Image forming apparatus

Abstract

To provide an image forming apparatus that can detect toner images secondarily transferred to a conveying belt from all of image forming units included in the apparatus, with the same speed condition as that during conveyance of a recording medium.SOLUTION: An image forming apparatus including a plurality of image forming units comprises a first detection section that detects toner images secondarily transferred to a conveying belt, with a recording medium being conveyed by the conveying belt.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present disclosure relates to an image forming apparatus. [Background technology]

[0002] Patent document 1 describes an image forming device that forms a correction registration image on a conveying belt while a sheet of paper is placed on the conveying belt, thereby obtaining a correction registration image created on the conveying belt in the same state as when an image is actually formed on the paper.

[0003] Patent document 2 describes an image forming device that uses a beltless direct transfer method to transfer a toner pattern onto an image adjustment sheet stored in the device, thereby enabling image adjustment without wasting paper owned by the user. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-292789 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-191064 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present disclosure is to provide an image forming apparatus that can detect toner images secondarily transferred onto a conveying belt from all image forming units included in the apparatus under the same speed conditions as when conveying a recording medium. [Means for solving the problem]

[0006] The image forming apparatus of the first embodiment comprises a plurality of image forming units, each having a plurality of image forming sections and an intermediate transfer body onto which toner images formed in the plurality of image forming sections are primarily transferred; a conveying belt capable of conveying a recording medium onto which the toner image on the intermediate transfer body of each of the plurality of image forming units is secondarily transferred and onto which the toner image on the intermediate transfer body of each of the plurality of image forming units can be secondarily transferred; a first detection section that detects a toner image downstream of the most downstream secondary transfer position; a recording medium supply section that supplies a recording medium to the conveying belt; and a processor, wherein the processor detects the toner image secondarily transferred onto the conveying belt with the first detection section while the recording medium is being conveyed by the conveying belt.

[0007] The image forming apparatus of the second embodiment is the image forming apparatus of the first embodiment, and further includes a second detection unit provided in at least one of the image forming units, which detects a toner image between the most downstream primary transfer position and the secondary transfer position on the intermediate transfer body.

[0008] In a third embodiment of the image forming apparatus, in the image forming apparatus of the second embodiment, the processor obtains a positional deviation correction value using both the detection results of the first detection unit and the second detection unit, and uses the obtained positional deviation correction value to adjust the positional deviation of the toner image formed on the recording medium to which the toner image of the intermediate transfer body of each of the multiple image forming units is secondarily transferred, and when the conditions requiring the positional deviation correction value to be updated are met, the processor newly detects the toner image in the first detection unit and the second detection unit.

[0009] In the image forming apparatus of a fourth aspect, in the image forming apparatus of the second aspect, the first detection unit and the second detection unit detect the toner image at the same position in a direction perpendicular to the conveyance direction of the conveyor belt.

[0010] An image forming apparatus of a fifth aspect is the image forming apparatus of the first aspect, wherein the first detection unit is disposed at a position where the toner image is detected at a position where the conveyance belt is flat.

[0011] The image forming apparatus of a sixth aspect is the image forming apparatus of the fifth aspect, further comprising a roll that contacts the belt surface of the transport belt at a position facing the first detection unit across the transport belt. [Effects of the Invention]

[0012] According to the image forming apparatus of the first aspect, it is possible to detect the toner images secondarily transferred onto the conveyance belt from all image forming units included in the apparatus under the same speed conditions as when conveying the recording medium.

[0013] According to the image forming apparatus of the second aspect, it is possible to detect the toner image that has been primarily transferred in the image forming unit.

[0014] According to the image forming apparatus of the third aspect, the first detection unit and the second detection unit can newly detect the toner image at the timing when the positional deviation correction value needs to be updated.

[0015] According to the image forming apparatus of the fourth aspect, the first detection unit and the second detection unit can detect the same position of the toner image.

[0016] According to the fifth embodiment of the image forming apparatus, the influence of vibrations on the belt surface can be reduced when detecting a toner image that has been secondarily transferred onto the conveying belt, compared to when detecting a toner image at a position where the conveying belt is curved.

