact with each other while rotating in the same direction.

  Note that the charger 10, the static eliminator 11, and the cleaner 12 are fixed and supported in the transfer housing 7 regardless of the swinging operation of the transfer housing 7.

  The ON operation of the charger 10 for supplying the charge to the transfer roll 9 is already performed at the timing when the charge is already on the surface of the transfer roll 9 when the transfer is started. It should be noted that when printing is stopped, the procedure is the reverse of the startup operation, and the next printing operation is prepared.

Next, the cleaning operation of the transfer roll 9 will be described.
(4) Operation when cleaning the transfer roll
In FIG. 1, the distance L1 between the transfer roll 9 and the charger 10 in the printing state and the distance L2 between the transfer roll 9 and the charge eliminator 11 are maintained so as to have an optimum positional relationship for transfer performance.

  Since the transfer roll 9 needs to perform the contact / separation operation with respect to the photoreceptor 1 in a short time, it is necessary to suppress the weight as much as possible. The movement of the unit including the charger 10, the static eliminator 11, the cleaner 12, and the like attached around the transfer roll 9 is heavy, so that the image quality deteriorates due to the influence of the vibration of the transfer roll unit at the nip at start-up Invite.

  Therefore, the positions of the charger 10 and the static eliminator 11 are arranged so as not to interfere with the separation / contact operation of the transfer roll 9, and are set to distances L1 and L2 that are optimal for transfer in a printing state. Thereby, the charger 10, the static eliminator 11, and the cleaner 12 can be fixed, and the weight of the movable part can be suppressed as much as possible.

  The cleaning machine 12 is separated from the transfer roll 9 during printing (see FIG. 1), and is in a position where it comes into contact with the transfer roll 9 during standby when the transfer unit housing 7 and the transfer roll 9 are retracted from the photoreceptor 1 (FIG. 2). reference). That is, the cleaning operation of the transfer roll 9 is performed in the retracted state after the start and completion of the printing operation without performing the cleaning operation during printing. A cleaning machine 12 composed of a roll brush performs a cleaning operation of the transfer roll 9 while rotating with the transfer roll 9.

Next, the operation of the transfer section during the cleaning will be described using the operation sequence of FIG.
At the time of standby before printing, the web 16 and the photoreceptor 1 are separated as shown in FIG. When a printing operation signal is sent from the control, the rotating operation of the photosensitive member 1 is started. At the same time, the photosensitive member charger 2, the developing device 4, and the cleaning device 5 start to operate and become ready for printing.

  Since the transfer roll 9 is connected to the photoreceptor 1, rotation starts at the same timing as the photoreceptor 1. At this time, the transfer roll 9 is in the standby position of FIG. 2 and is in contact with the cleaning machine 12, and cleaning is started simultaneously with the rotation of the transfer roll 9 (t1), and the toner and paper dust adhering to the surface are cleaned. Removed by machine 12.

  At this time, the transfer roll charger 10 is not turned ON, but only the transfer roll neutralizer 11 is turned ON simultaneously with the start of the rotation operation of the transfer roll 9. Since the surface layer of the transfer roll 9 is composed of a high-resistance synthetic resin layer (tube), basically, the charges charged on the surface hardly escape. During printing, a charge necessary for transfer is supplied to the transfer roll 9 by the charger 10, and charge is supplied to the photosensitive member 1 at the nip portion of the transfer roll 9, so that the surface potential of the transfer roll 9 after the nip is lowered. Thereafter, the charge is further eliminated by the static eliminator 11 to prepare for the next printing cycle.

  When printing is stopped, the web 16 and the transfer roll 9 are retracted from the photoreceptor 1. However, the charge on the surface of the transfer roll 9 is not supplied to the photoreceptor 1 when it is separated from the photoreceptor 1. Although it does, it has not been completely removed. In that case, the toner on the transfer roll 9 is electrostatically adsorbed on the roll surface and is difficult to remove. For this reason, when the transfer roll 9 is cleaned, the charge eliminator 11 is turned on to remove charges and improve the cleanability.

  When the transfer roll 9 swings toward the photoreceptor 1, the transfer roll 9 moves away from the cleaning machine 12, and thus cleaning is completed at that time (t 2). Therefore, the cleaning time TA of the transfer roll 9 before printing is from the time when the transfer roll 9 starts to rotate until the transfer roll 9 leaves the cleaning machine 12 (t1 to t2) as shown in FIG.

