Image forming apparatus

Abstract

To achieve a further reduction in downtime of an image forming apparatus.SOLUTION: An image forming apparatus 100 has: an image forming unit for image carriers 2; primary transfer units 19 that transfer images to an intermediate transfer body 16; a secondary transfer unit 20 that transfers the images to a sheet; a cleaning unit 21 that cleans the intermediate transfer body 16; a feeding unit that feeds the sheet; a determination unit 108 that determines whether a feeding time for feeding the sheet to the secondary transfer unit 20 exceeds a predetermined time; and a retry control unit 107 that, when the feeding time exceeds the predetermined time, controls an image formation timing and a sheet feeding timing so that the positions of the images and sheet match each other in the secondary transfer unit. When the feeding time exceeds the predetermined time, image formation on the image carriers is suspended and subsequently resumed. The inter-image distance in a white paper part between a suspended image to be removed by the cleaning unit and an image to be re-formed is the product of the separation time of the secondary transfer unit and a process linear velocity. When the suspended image passes through the secondary transfer unit, the secondary transfer unit is separated from the intermediate transfer body.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an image forming apparatus.

Background Art

[0002] In an image forming apparatus, when a delay occurs in paper conveyance, a technique (retry control) for interrupting the paper conveyance and retransmitting an image is already known.

[0003] However, in the conventional retry control, the distance (distance between images) between the image to be reformed and retransmitted and the interrupted image that has been previously formed is not defined.

[0004] Patent Document 1 discloses a retry control for retransmitting an image when the feeding time exceeds a predetermined time in order to prevent the occurrence of downtime required for removing jammed paper and to prevent waste of paper.

[0005] However, since the distance (distance between images) between the retransmitted image and the interrupted image that has been previously formed is not defined, the downtime still becomes long.

Summary of the Invention

Problems to be Solved by the Invention

[0006] Therefore, an object of the present invention is to further reduce the downtime of an image forming apparatus.

Means for Solving the Problems

[0007] This problem is related to an image forming apparatus having an image forming unit that forms an image on an image carrier, a primary transfer unit that transfers the image formed on the image carrier to an intermediate transfer body, a secondary transfer unit that transfers the image transferred to the intermediate transfer body to a recording medium, a cleaning unit that cleans the intermediate transfer body, a feeding unit that feeds the recording medium from a storage unit where the recording medium is stored to the secondary transfer unit, a determination unit that determines whether a feeding time for feeding the recording medium to the secondary transfer unit exceeds a predetermined time, and a retry control unit that controls a timing of forming the image on the image carrier in the image forming unit and a timing of feeding the recording medium in the feeding unit so that a position between the image formed on the image carrier and the recording medium matches at the secondary transfer unit when the feeding time exceeds the predetermined time. In the image forming apparatus, when the feeding time exceeds the predetermined time, formation of the image on the image carrier is interrupted, and then formation of the image on the image carrier is resumed. The image reformed on the intermediate transfer member is conveyed to the secondary transfer portion together with the interrupted image, and the secondary transfer portion is separated from the intermediate transfer member before the interrupted image passes through the secondary transfer portion. After the interrupted image passes through the secondary transfer portion and the cleaning portion and before the reformed image passes through the secondary transfer portion, the secondary transfer portion is brought into contact with the intermediate transfer member. The time from when the secondary transfer portion is separated from the intermediate transfer member until it comes into contact with the intermediate transfer member is the separation time. An image interval distance of a blank paper portion between an interrupted image removed in the cleaning unit and an image re-formed on the intermediate transfer body is The the product of an interval time from the intermediate transfer body in the secondary transfer unit and a process line speed. of This is solved by an image forming apparatus characterized by this.