[0017] According to the image forming apparatus of the sixth aspect, it is possible to detect the toner image secondarily transferred onto the conveyor belt without being affected by vibration of the belt surface of the conveyor belt. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a diagram illustrating a configuration of an image forming apparatus according to a first embodiment. [Figure 2] FIG. 2 is a diagram illustrating a configuration of an image forming unit in the image forming apparatus. [Figure 3] 5A and 5B are diagrams illustrating an example of a toner image for adjusting misregistration in the image forming apparatus. [Figure 4] FIG. 2 is a diagram illustrating a configuration of an optical sensor in the image forming apparatus. [Figure 5] FIG. 2 is a diagram illustrating a configuration of a control unit in the image forming apparatus. [Figure 6] 5A to 5C are diagrams for explaining a method of adjusting misregistration in the image forming apparatus. [Figure 7] 10 is a flowchart illustrating a process flow when adjusting misregistration in the image forming apparatus. [Figure 8] 10 is a graph showing the relationship between the amount of misregistration in the intermediate transfer belt of the image forming unit and the amount of misregistration in other parts. [Figure 9] 10A and 10B are diagrams illustrating a state of paper transport when detected by an optical sensor in the image forming apparatus. [Figure 10] 10 is a graph illustrating the difference between detection by an optical sensor on a flat portion and detection by an optical sensor on a curved portion of the conveyor belt. [Figure 11] 10A and 10B are diagrams illustrating an example of a toner image for adjusting misregistration in an image forming apparatus according to a second embodiment. [Figure 12] 10 is a flowchart illustrating a process flow when adjusting misregistration in the image forming apparatus. [Figure 13] FIG. 10 is a diagram illustrating a configuration of an image forming apparatus according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] [First embodiment] Next, a first embodiment of the present disclosure will be described in detail with reference to the drawings.

[0020] <Image forming device> Fig. 1 is a diagram showing the configuration of an image forming apparatus 10 according to a first embodiment of the present disclosure. As shown in Fig. 1, the image forming apparatus 10 includes a storage section 12 for storing paper sheets PP, a transport section 11 for transporting the paper sheets PP along a transport path 19, and image forming units 30 and 50 for forming toner images to be transferred onto the paper sheets PP. The paper sheets PP are an example of a recording medium according to the technology of the present disclosure.

[0021] The storage section 12 can be pulled out from the image forming apparatus main body 10A, which is the main body of the image forming apparatus 10, and stores paper PP.

[0022] The conveying section 11 includes, in order from the upstream side in the conveying direction, a delivery roll 13, a conveying roll 14, a pair of registration rolls 15, a conveying belt device 20, a fixing device 18, and a discharge roll 17.

[0023] The delivery roll 13 delivers the paper sheet PP stored in the storage section 12 to a transport path 19 that constitutes the transport section 11. The transport roll 14 transports the paper sheet PP along the transport path 19.

[0024] The pair of registration rolls 15 transports the sheet PP transported by the transport rolls 14 to a secondary transfer position TJ2 on the downstream side, which will be described later. The pair of registration rolls 15 sandwiches the sheet PP between a registration roll 15A and a pinch roll 15B, and transports the sheet PP downstream in the transport direction.

[0025] The conveyor belt device 20 transfers the toner images formed by the image forming units 30 and 50 onto the paper PP, while conveying the paper PP downstream in the conveying direction along the conveying path 19. Details of the conveyor belt device 20 will be described later.

[0026] The fixing device 18 has a pair of fixing rolls 16, and heats and presses the paper PP onto which the toner image has been transferred as it passes between the pair of fixing rolls 16, thereby fixing the toner image to the paper PP.

[0027] The discharge rollers 17 discharge the paper PP onto which the toner image has been fixed by the fixing device 18 to the discharge section 9.

[0028] The image forming unit 30 and the image forming unit 50 are arranged side by side in the vertical direction. In this embodiment, the image forming unit 50 is arranged above the image forming unit 30. From another perspective, the image forming unit 50 is arranged downstream of the image forming unit 30 in the paper transport direction.

[0029] The image forming unit 30 forms toner images of special colors other than the basic colors of yellow (Y), magenta (M), cyan (C), and black (K), for example. The image forming unit 30 includes four image forming sections 32 and an endless intermediate transfer belt 40. The intermediate transfer belt 40 has the toner images formed by the four image forming sections 32 transferred thereto and is mounted so as to be rotatable counterclockwise when viewed from the front in FIG. 1.