  A web feed signal is sent shortly before the cleaning before printing is completed, and the web 16 starts to be transported. The transfer housing 7 and the transfer roll 9 swing in accordance with the transport speed of the web 16 reaching the specified speed. The transfer operation is completed from the transfer point.

  When printing is stopped, the transfer housing 7 and the transfer roll 9 are retracted from the photoreceptor 1 at almost the same timing as the stop of the web conveyance, and the transfer roll charger 10 is turned off. The photoreceptor 1 and the transfer roll 9 continue to rotate for a fixed time even when the conveyance of the web 16 is stopped, and the transfer roll static eliminator 11 is also turned on for a fixed time.

  The cleaning time TB after printing starts from when the transfer roll 9 is retracted and contacts the cleaning machine 12 until the transfer roll 9 starts cleaning (t3) and the transfer roll 9 stops rotating (t4). . After a certain period of time has passed, the rotation operation of the photosensitive member 1 and the transfer roll 9 is stopped, and the static eliminator 11 is turned off to complete a series of operations to prepare for the next printing.

  According to this embodiment, there is no need to always contact the transfer roll cleaner 12 with the transfer roll 9, so that the life of the transfer roll 9 and the transfer roll cleaner 12 can be extended.

Next, the configuration and operation of the corotron mask 25 will be described.
(4) Operation of Corotron Mask 25 FIGS. 6 and 7 show the configuration of the transfer roll 9, the transfer roll charger 10, and the corotron mask 25. FIG. FIG. 5 is a top view of the corotron mask portion, and FIG. 6 is a front view of the corotron mask portion.

  The corotron mask 25 is made of a thin synthetic resin sheet, and is provided to prevent contamination of the wire 26 of the transfer roll charger 10 with toner. The web 16 has a wide variety of widths. Depending on the width of the web 16, as shown in FIG.

  Since the web 16 exists between the transfer roll 9 and the photoreceptor 1 in the sheet passing area, the toner from the photoreceptor 1 does not adhere to the transfer roll 9, but in the non-sheet passing area, the toner on the photoreceptor 1 is not nipped during nip. It adheres to the transfer roll 9 and the transfer roll 9 becomes dirty. Therefore, when there is no corotron mask 25, the wire 26 of the transfer roll charger 10 is soiled in the non-sheet passing portion region. If the wire 26 becomes dirty, stable corona supply cannot be performed, so that the surface potential of the transfer roll 9 becomes non-uniform in the width direction, causing problems such as transfer failure.

  Further, depending on the presence or absence of the corotron mask 25, there is a difference in dirt in the non-sheet passing portion region of the transfer roll 9. In the absence of the corotron mask 25, the surface potential of the transfer roll 9 is irradiated with corona from the charger 10, and thus has a surface potential of +1.0 to 2.0 kV as in the case of paper passing. Since the surface potential of the photosensitive member 1 and the toner polarity on the photosensitive member 1 are opposite in polarity, the toner adhering to the photosensitive member 1 is electrostatically pulled toward the transfer roll 9 side. Conversely, the toner adhering to the transfer roll 9 is charged to the + side by the charger 10 and is therefore pulled to the photoreceptor 1 side. Accordingly, the toner contamination on the transfer roll 9 is transferred as described above, so that it becomes saturated at some point.

  When the corotron mask 25 is present, the corona irradiation from the charger 10 is shielded by the corotron mask 25, so that the surface of the transfer roll 9 is not charged. Therefore, the toner contamination due to the reverse polarity as described above is not saturated, and the amount of toner on the surface of the transfer roll 9 is increased as compared with the case where the corotron mask 25 is provided, which imposes a burden on the cleaner 12 of the transfer roll 9. This causes problems such as short life.

  Next, the configuration of the corotron mask 25 will be described. The charger 10 that charges the surface of the transfer roll 9 is arranged at a fixed interval with respect to the transfer roll 9. The charger 10 includes a corona wire 26 and a shield 37, and irradiates the corona with a high voltage power source (not shown).