Effects of the Invention

[0008] Downtime of the image forming apparatus can be further reduced.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0010] [Configuration of Image Forming Apparatus] First, the image forming apparatus according to the present embodiment will be described with reference to the drawings. The image forming apparatus according to the present embodiment uses media such as paper, OHP sheets, threads, fibers, fabrics, leather, metals, plastics, glass, wood, and ceramics as "recording media", and is an apparatus that forms an image by attaching a developer or ink to this storage medium. In the following description, "image formation" not only refers to imparting an image having a meaning such as characters or figures to a recording medium, but also includes imparting an image having no meaning such as a pattern to a recording medium. Also, the "sheet-like body" is not limited to paper (printing paper), but also includes OHP sheets, fabrics, etc., and means a medium to which a developer or ink can be attached, and also includes those referred to as a recording medium, a recording medium, recording paper, printing paper, etc. In the following embodiments, the sheet-like body will be described as "paper P". Also, the dimensions, materials, shapes, relative arrangements, etc. described in the explanations of each component are examples, and are not intended to limit the scope of the present invention to them unless otherwise specifically stated.

[0011] FIG. 1 is a configuration diagram showing an embodiment of an image forming apparatus including an image forming control apparatus according to the present invention, and is a configuration diagram showing an example of a tandem type color laser printer (hereinafter simply referred to as "printer 100") in which a plurality of image carriers 2 are arranged in parallel. As shown in FIG. 1, inside the printer 100, four process units 1C, 1M, 1Y, and 1K are arranged as image forming units (image forming apparatuses) for forming images of respective colors of cyan (C), magenta (M), yellow (Y), and black (K). The four process units 1 (C, M, Y, K) have substantially the same configuration except that the toner colors are different. In the following description, for convenience, C (cyan), M (magenta), Y (yellow), and K (black) will be appended as subscripts corresponding to the toner colors of the images to be formed behind the numbers indicating the constituent members. In the case of general descriptions, these subscripts will be omitted as appropriate.

[0012] As shown in FIG. 1, each of the process units 1 (C, M, Y, K) includes a drum-shaped image carrier 2 (2C, 2M, 2Y, 2K). These four image carriers 2 are arranged in parallel at equal intervals in the moving direction of the intermediate transfer belt 16 in the image forming unit. Each of the image carriers 2 rotates the peripheral surface in the same direction as the conveyance direction of the opposing intermediate transfer belt 16 when the printer 100 operates, by having drive transmitted from a drive source. A toner image is formed on the image carrier 2 by an image forming process using laser light inside the process unit 1.

[0013] A transfer device 15 is arranged below the image carrier 2. This transfer device 15 has an endless intermediate transfer belt 16. One end of the intermediate transfer belt 16 is wound around a driven roller 17, and the other end is wound around a transfer drive roller 18. When the transfer drive roller 18 driven by a drive source rotates, the intermediate transfer belt 16 travels in the direction of arrow A, and the surface of each image carrier 2 comes into contact with the upper surface of the intermediate transfer belt 16. Four primary transfer rollers 19 (C, M, Y, K), which are primary transfer portions, are provided on the inner peripheral portion of the intermediate transfer belt 16, which is an intermediate transfer member, so as to face each image carrier 2.

[0014] Near the right end of the outer periphery of the intermediate transfer belt 16, a belt cleaning device 21 that constitutes a cleaning unit is provided. The belt cleaning device 21 is a device that wipes away unnecessary toner remaining on the surface of the intermediate transfer belt 16 and foreign substances such as paper dust.

[0015] On the outer periphery of the intermediate transfer belt 16, at a position facing the transfer drive roller 18 with the intermediate transfer belt 16 interposed therebetween, a secondary transfer roller 20 that constitutes a secondary transfer unit is provided. The secondary transfer roller 20 abuts on the intermediate transfer belt 16 at a position facing the transfer drive roller 18, and forms a secondary transfer nip as a secondary transfer unit. In the secondary transfer nip, while passing the paper P, which is a recording medium, between the intermediate transfer belt 16 and the secondary transfer roller 20, an electrostatic charge is applied to transfer the toner image formed and carried on the intermediate transfer belt 16 onto the paper P electrostatically.

[0016] The paper feed tray 30 is a storage unit that stores a plurality of sheets of paper P stacked in its internal space. On the bottom surface of the internal space of the paper feed tray 30, a bottom plate 46 for placing the paper P in a stacked state is disposed. One end of the bottom plate 46 in the longitudinal direction is rotatably supported by a support shaft, and the other end is swingable in the vertical direction. And the bottom plate 46 is constantly biased upward by a biasing member such as a spring.

