JP2013160923A - Image forming apparatus and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration of members involved in image formation and to suppress deterioration in image quality due to decrease of transfer rate of toner even when a sheet having a low surface smoothness is used.SOLUTION: An image forming apparatus 100 comprises a sheet conveyance part 206, an image forming part 110 and a control part 200. The image forming part 110 includes a transfer part 207 which performs transfer processing in which a toner image is transferred to a sheet, and a fixing unit 70 which performs fixing processing in which the sheet is heated and pressed. Under a prescribed condition, the control part 200 performs smoothing processing in which the fixing processing is performed on a sheet without performing the transfer processing. When the control part 200 performs smoothing processing, it stops or slows down at least one operation among the operations of the sheet conveyance part 206 and the image forming part 110 in the case of forming an image on a sheet, with the exception of the fixing processing.

Description

  The present invention relates to an image forming apparatus and an image forming method in which a toner image carried on an image carrier is transferred to paper and fixed by heating and pressurizing the paper.

  In an electrophotographic image forming apparatus, a toner image is carried on an image carrier, the toner image is transferred to a sheet by a transfer unit, and the toner image is fixed to the sheet by being heated and pressed by a fixing unit. As a result, an image is formed on the sheet.

  Among papers on which images are formed by such an image forming apparatus, papers with rough eyes, embossed papers that are intentionally embossed on the surface, papers that are used in a form that is folded in two or in three. For example, there are sheets with low surface smoothness.

  When an electrophotographic image forming process is performed on a sheet having a large surface irregularity, there is a problem that the toner transfer rate is lowered due to the surface irregularity and the image quality is deteriorated.

  Therefore, the surface smoothness of the paper is measured by the paper smoothness measuring member, and when the smoothness is lower than a predetermined level, the fixing unit is configured to sandwich the paper between the heating roller and the pressure roller without performing an image forming operation on the paper. There is known an image forming apparatus that performs smoothing by passing the image, and then guides it to a conveyance path for double-sided printing to form an image (see, for example, Patent Document 1).

JP-A-4-315162

  However, although Patent Document 1 describes that no image forming operation is performed on a sheet, there is no description about an operation related to image formation other than the image forming operation on a sheet. In addition, as an image forming operation to be performed on the paper before passing through the fixing unit, it is described that the visible image on the surface of the photosensitive drum is transferred to the surface of the paper, but the operation other than the transfer is described. There is no.

  For this reason, in the conventional image forming apparatus described in Patent Document 1, the rotation of the photosensitive drum and the registration roller pair are performed when the sheet is passed between the heating roller and the pressure roller without performing the image forming operation. It is considered that operations related to image formation such as transport control by the same are performed in the same way as when performing image formation.

  For this reason, in the conventional image forming apparatus, when the operation of passing through the fixing unit is executed to smooth the paper, the members involved in the image formation are deteriorated due to wear or the like even though the image formation is not performed. To do.

  An object of the present invention is to provide an image forming apparatus and an image forming method capable of suppressing deterioration in image quality due to a decrease in toner transfer rate even on a sheet having low surface smoothness while suppressing deterioration of members involved in image formation. It is to provide.

  An image forming apparatus according to the present invention includes a paper transport unit, an image forming unit, and a control unit. The paper transport unit transports paper. The image forming unit is disposed on the downstream side of the image carrier, a transfer unit that performs a transfer process for transferring the toner image carried on the image carrier to the paper conveyed by the paper conveyance unit, and the transfer unit in the paper conveyance direction. A fixing unit that performs a fixing process of heating and pressing the sheet. The control unit controls operations of the paper transport unit and the image forming unit. The control unit executes a smoothing process that performs a fixing process on the paper without performing a transfer process under a predetermined condition. When the control unit executes the smoothing process at least one of the operations of the sheet transport unit and the image forming unit except for the fixing process when the image is formed on the sheet with the transfer process. Stop or slow down.