  The corotron mask 25 is wound around a reel 27, the tip end portion is sandwiched between holding members 28, and the upper end portion of the holding member 28 is connected to a part of an endless pulling wire 29. As shown in FIG. 6, a mask moving motor 31 is disposed in the vicinity of the reel 27, and the reel 27 and the mask moving motor 31 are connected by a timing belt 36.

  The mask moving motor 31 is rotationally driven based on the paper width information, and the corotron mask 25 slides in the horizontal direction according to the paper width and moves to a specified position to shield the corona wire 26 and the shield 37.

  Normally, the corotron mask 25 is not moved unless the paper width is changed. However, in this embodiment, the corotron mask 25 has an arbitrary period in a state where the transfer roll 9 during continuous printing is nipped with the photosensitive member 1. 25 is wound to the reel 27 side to be fully opened, and a charge is supplied from the charger 10 to the portion corresponding to the non-sheet passing area of the transfer roll 9 for a certain period of time. By providing this charge supply time during continuous printing, the toner contamination saturation state as described above can be made periodically, and both the contamination of the charger 10 and the prevention of contamination of the transfer roll 9 can be satisfied. .

  In the above embodiment, a roll-shaped transfer member is used, but the present invention is not limited to this, and a belt-shaped transfer member can also be used.

  In the above embodiment, the transfer source is divided into the photosensitive member drive system and the transfer roll drive system, and the transfer roll is rotated synchronously with the photosensitive member. However, the photosensitive member drive system is provided from the drive source, and the transfer roller is transferred from the photoreceptor drive system. A drive system can also be provided to rotate the transfer roll synchronously with the photoreceptor.

The effects of the present invention are summarized as follows.
(1) Even when rough paper having large irregularities on the surface is used, good transfer without image defects becomes possible.

(2) When double-sided printing is performed with a tandem type image forming apparatus, even if the web is thermally deformed with the first image forming apparatus, image transfer omission is prevented during transfer in the second image forming apparatus. Image defects can be reduced.

(3) Since the driving means for rotating the transfer roll is provided, it is possible to ensure transferability at the start of printing in the transfer system that supplies charges necessary for transfer from the transfer roll surface. For this reason, it is possible to suppress transfer failure due to deterioration in followability of the transfer roll.

(4) Since the transfer roll is cleaned before the start of printing and during non-printing after the start of printing, the life of the cleaning member and the transfer roll can be extended.

(5) In an external charging type transfer system that supplies charges necessary for transfer from the surface of the transfer roll, a shielding member that shields the wire of the charger that charges the surface of the transfer roll according to the paper width is continuously printed. Since control is provided to perform an operation of fully opening (no shielding with respect to the photoconductor) for a certain period which is an arbitrary cycle, the toner adhering to the non-sheet passing area can be moved to the photoconductor side periodically, and the transfer roll The amount of waste toner adhering to the toner can be reduced.

1 is a schematic diagram of an image forming apparatus illustrating a state during printing according to an embodiment of the present invention. It is a schematic diagram of an image forming apparatus showing a standby state during non-printing according to an embodiment of the present invention. It is a diagram for explaining a drive system of a transfer roll of the image forming apparatus. It is a diagram for explaining a drive system of a transfer roll of the image forming apparatus. 6 is a timing chart illustrating the operation of a transfer unit in the image forming apparatus according to the exemplary embodiment of the present invention. It is a top view which shows the structure of the corotron mask part which concerns on the Example of this invention. It is a front view which shows the structure of the corotron mask part which concerns on the Example of this invention. It is explanatory drawing of tandem printing. It is a perspective view which shows the state of the web stopped on the fixing device at the time of printing stop. 1 is a schematic configuration diagram illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1: Photoconductor, 6: Transfer part, 7: Transfer device housing, 8a, 8b: Guide separator, 9: Transfer roll, 10: Corona charger, 11: Static eliminator, 12: Cleaning machine, 13: Arm, 14: Timing belt, 15: spring, 16: web, 17: web conveying device, 18: stopper, 20: arm support shaft, 21: pulley, 22: photosensitive member drive motor, 23: retract motor, 24: cam arm, 25: roller Tron mask, 26: corotron wire, 27: reel, 28: holding member, 29: pulling wire, 30: image, 31: motor for moving mask, 36: timing belt, 37: shield, P1: first printer, P2: Second printer, T: Turn bar.