[0017] A paper feed roller 47 as a rotating member is disposed on the paper feed tray 30 on the end side where the bottom plate 46 swings. This paper feed roller 47 abuts on the top of the bundle of sheets of paper P placed on the paper feed tray 30 in a stacked state, and can feed out the top sheet of paper P. Since the paper feed roller 47 only needs to be able to feed the paper P in a predetermined direction, it does not necessarily have to be in the form of a roller. For example, instead of the paper feed roller 47, an endless rotating belt stretched between two rollers may be used.

[0018] Downstream of the paper feed roller 47 in the paper feed direction, a registration sensor 31 capable of detecting the leading edge of the sheet P is disposed. Further downstream of the registration sensor 31 in the paper feed direction, a registration roller pair 32, which is a medium standby unit for temporarily stopping the sheet P, is disposed. The registration roller pair 32 is located immediately upstream of the intermediate transfer belt 16. In order to accurately align the toner image carried on the intermediate transfer belt 16 with the leading edge position of the sheet at the transfer unit, the sheet P is temporarily stopped and relaxed. The registration roller pair 32 feeds out the sheet P that has been temporarily stopped at a predetermined timing to the secondary transfer nip portion immediately before the toner image formed and carried on the intermediate transfer belt 16 is transferred to the sheet P at the secondary transfer nip portion. The paper feed unit is constituted by the paper feed tray 30, the paper feed roller 47, and the registration roller pair 32.

[0019] Upstream of the secondary transfer nip portion formed by the secondary transfer roller 20 and the transfer driving roller 18 in the paper feed direction, a fixing device 34 is disposed. The fixing device 34 includes a fixing roller 34a that incorporates a heat source such as a halogen lamp, and a pressure roller 34b that rotates while contacting the fixing roller 34a with a predetermined pressure. Note that the fixing device 34 may adopt other configurations such as an endless rotating belt or an IH heating method.

[0020] [Basic Operation of Printer] Next, the basic operation of the printer 100 will be described. In FIG. 1, when the paper feed roller 47 of the paper feed tray 30 rotates according to a paper feed start signal from the printer control unit, only the uppermost sheet P stacked on the bottom plate 46 of the paper feed tray 30 is separated from the lower sheets P and fed out.

[0021] When the leading edge of the sheet P is detected by the registration sensor 31, the sheet P is fed until a predetermined slack is formed at the secondary transfer nip portion of the registration roller pair 32 using the feed timing as a trigger, and the leading edge skew of the sheet P is corrected.

[0022] Next, the image forming operation of the printer 100 will be described. The visible image formed on the image carrier 2K is primarily transferred onto the surface of the intermediate transfer belt 16 that moves in synchronization with the image carrier 2K by the transfer action of the positively charged primary transfer roller 19K. All of the operations of latent image formation, development, and primary transfer are sequentially performed in synchronization with the image data in all of the process units 1 (C, M, Y, K), and a four-color toner image in which cyan C, magenta M, yellow Y, and black K toner images are sequentially overlapped is carried on the surface of the intermediate transfer belt 16. This four-color toner image is conveyed together with the intermediate transfer belt 16 that moves on the surface in the direction of arrow A.

[0023] When each color toner image is transferred onto the intermediate transfer belt 16, the registration roller pair 32 and the paper feed roller 47 start driving, and the sheet P is fed to the secondary transfer roller 20 at the transfer position so as to be in timing with the toner image transferred onto the intermediate transfer belt 16. Note that the start of driving of the registration roller pair 32 and the paper feed roller 47 does not necessarily have to be simultaneous. Also, there may be a paper feed roller that feeds the sheet P in addition to the registration roller pair 32 and the paper feed roller 47. The secondary transfer roller 20 is positively charged, and the toner image on the intermediate transfer belt 16 is transferred onto the fed sheet P by the secondary transfer nip portion of the secondary transfer roller 20. Residual toner and foreign matter on the surface of the intermediate transfer belt 16 are removed by the belt cleaning device 21 for the next image forming / transferring process.