  In this configuration, the smoothing process is performed under a predetermined condition, so that the paper is heated and pressurized without transferring the toner image. Therefore, even if the paper has low surface smoothness, the surface is smooth. It becomes. For this reason, after the smoothing process is performed, the sheet is conveyed again to the transfer unit and the transfer process is performed, whereby the toner transfer rate is improved and the deterioration of the image quality is suppressed. In addition, when the smoothing process is performed, the operation of the members included in the sheet conveying unit and the image forming unit when the image is formed on the sheet with the transfer process, that is, the operation of the members involved in the image formation. Since at least one operation other than the fixing process is stopped or decelerated, deterioration due to wear or the like of members involved in image formation can be suppressed.

  In the above-described configuration, the paper transport unit has a transport path for transporting the paper subjected to the fixing process in the fixing unit to the transfer unit again, and the control unit performs the smoothing process a plurality of times under a predetermined condition. It can be configured such that the sheet is conveyed again to the transfer unit and the transfer process is performed. In this configuration, since the smoothing process is repeated a plurality of times, the smoothness of the surface of the paper can be further increased.

  Further, the fixing unit can be configured to change the setting of the pressing force, and the control unit can be configured to improve the pressing force in the fixing unit when executing the smoothing process. In this configuration, the pressure applied to the sheet at the fixing unit during the smoothing process is improved, so that the smoothness of the surface of the sheet can be further increased.

  Further, the control unit can be configured not to execute the image quality adjustment process even when the execution time of the image quality adjustment process comes, during the smoothing process. In this configuration, since the smoothing process can be completed in a short time, the image formation can be completed early.

  In addition, a maintenance counter that counts the number of sheets passed at a predetermined position may be further provided, and the control unit may be configured to increment the maintenance counter when executing the smoothing process. In this configuration, when the smoothing process is executed, at least one operation other than the fixing process among the operations of the members involved in the image formation is stopped or decelerated, so that the members involved in the image formation are deteriorated. Is suppressed. However, the fixing unit operates when the smoothing process is executed. In addition, not all members involved in image formation except for the fixing unit may stop. For this reason, the deterioration of the members involved in the image formation may progress with a small number or at a low speed. Therefore, the life of the members involved in the image formation can be appropriately managed by stepping up the maintenance counter.

  Furthermore, a maintenance counter and a billing counter for counting the number of sheets passed at a predetermined position are further provided, and the control unit increments the maintenance counter and increments the billing counter when executing the smoothing process. It can be configured not to. In this configuration, the life of the members involved in image formation can be properly managed by incrementing the maintenance counter. On the other hand, since an image is not formed in the smoothing process, an appropriate charging process for image formation can be performed by not incrementing the charging counter.

  An image forming method according to the present invention includes a paper transport unit that transports paper, an image carrier, a transfer unit that performs a transfer process for transferring a toner image formed on the image carrier to a paper transported by the paper transport unit, and the paper The image forming apparatus includes an image forming unit that is disposed on the downstream side of the transfer unit in the transport direction and includes a fixing unit that performs a fixing process of heating and pressing the sheet. The image forming method includes a smoothing step for performing a smoothing process for performing a fixing process on a sheet without performing a transfer process under a predetermined condition, and transferring the sheet subjected to the smoothing process to a transfer unit. A transfer step for performing transfer processing and a fixing step for performing fixing processing on the paper subjected to the transfer processing, and in the smoothing step, a paper transport unit and an image forming unit for forming an image on the paper by accompanying the transfer processing At least one of the operations except the fixing process is stopped or decelerated when the smoothing process is executed.

  In this configuration, the smoothing process is performed under a predetermined condition, so that the paper is heated and pressurized without transferring the toner image. Therefore, even if the paper has low surface smoothness, the surface is smooth. It becomes. For this reason, after the smoothing process is performed, the sheet is conveyed again to the transfer unit and the transfer process is performed, whereby the toner transfer rate is improved and the deterioration of the image quality is suppressed. Further, when performing the smoothing process, at least one of the operations of the members involved in the image formation in the case of forming an image on the sheet with the transfer process is stopped or decelerated except for the fixing process. Therefore, deterioration due to wear or the like of members involved in image formation can be suppressed.