Claims (12)

An image carrier for carrying a toner image;
Image carrier rotation driving means for rotating the image carrier;
Transfer means for transferring the toner image on the image carrier onto a recording medium;
Transport means for transporting the recording medium between the image carrier and transfer means;
The transfer means includes
A transfer member having a dielectric layer on the surface, a transfer member charging unit for charging the surface of the transfer member from the outside, a transfer member discharging unit for discharging the surface of the transfer member, and a transfer for cleaning the surface of the transfer member In the image forming apparatus provided with the member cleaning means,
Contact / separation means for contacting or separating the transfer member from the image carrier via the recording medium;
A transfer member rotation driving means for rotating the transfer member in the same direction as the conveyance direction of the recording medium;
The image forming apparatus, wherein the transfer member rotation driving means is interlocked with the image carrier rotation driving means.   2. The image forming apparatus according to claim 1, wherein the transfer member is rotated by the transfer member rotation driving unit before the transfer member is moved toward the image carrier by the contact / separation unit, and the transfer member cleaning unit is rotated. A transfer member is cleaned by the image forming apparatus.   3. The image forming apparatus according to claim 1, wherein after the transfer member is separated from the image carrier side by the contact / separation means, the rotation of the transfer member is stopped by the transfer member rotation driving means. The transfer member is cleaned by the transfer member cleaning means.   4. The image forming apparatus according to claim 1, wherein the transfer member cleaning unit is a position that does not interfere with the contact and separation of the transfer member, and the transfer member is separated from the image carrier. An image forming apparatus, wherein the image forming apparatus is fixed to a position in contact with the transfer member at the retracted position.   5. The image forming apparatus according to claim 1, wherein the transfer member is neutralized by the transfer member neutralizing unit when the transfer member is cleaned. 6.   6. The image forming apparatus according to claim 1, wherein the transfer member neutralizing unit is located at a position that does not interfere with the contact / separation operation of the transfer member and through the recording medium. An image forming apparatus, wherein the image forming apparatus is fixed to a position at a predetermined interval with respect to the position of the transfer member when abutting on the image forming apparatus.   The image forming apparatus according to claim 1, wherein the transfer member is driven by the transfer member rotation driving unit until the transfer member contacts the image carrier via the recording medium. And the transfer member charging means starts charging the transfer member.   8. The image forming apparatus according to claim 1, wherein the transfer member charging unit is located at a position that does not interfere with the contact / separation operation of the transfer member and through the recording medium. An image forming apparatus, wherein the image forming apparatus is fixed to a position at a predetermined interval with respect to the position of the transfer member when abutting on the image forming apparatus. 9. The image forming apparatus according to claim 1, wherein the transfer member, the transfer member charging unit, the transfer member discharging unit, and the transfer member cleaning unit are accommodated, and an opening is formed on a side facing the recording medium. A transfer device housing having
The image forming apparatus, wherein the transfer member and the transfer device housing are reciprocated by the contact / separation unit, and the transfer member charging unit, the transfer member discharging unit, and the transfer member cleaning unit are in a fixed state.   2. The image forming apparatus according to claim 1, wherein a shielding member is provided between the transfer member and the transfer member charging unit, and a portion of the transfer member charging unit corresponding to a non-sheet passing region through which the recording medium does not pass is provided. An image forming apparatus characterized by being covered with.   The image forming apparatus according to claim 10, further comprising: a shielding member moving unit that moves the shielding member in accordance with a width of the recording medium, and the shielding member moving unit performs the shielding member during the continuous image formation. The image forming apparatus is characterized by periodically performing shielding release and shielding operation. An image carrier for carrying a toner image;
Transfer means for transferring the toner image on the image carrier onto a continuous long recording medium;
Transport means for transporting the recording medium between the image carrier and transfer means;
A first image forming apparatus and a second image forming apparatus provided with fixing means for heating and fixing the toner image transferred onto the recording medium;
In the tandem type image forming apparatus for forming the first image and the second image on the continuous long recording medium by the first image forming apparatus and the second image forming apparatus,
The tandem type image forming apparatus according to any one of claims 1 to 11, wherein the first image forming apparatus and the second image forming apparatus are image forming apparatuses according to any one of claims 1 to 11.

Images