[0024] After the toner image is transferred, the sheet P is sent to the fixing device 34. The sheet P fed into the fixing device 34 is sandwiched between the fixing roller 34a and the pressure roller 34b, and the unfixed toner image is heated and pressurized to be fixed onto the sheet P.

[0025] [Hardware Configuration of Image Forming Apparatus] Next, the hardware configuration that controls the control system of the image forming apparatus according to the present embodiment will be described with reference to FIG. 2. The hardware configuration of the image forming apparatus shown in FIG. 2 is exemplified as being applied to the printer 100.

[0026] As shown in FIG. 2, the image forming control apparatus according to the present embodiment includes a UART (Universal Asynchronous Receiver Transmitter) 57, a CPU (Central Processing Unit) 58, a ROM (Read Only Memory) 59, a RAM (Random Access Memory) 60, an NVRAM (NonVolatie Random Access Memory) 61, an operation panel I / F 62, an I / O 65, and an image processing IC 66, which are interconnected via a system bus 64. The ROM 59, the RAM 60, and the NVRAM 61 constitute a storage unit of the printer 100 according to the present embodiment.

[0027] An operation panel 63 operated by a user is connected to the operation panel I / F 62, and a controller 67 is connected to the image processing IC 66. Further, a registration sensor 31 for detecting that a sheet P is being fed, a feed motor 69 for rotationally driving a paper feed roller 47, a transfer motor 70 for rotationally driving a transfer driving roller 18, a photoreceptor motor 71 for rotationally driving an image carrier 2, and a temperature and humidity sensor 72 for selecting the temperature and humidity of the sheet P are connected to the I / O 65.

[0028] The operation panel 63 is connected to the CPU 58 via the operation panel I / F 62. The operation panel 63 includes a display unit and an input unit, functions as a user interface, and is used for settings such as a printer mode. The operation panel I / F 62 performs data exchange between the CPU 58 and the operation panel 63. Further, the controller 67 is connected to the CPU 58 via the image processing IC 66. The CPU 58 acquires printing conditions such as the paper thickness of the paper to be printed from the controller 67.

[0029] The CPU 58 is a control unit that controls the entire image forming apparatus, and comprehensively controls access to various devices connected to the system bus 64 based on a control program and the like stored in the ROM 59. The CPU 58 controls the input / output of the resist sensor 31, the feeding motor 69, the transfer motor 70, the photoreceptor motor 71, and the temperature and humidity sensor 72 connected via the I / O 65. That is, the CPU 58 executes the control program of the image forming apparatus stored in the ROM 59.

[0030] The CPU 58 follows instructions composed of a control program, control data, etc., and performs control related to image forming processes such as measurement of the feeding time of the paper P, detection of a delay in the feeding time, image reformation, resist restart (re - feeding). That is, the CPU 58 executes control related to image forming processes such as measurement of the feeding time of the paper P, detection of a delay in the feeding time, image reformation, resist restart (re - feeding).

[0031] The ROM 59 is a read - only non - volatile memory, and stores a control program, control data, etc. used by the CPU 58.

[0032] The RAM 60 is a volatile memory capable of high - speed reading and writing of information, and is used as a work frame memory for developing recording data and storing environmental data.

[0033] The NVRAM 61 is a non - volatile memory capable of reading and writing, and stores information related to the image forming apparatus used by the control program.

[0034] [Functional Configuration of Printer 100] Next, the functional configuration of the printer 100 will be described. As shown in FIG. 3, the printer 100 includes a control unit 101, an image forming process unit 102, a fixing unit 103, an image writing control unit 104, an operation unit 105, an I / F unit 106, a retry control unit 107, a determination unit 108, and a resist monitoring unit 109.

[0035] The control unit 101 controls a series of operations in each of the above - mentioned functional blocks.

[0036] The image forming process unit 102 creates a toner image by an electrophotographic method from the image data transmitted from the terminal device and transfers it to the paper P. Further, when the image forming process unit 102 detects misregistration during printing, it corrects it.

[0037] The fixing unit 103 applies heat and pressure to the paper P onto which the toner image has been transferred by the image forming process unit 102 to fix the toner image on the paper.