  According to the present invention, it is possible to suppress deterioration in image quality due to a decrease in toner transfer rate even in a sheet having low surface smoothness while suppressing deterioration of members involved in image formation.

1 is a schematic front sectional view of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a front view illustrating a schematic configuration of an intermediate transfer unit, where (A) illustrates a state during non-image formation, (B) illustrates a state during monochrome image formation, and (C) illustrates a state during color image formation. Show. 1 is a block diagram illustrating a schematic configuration of an image forming apparatus. It is a flowchart which shows an example of the process sequence of a control part. (A) and (B) are diagrams showing the state of a creased sheet.

  Embodiments of the present invention will be described below with reference to the drawings.

  As shown in FIG. 1, the image forming apparatus 100 forms a multi-color or single-color image on a predetermined sheet based on image data read from a document. As paper, in addition to paper with high surface smoothness such as plain paper and thick paper, paper with rough eyes, embossed paper whose surface is intentionally embossed, and folded into two or three are used. Examples thereof include paper having low surface smoothness, such as form paper. For example, cardboard used for weddings, event invitations, and the like is shipped in a folded state at the paper making stage, and the image forming apparatus 100 can form an image on such a folded sheet. .

  The image forming apparatus 100 includes an image reading unit 120, an image forming unit 110, a paper feed unit 80, a paper discharge unit 90, and a control unit 200. The control unit 200 comprehensively controls each unit of the image forming apparatus 100.

  The image reading unit 120 generates image data by irradiating the image surface of the document with light and detecting the amount of reflected light.

  The image forming unit 110 includes four image forming stations 30A, 30B, 30C, and 30D, an intermediate transfer unit 40, a secondary transfer unit 50, an exposure unit 60, and a fixing unit 70.

  The intermediate transfer unit 40 includes an intermediate transfer belt 41 that is an endless belt, a first stretching roller 42, a second stretching roller 43, and a tension roller 44. The first tension roller 42, the second tension roller 43, and the tension roller 44 stretch the intermediate transfer belt 41. As an example, the first stretching roller 42 is a driving roller, and the second stretching roller 43 is a driven roller.

  The tension roller 44 is urged by a spring (not shown) in a direction in which it is pressed against the inner peripheral surface of the intermediate transfer belt 41. The tension roller 44 adjusts the tension of the intermediate transfer belt 41.

  The image forming stations 30 </ b> A to 30 </ b> D perform electrophotographic image forming processing using toners of black, cyan, magenta, and yellow hues, respectively. The image forming stations 30 </ b> A to 30 </ b> D are arranged side by side so as to face a predetermined area of the intermediate transfer belt 41. The image forming stations 30B to 30D are configured in the same manner as the image forming station 30A.

  The image forming station 30A includes a monochrome photosensitive drum 31A carrying black toner. The image forming stations 30B, 30C, and 30D include color photosensitive drums 31B, 31C, and 31D that carry color toners, respectively. Each of the photoreceptor drums 31A to 31D constitutes an image carrier.

  The image forming station 30A includes a charging device 32A, a developing device 33A, a primary transfer roller 34A, and a cleaner device 35A around the photosensitive drum 31A. Similarly, the image forming stations 30B, 30C, and 30D have primary transfer rollers 34B, 34C, and 34D, respectively.

  The photosensitive drum 31A rotates in a predetermined direction by receiving a driving force from a driving source (not shown). The charger 32A charges the peripheral surface of the photosensitive drum 31A to a predetermined potential.

  The exposure unit 60 drives the semiconductor laser based on the image data of each hue of black, cyan, magenta, and yellow, and distributes the laser beam of each hue to the respective photosensitive drums 31A to 31D of the image forming stations 30A to 30D. Shine. Electrostatic latent images based on image data of each hue of black, cyan, magenta, and yellow are formed on the peripheral surfaces of the photosensitive drums 31A to 31D.