[0030] The image forming units 32 include, for example, image forming unit 32P that forms a toner image of the special color pink (P), image forming unit 32S that forms a toner image of silver (S), image forming unit 32G that forms a toner image of gold (G), and image forming unit 32Gr that forms a toner image of the special color green (Gr). These four image forming units 32 are arranged in the following order from the upstream side in the rotation direction of the intermediate transfer belt 40 (the side closer to the support roll 44 described later): image forming unit 32P, image forming unit 32S, image forming unit 32G, and image forming unit 32Gr.

[0031] In the following description, the upstream side in the rotation direction of the intermediate transfer belt 40 is referred to as the "upstream side in the rotation direction," and the downstream side in the rotation direction is referred to as the "downstream side in the rotation direction." That is, in the image forming unit 32, the image forming unit 32Gr is disposed on the most downstream side in the rotation direction. In addition, in the image forming unit 32, the image forming unit 32Gr is disposed at a position closest to the secondary transfer position TJ2.

[0032] In addition, when there is no need to distinguish between P, S, G, and Gr, they will be omitted.

[0033] 2, the image forming unit 32 includes a photoconductor 33, a charging member 34 that charges the surface of the photoconductor 33, an exposure device 35 that irradiates the charged photoconductor 33 with light, and a developing device 36 that develops the electrostatic latent image formed by the exposure light and visualizes it as a toner image. The developing device 36 has a developing roll 39, and a developing bias is applied to it.

[0034] Furthermore, primary transfer rolls 37P, 37S, 37G, and 37Gr are disposed opposite the photoconductors 33 with the intermediate transfer belt 40 interposed therebetween, and transfer the toner images formed by the image forming unit 32 onto the intermediate transfer belt 40. The intermediate transfer belt 40 is wound around a support roll 44 that supports the intermediate transfer belt 40 and a backup roll 42 that is disposed in a secondary transfer unit 74 on the upstream side, which will be described later. The photoconductors 33, the primary transfer rolls 37, and the intermediate transfer belt 40 form a primary transfer unit 70. The positions between the photoconductors 33P, 33S, 33G, and 33Gr and the intermediate transfer belt 40 are designated as primary transfer positions TP1, TS1, TG1, and TGr1, respectively.

[0035] The image forming unit 50 has the same configuration as the image forming unit 30 except for the colors of the images it forms. The image forming unit 50 forms toner images of the basic colors, for example, yellow, magenta, cyan, and black.

[0036] The image forming unit 50 includes four image forming sections 52 and an intermediate transfer belt 60. The intermediate transfer belt 60 has toner images formed by the four image forming sections 52 transferred thereto and is mounted so as to be rotatable counterclockwise when viewed from the front in FIG.

[0037] 2, the image forming section 52 has the same configuration as the image forming section 32 of the image forming unit 30 except for the color of the image formed. The intermediate transfer belt 60 and the primary transfer roll 57, which will be described later, also have the same configuration as the intermediate transfer belt 40 and the primary transfer roll 37 of the image forming unit 30. The other components of the image forming unit 50 are also the same as those of the image forming unit 30.

[0038] The image forming unit 52 includes an image forming unit 52Y that forms a yellow toner image, an image forming unit 52M that forms a magenta toner image, an image forming unit 52C that forms a cyan toner image, and an image forming unit 52K that forms a black toner image. The four image forming units 52 are arranged in the following order from the upstream side in the rotation direction (the side closest to the support roll 64, which will be described later): image forming unit 52Y, image forming unit 52M, image forming unit 52C, and image forming unit 52K. That is, of the image forming units 52, the image forming unit 52K is arranged furthest downstream in the rotation direction. Furthermore, of the image forming units 52, the image forming unit 52K is arranged in a position closest to the secondary transfer position TK2.

[0039] It should be noted that when there is no need to distinguish between Y, M, C, and K, they will be omitted.

[0040] The image forming section 52 includes a photoreceptor 53, a charging member 54, an exposure device 55, and a developing device 56. The developing device 56 has a developing roll 59, and a developing bias is applied to it.