[0038] The image writing control unit 104 converts the image data transmitted from the I / F unit 106 into control signals for each color provided in the process unit 1 and controls the writing of the latent image on the image carrier 2.

[0039] The operation unit 105 displays the state of the image forming apparatus and accepts inputs to the image forming apparatus.

[0040] The I / F unit 106 communicates with a terminal device that issues a printing request to the printer 100. The I / F unit 106 transmits the image data transmitted from the terminal device to the control unit 101 and issues a printing request to the printer 100.

[0041] The retry control unit 107 controls the image formation timing, paper feed timing, etc. in the image forming process unit 102 and executes a retry process such as re-executing the image forming process. More specifically, when the paper feed time exceeds a predetermined time, the retry control unit 107 controls the image formation timing on the image carrier 2 in the process unit 1 and the paper feed timing of the paper P in the paper feed unit so that the image formed on the image carrier 2 and the paper P coincide at the secondary transfer roller 20.

[0042] The determination unit 108 determines whether or not the paper feed time for feeding the paper P to the secondary transfer roller 20 exceeds a predetermined time.

[0043] The resist monitoring unit 109 monitors the state of the resist sensor 31 after the start of execution of the image forming process in the image forming process unit 102, measures the paper feed time of the paper P, and determines the execution timing of the retry process.

[0044] Figure 4 is a timing chart showing the normal printing (a) and retry control (b) in the printer 100. Here, the main body paper feeding operation, for example, the image formation of the image carrier 2Y which is the yellow photoreceptor, and the timing of the secondary transfer bias are described. However, the same ON / OFF control also applies to the image carriers 2 of other colors.

[0045] In the normal printing of Figure 4(a), T1 in the main body paper feeding operation is the time from the start of yellow image formation to the start of paper feeding by the paper feed roller 47, and T2 in the secondary transfer bias is the time from the start of yellow image formation to the application of the secondary transfer bias. That is, during normal printing, in order to shorten the first copy time, the paper feeding operation is started T1 after the start of yellow image formation. Also, the toner image on the image carrier 2 is transferred onto the intermediate transfer belt 16, and T2 after the start of yellow image formation, it is transferred at the secondary transfer unit to the Nth sheet of paper P that has been conveyed. The timing of the main body paper feeding, yellow image formation, and secondary transfer bias for the (N + 1)th sheet of paper P is the same as that for the Nth sheet of paper P.

[0046] In the retry control in Figure 4(b), after the main body paper feeding operation starts, when it is detected at J1 that the paper feeding time has exceeded the predetermined time and a paper jamming due to non - paper feeding has occurred in the paper feeding unit, the main body paper feeding and yellow image formation of the Nth sheet of paper P are interrupted, and at the timing J2 when the preparation for the next paper feeding start is complete, the retry control is started, that is, the main body paper feeding and yellow image formation of the Nth sheet of paper P are resumed. In Patent Document 1, the image interval corresponding to the time from the detection of the non - paper feeding jam at J1 to the resumption of image formation at J2 (the time until the start of the retry control, which is the waiting time of the user) is not defined. However, in this embodiment, by shortening this image interval, the downtime is reduced.

[0047] Note that the "paper feed jam" includes not only the case where the user cannot re-feed unless the jammed paper in the apparatus is removed, but also the case where slippage occurs in the paper feed roller 47 of the paper feed tray 30 and the paper P is determined to be jammed because it does not reach the registration sensor 31 within a predetermined time. In the latter case, the paper P can be conveyed by rotating the paper feed roller 47 again without removing the paper P.

[0048] FIG. 5 is a schematic diagram showing the printing operations during normal printing (a), retry control (re-feed after pre-image cleaning) (b), and retry control (re-feed before pre-image cleaning) (c) in the printer 100. Here, for convenience, the image carriers 2 of each color are shown outside the intermediate transfer belt 16. During normal printing in FIG. 5(a), the toner image on the intermediate transfer belt 16 and the paper P are conveyed in synchronization (A-1), and the toner image is transferred from the intermediate transfer belt 16 to the paper P by the secondary transfer roller 20 (A-2).