  The developing device 33A supplies black toner, which is the hue of the image forming station 30A, to the peripheral surface of the photosensitive drum 31A, and visualizes the electrostatic latent image into a toner image.

  The outer peripheral surface of the intermediate transfer belt 41 faces the photosensitive drums 31A to 31D in order. A primary transfer roller 34A is disposed at a position facing the photosensitive drum 31A across the intermediate transfer belt 41. A primary transfer roller 34B is disposed at a position facing the photosensitive drum 31B with the intermediate transfer belt 41 interposed therebetween. A primary transfer roller 34C is disposed at a position facing the photosensitive drum 31C with the intermediate transfer belt 41 interposed therebetween. A primary transfer roller 34D is disposed at a position facing the photosensitive drum 31D with the intermediate transfer belt 41 interposed therebetween.

  By applying a primary transfer bias to the primary transfer roller 34A with a toner charge polarity (for example, minus) and a reverse polarity (for example, plus), the toner image carried on the photosensitive drum 31A is transferred to the outer periphery of the intermediate transfer belt 41. A primary transfer process for transferring to the surface is performed. As a result, the toner image is carried on the outer peripheral surface of the intermediate transfer belt 41. In this embodiment, the intermediate transfer belt 41 constitutes an image carrier. Each of the areas where the photosensitive drums 31A to 34D and the primary transfer rollers 34A to 34D face each other is a primary transfer area.

  The toner remaining on the outer peripheral surface of the photosensitive drum 31A is removed by the cleaner device 35A.

  When forming a monochrome image, the above-described image forming process is performed only by the monochrome image forming station 30A. In addition, when forming a full-color image, the image forming station 30B to 30D in addition to the image forming station 30A performs the same image forming process as the image forming station 30A for each hue of cyan, magenta, and yellow. A toner image of each hue of black, cyan, magenta, and yellow is applied to the outer peripheral surface of the intermediate transfer belt 41 by applying a primary transfer bias to the primary transfer rollers 34A to 34D of the image forming stations 30A to 30D. The images are sequentially transferred so as to be superimposed on each other.

  The paper feed unit 80 includes a paper feed cassette 81, a manual feed tray 82, a paper main transport path 83, a paper sub-transport path 84, a plurality of transport roller pairs 87A, 87B, 87C, and a registration roller pair 88. The paper feed cassette 81 stores a plurality of sheets of a size and type that are relatively frequently used. On the manual feed tray 82, paper of a size or type that is relatively infrequently used is placed. The paper stored in the paper feed cassette 81 is fed to the main paper transport path 83 by the paper feed roller 85. The paper placed on the manual feed tray 82 is fed to the main paper transport path 83 by the paper feed roller 86.

  The paper main conveyance path 83 is discharged from the paper feed cassette 81 and the manual feed tray 82 via the secondary transfer area, which is an area where the intermediate transfer belt 41 and the secondary transfer unit 50 face each other, and the fixing unit 70. It is formed to reach part 90. The sheet sub-transport path 84 is a sheet transport path for double-sided image formation, and branches from the sheet main transport path 83 on the downstream side of the fixing unit 70 in the sheet transport direction, and on the upstream side of the secondary transfer region. It is formed so as to join the conveyance path 83. The paper that has passed through the secondary transfer area and the fixing unit 70 is transported through the paper sub-transport path 84, and is transported again to the secondary transfer area with the front and back reversed.

  The registration roller pair 88 is disposed on the upstream side of the secondary transfer region in the sheet conveyance direction. The registration roller pair 88 performs paper conveyance control. Specifically, the registration roller pair 88 corrects the oblique feeding of the sheet by being abutted on the sheet conveyed through the sheet main conveyance path 83 in a state where the rotation is stopped. The registration roller pair 88 conveys the sheet to the secondary transfer region at a predetermined timing so that the leading end of the toner image carried on the intermediate transfer belt 41 and the leading end of the sheet are aligned.

  The secondary transfer unit 50 includes a secondary transfer roller 50A. A toner image carried on the outer peripheral surface of the intermediate transfer belt 41 is applied to the secondary transfer roller 50 </ b> A by applying a secondary transfer bias having a toner charging polarity (for example, minus) and a reverse polarity (for example, plus). A secondary transfer process for secondary transfer to the paper is performed.

  The intermediate transfer unit 40, the primary transfer rollers 34A to 34D, and the secondary transfer unit 50 constitute a transfer unit that transfers the toner images carried on the photosensitive drums 31A to 31D to a sheet.

  The fixing unit 70 includes a fixing roller 71 and a pressure roller 72, and is disposed on the downstream side of the secondary transfer region in the sheet conveyance direction. The pressure roller 72 is in pressure contact with the fixing roller 71. The pressure roller 72 is configured to be able to change the setting of the pressing force. The pressure applied by the pressure roller 72 is controlled by the control unit 200. The fixing unit 70 performs a fixing process in which the paper is conveyed between the fixing roller 71 and the pressure roller 72 while being heated and pressed. The paper on which the toner image has been transferred is heated and pressurized, so that the toner image is fixed on the paper. The fixing unit 70 constitutes a fixing unit.

  The paper discharge unit 90 includes a paper discharge tray 91 and a paper discharge roller 92. The sheet on which the toner image has been fixed is discharged to a discharge tray 91 by a discharge roller 92. The paper is stored in the paper discharge tray 91 with the surface on which the toner image is fixed facing down.

  The paper feed unit 80 and the paper discharge unit 90 constitute a paper transport unit that transports paper.

  As shown in FIGS. 2A to 2C, the intermediate transfer belt 41 is stretched between a first stretching roller 42 and a second stretching roller 43 to move in a predetermined loop shape. Configure the route. The photosensitive drum 31D, the photosensitive drum 31C, and the photosensitive drum 31B are sequentially arranged from the upstream side in the moving direction 93 of the intermediate transfer belt 41 in the region facing the photosensitive drums 31A to 31D along the outer peripheral surface of the intermediate transfer belt 41. And a photosensitive drum 31A. In the moving direction 93, the first stretching roller 42 is disposed on the downstream side, and the second stretching roller 43 is disposed on the upstream side. As described above, the primary transfer rollers 34A to 34D are arranged at positions facing the photosensitive drums 31A to 31D with the intermediate transfer belt 41 interposed therebetween.

  The primary transfer rollers 34 </ b> A to 34 </ b> D are configured to be displaceable in the direction of separating from and contacting the photosensitive drums 31 </ b> A to 31 </ b> D that face each other. Accordingly, the primary transfer roller 34A is displaceable between a pressing position where the intermediate transfer belt 41 is pressed against the opposing photosensitive drum 31A and a separation position where the intermediate transfer belt 41 is separated from the opposing photosensitive drum 31A. . The primary transfer rollers 34B to 34D are the same as the primary transfer roller 34A.

  As shown in FIG. 2A, at the time of non-image formation, all of the primary transfer rollers 34A to 34D are arranged at the respective separated positions, so that the intermediate transfer belt 41 is separated from all the photosensitive drums 31A to 31D. Arranged at predetermined spaced apart non-image forming positions.

  As shown in FIG. 2B, at the time of monochrome image formation, the monochrome primary transfer roller 34A is arranged at the pressing position, and the color primary transfer rollers 34B to 34D are arranged at the separated positions. The intermediate transfer belt 41 is disposed at a monochrome image forming position separated from the color photosensitive drums 31B to 31D while being in pressure contact with only the monochrome photosensitive drum 31A.

  As shown in FIG. 2C, at the time of color image formation, the primary transfer rollers 34A to 34D are arranged at the pressing positions, so that the intermediate transfer belt 41 is placed on all the photosensitive drums 31A to 31D. It is arranged at the color image forming position that is in pressure contact.