[0049] In the retry control (re-feed after pre-image cleaning) in FIG. 5(b), after the elapse of a predetermined time exceeding the feeding time or after detection of a paper feed jam, the image formation and main body paper feed operations are interrupted and switched to blank paper (B-1). Thereafter, the toner image on the intermediate transfer belt 16 is conveyed to the secondary transfer roller 20 (B-2). At this time, the secondary transfer roller 20 may be separated from the intermediate transfer belt 16 and the secondary transfer bias may be set to GND, or a bias having a polarity opposite to the image portion bias may be applied while the secondary transfer roller 20 is in contact, or the secondary transfer bias may be set to GND. After the toner image on the intermediate transfer belt 16 is cleaned by the cleaning blade of the belt cleaning device 21 (B-3), the image formation and main body paper feed operations are resumed (B-4). Thereafter, the toner image formed on the intermediate transfer belt 16 and the paper P are conveyed in synchronization, and the toner image is transferred from the intermediate transfer belt 16 to the paper P by the secondary transfer roller 20.

[0050] In the retry control of Fig. 5(c) (retransmission after pre-image cleaning), after the predetermined time of the paper feed time has elapsed or after a paper feed jam has been detected, image formation is interrupted and switched to blank paper (C-1). Then, image formation is resumed, and a toner image is re-formed on the secondary transfer belt 16 on the downstream side of the interrupted image. The re-formed image is conveyed to the secondary transfer roller 20 together with the interrupted image (C-2). Although there is a blank paper area (image interval) between the interrupted image and the re-formed image, the image length (image interval) of this blank paper area varies depending on the cleaning conditions required before the next image formation, such as the time required for the secondary transfer roller 20 to move from separation to contact and the cleaning time of the secondary transfer roller 20. In this embodiment, the image interval of the blank paper area between the interrupted image to be removed and the image re-formed on the intermediate transfer belt 16 is equal to the product of the separation time of the secondary transfer roller 20 from the intermediate transfer belt 16 and the process line speed. Thereby, the image interval becomes shorter, and it becomes possible to reduce the downtime.

[0051] Here, the separation time means the time from the separated state where the secondary transfer roller 20 is separated from the intermediate transfer belt 16 to the contacting state where it contacts the intermediate transfer belt 16. More specifically, the separation time is the time from the start of contact to the completion of contact in the separated state. Here, the start of contact is the timing when the secondary transfer roller 20 starts to move from the separated state toward the contacting state, and the completion of contact is the timing when the secondary transfer roller 20 contacts the intermediate transfer belt 16.

[0052] Thereafter, before the toner of the interrupted image adheres to the secondary transfer roller 20, the secondary transfer roller 20 is separated from the intermediate transfer belt 16 before passing through the secondary transfer roller of the interrupted image. Also, before the interrupted image on the intermediate transfer belt 16 is cleaned by the cleaning blade of the belt cleaning device 21, the paper P is conveyed (C-3). Then, after passing through the secondary transfer roller of the interrupted image and before passing through the secondary transfer roller of the re-formed image, the secondary transfer roller 20 is brought into contact with the intermediate transfer belt 16, and the re-formed image is transferred to the paper P by the secondary transfer roller 20 (C-4).

[0053] In this case, retry control (resending before pre-image cleaning) can reduce downtime more than retry control (resending after pre-image cleaning). Although retry control (resending before pre-image cleaning) has been known in the past, the image length (image interval) of the blank portion has not been noticed. According to the embodiment of FIG. 5(c), by shortening the image interval, further reduction of downtime is possible. Usually, during continuous printing, the interval between sheets cannot be easily shortened due to restrictions such as the amount of heat for fixing toner to the paper P. Since the retry control in this embodiment is an operation in a state where the printer main body is printable, it is possible to shorten the image length (image interval) of the blank portion.