  The arrangement of the intermediate transfer belt 41 is controlled by the control unit 200.

  As shown in FIG. 3, the image forming apparatus 10 further includes an operation unit 201, a display unit 202, a maintenance counter 203, a charging counter 204, and an image input unit 205.

  The operation unit 201 receives various input operations such as the type of paper on which an image is formed and an image formation mode, and outputs the input operation to the control unit 200. The display unit 202 displays various information. The operation unit 201 and the display unit 202 can constitute a touch panel that can perform an input operation on the operation screen.

  The image input unit 205 receives image data output from an externally connected information processing apparatus or recording medium, or image data generated by the image reading unit 120. The image forming conditions are input from the operation unit 201 or from the image input unit 205 together with the image data. As image formation conditions, setting of paper size, setting of single-sided printing or double-sided printing, setting of monochrome image formation or color image formation, setting of whether to perform smoothing processing, etc. Is mentioned. The smoothing process is set so as to be executed when the paper is a paper with low smoothness such as a creased paper such as an invitation or a paper with a large surface unevenness such as an embossed paper.

  The maintenance counter 203 and the billing counter 204 each count the number of sheets that have passed through at predetermined positions. The maintenance counter 203 is for performing proper life management of members involved in image formation. The accounting counter 204 is for performing an appropriate accounting process for image formation. The control unit 200 can step and stop the maintenance counter 203 and the billing counter 204, respectively. During normal image formation, both the maintenance counter 203 and the billing counter 204 are incremented for each sheet of paper.

  When the image data is input from the image input unit 205, the control unit 200 controls the load devices of the image forming unit 110 such as the paper transport unit 206 and the transfer unit 207 and the fixing unit 70 based on the image forming conditions. Then, an image is formed on the paper.

  As shown in FIG. 4, when a print job is input (S1), the control unit 200 determines whether or not the smoothing process is set based on the image forming conditions (S2).

  When the control unit 200 is set to execute the smoothing process, the control unit 200 performs a predetermined stop deceleration setting (S3). The stop deceleration setting excludes the fixing process from the operations of the members included in the sheet conveying unit 206 and the image forming unit 110 when the image is formed on the sheet by the transfer process, that is, the operations of the members involved in the image formation. At least one of the operations is stopped or decelerated. Specifically, as the stop deceleration setting, (A) the intermediate transfer belt 41 is not moved to the monochrome image forming position and the color image forming position, but is arranged at a non-image forming position separated from all the photosensitive drums 31A to 31D. (B) Stop or decelerate the rotation of the photosensitive drums 31A to 31D. (C) Do not perform sheet conveyance control by the registration roller pair 88, and move the sheet at a predetermined speed like the conveyance roller pair 87A to 87C. (D) Phase control for adjusting the position of the toner image on the intermediate transfer belt 41 is not performed. As the stop deceleration setting, at least one predetermined among the above (A) to (D) is adopted.

  Of the above stop deceleration settings, (B) it is preferable to stop or decelerate the photosensitive drums 31A to 31D.

  The control unit 200 includes the setting for executing the smoothing process in the image forming condition, and executes the smoothing process when the stop deceleration setting is performed (S4). The smoothing process is a process for performing a fixing process for heating and pressurizing the paper without performing a transfer process for transferring the toner images carried on the photosensitive drums 31 </ b> A to 31 </ b> D to the paper conveyed by the paper conveying unit 206. is there. In this embodiment, when executing the smoothing process, the control unit 200 does not form electrostatic latent images on the photosensitive drums 31 </ b> A to 31 </ b> D by the exposure unit 60 and feeds paper. It passes through the next transfer area and is conveyed to the fixing unit 70. That is, during the smoothing process, toner images are not formed on the photoconductive drums 31A to 31D, and therefore the transfer process is not performed.

  As shown in an example in FIGS. 5A and 5B, when a sheet having low smoothness is conveyed to the fixing unit 70, the sheet is sandwiched between the fixing roller 71 and the pressure roller 72. It is conveyed while being heated and pressurized. As a result, the crease marks are erased or the surface roughness of the sheet is reduced.

  When performing the smoothing process, the smoothness of the paper is achieved by performing at least one of a reduction in the paper conveyance speed, an increase in the set temperature of the fixing unit 70, and an increase in the pressure applied in the fixing unit 70. Can be further improved.

  Specifically, when the smoothing process is executed, the conveyance speed of the paper that passes through the fixing unit 70 is made lower than the conveyance speed when the toner image is transferred to the paper and image formation is performed. As a result, it is possible to lengthen the time for performing the fixing process on the paper, so that the smoothness of the paper can be further improved. Further, the heating temperature in the fixing unit 70 is set higher than the heating temperature in the fixing unit 70 when an image is formed by transferring a toner image onto a sheet. Accordingly, the paper can be pressurized while being heated at a higher temperature, so that the smoothness of the paper can be further improved. Further, the pressing force in the fixing unit 70 is improved as compared with the pressing force in the fixing unit 70 when the toner image is transferred to a sheet and image formation is performed. Accordingly, the paper can be heated while being pressed with a larger force, so that the smoothness of the paper can be further improved.

  By performing the smoothing process on the paper having a low surface smoothness, the surface smoothness of the paper can be improved, and the surface of the paper is sufficiently brought into contact with the intermediate transfer belt 41 in the secondary transfer region. Therefore, it is possible to improve the toner transfer rate and suppress deterioration of image quality.

  In addition, when executing the smoothing process, at least one of the operations of the members involved in image formation except for the fixing process is stopped or decelerated and stopped or decelerated. It is possible to suppress deterioration due to wear or the like of the members to be performed, that is, the photosensitive drums 31A to 31D, the intermediate transfer belt 41, the registration roller pair 88, and the like.

  The paper that has passed through the fixing unit 70 during the smoothing process is switched back with the trailing edge held between the paper discharge rollers 92, so that the paper is sent to the paper sub-transport path 84, and the transport roller pair 87 </ b> B, It is transported by 87C and supplied again to the secondary transfer area in a state where the front and back sides are reversed.

  The image forming condition can be configured to include information on the number of times the smoothing process is set. The information on the number of execution times of the smoothing processing can be configured so that it can be set for each print job, and can also be configured so that it can be set for each sheet.

  The control unit 200 executes a smoothing process in which the fixing unit 70 performs the fixing process by passing the secondary transfer area without performing the transfer process, and the sheet is conveyed again to the secondary transfer area via the paper sub-transport path 84. This process is performed as many times as the number of executions of the smoothing process (S5). By repeating the smoothing process a plurality of times, the smoothness of the surface of the paper can be further improved.

  When executing the smoothing process for the number of times of setting execution, the control unit 200 changes the setting made in the stop deceleration setting in step S3 to the setting for performing normal image formation (S6). Thereafter, the control unit 200 transfers the toner image onto the sheet in the secondary transfer region, and fixes the toner image on the sheet with the fixing unit 70, thereby forming an image on the sheet (S7). The control unit 200 repeats the above-described processes from S2 to S7 until the print job is completed, and waits for the input of a new print job when the print job is completed (S8).

  The control unit 200 can be configured not to execute the image quality adjustment process even when the execution time of the image quality adjustment process arrives during the smoothing process. Accordingly, the smoothing process can be completed in a short time, so that the image formation can be completed at an early stage.

  When executing the smoothing process, the control unit 200 increments the maintenance counter 203 and does not increment the accounting counter 204.