[0054] FIG. 6 is a flowchart showing the operations of retry control (resending before pre-image cleaning) (a) and retry control (resending after pre-image cleaning) (b). Specifically, in the retry control (resending after pre-image cleaning) of FIG. 6(b), when a retry control notification is made in the printer 100, the toner image on the photoreceptor is switched to blank paper (S1), the secondary transfer roller 20 is separated from the intermediate transfer belt 16 (S2), and the paper feeding operation and image formation are interrupted until the toner image on the intermediate transfer belt 16 passes through the belt cleaning device 21 (S3). After passing, the toner image on the photoreceptor is switched to a printed image (S4), and the paper feeding is restarted (S5). Then, the secondary transfer roller 20 is brought into contact with the intermediate transfer belt 16 (S6), the secondary transfer bias is switched to the image portion bias (S7), the toner image on the intermediate transfer belt 16 and the paper P reach the secondary transfer roller 20, and the toner image is transferred to the paper P, and the retry control ends.

[0055] On the other hand, in the retry control (resending before pre-image cleaning) of FIG. 6(a), since image formation is restarted before the toner image on the intermediate transfer belt 16 passes through the belt cleaning device 21 after S2 (S4), the downtime is shorter because S3 is unnecessary.

[0056] Next, examples and comparative examples of the present invention will be described. The RICOH IM C3000 was used as the printer 100. A3-sized thick paper was set in the second tray of the printer main body and evaluated. The A5-sized paper was set so that the end face perpendicular to the conveyance direction was long. After the paper feed started, if the paper did not reach the registration sensor between the main body second tray and the registration roller even after a predetermined time had elapsed, retry control was started. In the embodiment, the inter-image distance was set to a value calculated by the product of the separation time of the secondary transfer roller (including the secondary transfer bias switching time) and the process line speed. In the comparative example, the inter-image distance was set to the paper distance during normal printing. When comparing the time from job submission to the printer 100 to the completion of the discharge of the reprinted image, about 0.1 seconds was shortened in the embodiment compared to the comparative example.

Explanation of Signs

[0057] 2 Image carrier 16 Intermediate transfer belt (intermediate transfer body) 19 Primary transfer roller (primary transfer unit) 20 Secondary transfer roller (secondary transfer unit) 21 Belt cleaning device (cleaning unit) 30 Paper feed tray (storage unit) 100 Image forming apparatus 107 Retry control unit

Prior Art Documents

Patent Documents

[0058]

Patent Document 1

Claims

1. An image forming unit that forms an image on an image carrier; A primary transfer unit that transfers the image formed on the image carrier to an intermediate transfer body; A secondary transfer unit that transfers the image transferred to the intermediate transfer body to a recording medium; A cleaning unit that cleans the intermediate transfer body; A feeding unit that feeds the recording medium from a storage unit that stores the recording medium to the secondary transfer unit; A determination unit that determines whether a feeding time for feeding the recording medium to the secondary transfer unit exceeds a predetermined time; In an image forming apparatus having a retry control unit that controls a formation timing of the image on the image carrier and a feeding timing of the recording medium in the feeding unit so that, when the feeding time exceeds the predetermined time, a position of the image formed on the image carrier and the recording medium coincides at the secondary transfer unit, when the feeding time exceeds the predetermined time, image formation on the image carrier is interrupted, and then image formation on the image carrier is resumed, and the image re-formed on the intermediate transfer body is conveyed to the secondary transfer unit together with the interrupted image, before the interrupted image passes through the secondary transfer unit, the secondary transfer unit is separated from the intermediate transfer body, and after the interrupted image passes through the secondary transfer unit and the cleaning unit and before the re-formed image passes through the secondary transfer unit, the secondary transfer unit is brought into contact with the intermediate transfer body, a time from when the secondary transfer unit is separated from the intermediate transfer body until it comes into contact with the intermediate transfer body is a separation time, an image interval distance of a blank paper portion between the interrupted image removed in the cleaning unit and the image re-formed on the intermediate transfer body is a product of the separation time of the secondary transfer unit from the intermediate transfer body and a process line speed, An image forming apparatus characterized by this.

2. The image forming apparatus according to claim 1, wherein when the feeding time exceeds the predetermined time, image formation on the image carrier is interrupted, and image formation on the image carrier is resumed before the image on the intermediate transfer body is removed in the cleaning unit.

Images