  In the image forming apparatus 100, when the smoothing process is executed, the stop deceleration setting is performed, and at least one of the operations of the members related to the image formation except the fixing process is stopped or decelerated. Deterioration of members involved in image formation is suppressed. However, the fixing unit 70 also operates when executing the smoothing process. In addition, not all the members involved in image formation except for the fixing unit 70 may stop. For this reason, deterioration of the members involved in the image formation may progress with a small number or at a low speed, so that the life of the members involved in the image formation can be appropriately managed by stepping up the maintenance counter 203. .

  Further, since an image is not formed in the smoothing process, an appropriate charging process for image formation can be performed by not incrementing the charging counter 204.

  Since the transfer unit 207, the fixing unit 70, the paper transport unit 206, and the like of the image forming unit 110 are normally configured in an image forming apparatus such as a multifunction peripheral as a standard, the image forming apparatus only needs to change firmware. The embodiment according to the present invention can be easily implemented without increasing the cost.

  The above description of the embodiment is to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown not by the above embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

31A to 31D Photosensitive drum (image carrier)
34A to 34D Primary transfer roller 40 Intermediate transfer unit 41 Intermediate transfer belt 50 Secondary transfer unit 50A Secondary transfer roller 70 Fixing unit (fixing unit)
83 Paper main transport path 84 Paper sub transport path 88 Registration roller pair 100 Image forming apparatus 110 Image forming unit 200 Control unit 203 Maintenance counter 204 Billing counter 206 Paper transport unit 207 Transfer unit

Claims (7)

A paper transport unit for transporting paper,
An image carrier, a transfer unit that performs a transfer process for transferring a toner image carried on the image carrier to a sheet conveyed by the sheet conveyance unit, and a sheet disposed downstream of the transfer unit in the sheet conveyance direction An image forming unit having a fixing unit for performing a fixing process of heating and pressing
A control unit that controls operations of the paper transport unit and the image forming unit, and performs a smoothing process that performs the fixing process on the paper without performing the transfer process under a predetermined condition,
The control unit performs at least one of the operations of the sheet transport unit and the image forming unit excluding the fixing process when the image is formed on the sheet with the transfer process, by the smoothing process. An image forming apparatus which is stopped or decelerated when executing the above. The paper transport unit includes a transport path for transporting the paper subjected to the fixing process in the fixing unit to the transfer unit again.
The image forming apparatus according to claim 1, wherein the control unit performs the transfer process by conveying the sheet to the transfer unit again after executing the smoothing process a plurality of times under the predetermined condition. The fixing unit is configured to be able to change the setting of the pressing force,
The image forming apparatus according to claim 1, wherein the control unit improves a pressing force in the fixing unit when performing the smoothing process.   4. The image forming apparatus according to claim 1, wherein the control unit does not execute the image quality adjustment process even when the execution time of the image quality adjustment process comes during execution of the smoothing process. A maintenance counter that counts the number of sheets passed at a predetermined position;
The image forming apparatus according to claim 1, wherein the control unit increments the maintenance counter when executing the smoothing process. A maintenance counter and a billing counter for counting the number of sheets passed through at a predetermined position;
The image forming apparatus according to claim 1, wherein the control unit increments the maintenance counter and does not increment the billing counter when executing the smoothing process. A sheet conveying unit that conveys the sheet, an image carrier, a transfer unit that performs a transfer process for transferring a toner image formed on the image carrier to the sheet conveyed by the sheet conveying unit, and the transfer unit in the sheet conveying direction An image forming method that is executed in an image forming apparatus that includes a fixing unit that is disposed on the downstream side of the image forming unit and that has a fixing unit that performs a fixing process for heating and pressurizing paper.
A smoothing step for performing a smoothing process for performing the fixing process on a sheet without performing the transfer process under a predetermined condition;
A transfer step of transporting the paper subjected to the smoothing process to the transfer unit and performing the transfer process;
A fixing step of performing the fixing process on the paper subjected to the transfer process,
In the smoothing step, at least one of the operations of the paper transport unit and the image forming unit excluding the fixing process when the image is formed on the paper by accompanying the transfer process, the smoothing is performed. An image forming method in which processing is stopped or slowed down.

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