[0041] Additionally, primary transfer rolls 57Y, 57M, 57C, and 57K are disposed at positions facing each photoconductor 53 with the intermediate transfer belt 60 interposed therebetween. The intermediate transfer belt 60 is wound around a support roll 64 and a backup roll 62 disposed in a downstream secondary transfer unit 76, which will be described later. The photoconductors 53, primary transfer rolls 57, and intermediate transfer belt 60 constitute a primary transfer unit 72. The positions between the photoconductors 53Y, 53M, 53C, and 53K and the intermediate transfer belt 60 are designated as primary transfer positions TY1, TM1, TC1, and TK1, respectively.

[0042] Next, a detailed description will be given of the conveyor belt device 20. As shown in Fig. 1, the conveyor belt device 20 includes an endless conveyor belt 21, support rolls 22 and 23 that support the conveyor belt 21, and secondary transfer rolls 24 and 25 that are arranged in positions facing the backup rolls 42 and 62 with the intermediate transfer belts 40 and 60 interposed therebetween.

[0043] The secondary transfer roll 24 sandwiches the paper PP and the conveyor belt 21 between itself and the backup roll 42, and transfers the toner image formed on the intermediate transfer belt 40 of the image forming unit 30 onto the paper PP. Similarly, the secondary transfer roll 25 sandwiches the paper PP and the conveyor belt 21 between itself and the backup roll 62, and transfers the toner image formed on the intermediate transfer belt 60 of the image forming unit 50 onto the paper PP.

[0044] The backup roll 42, the secondary transfer roll 24, and the intermediate transfer belt 40 constitute a secondary transfer unit 74. The backup roll 62, the secondary transfer roll 25, and the intermediate transfer belt 60 constitute a secondary transfer unit 76.

[0045] A transfer bias is applied to each of the secondary transfer rolls 24 and 25.

[0046] Further, the space between the intermediate transfer belt 40 of the image forming unit 30 and the conveyor belt 21 is defined as a secondary transfer position TJ2, and the space between the intermediate transfer belt 60 of the image forming unit 50 and the conveyor belt 21 is defined as a secondary transfer position TK2. The secondary transfer position TK2 is the most downstream secondary transfer position.

[0047] The conveyor belt device 20 also includes a belt cleaning device 78 that cleans the conveyor belt 21. The belt cleaning device 78 performs cleaning downstream of the most downstream secondary transfer position TK2 in the paper conveying direction and downstream of an optical sensor 150, which will be described later. The position on the conveyor belt 21 that is cleaned by the belt cleaning device 78 is referred to as a cleaning position CL.

[0048] In this embodiment, the toner image BC used for misregistration adjustment has the pattern shown in FIG.

[0049] The toner image BC includes eight toner images of yellow, magenta, cyan, black, special pink, silver, gold, and special green. The toner images of each color have the same shape and include horizontal lines and diagonal lines that extend in the main scanning direction (the up-and-down direction in the figure) of the image forming units 30 and 50.

[0050] The toner images BC are arranged in three rows, each extending in the sub-scanning direction (left-right direction in the drawing) of the image forming units 30 and 50. The patterns in each row are the same, with black toner images BCK and toner images of colors other than black arranged alternately. The toner images are also arranged at equal intervals.

[0051] In this way, by using three rows of toner images BC extending in the sub-scanning direction, it is possible to independently adjust positional deviations at three locations in the main scanning direction (for example, both ends and the center).

[0052] The toner image BC for adjusting misalignment is formed as follows: First, as shown in Fig. 3(A), of the toner image BC, the pink toner image BCP, the silver toner image BCS, the gold toner image BCG, and the green toner image BCGr are primarily transferred onto the intermediate transfer belt 40.

[0053] Also, as shown in Figure 3(B), of the toner image BC, the yellow toner image BCY, the magenta toner image BCM, the cyan toner image BCC, and the black toner image BCK are primarily transferred onto the intermediate transfer belt 60.

[0054] Finally, as shown in FIG. 3C, the toner image BC that has been primarily transferred onto the intermediate transfer belts 40 and 60 is secondarily transferred onto the conveyor belt 21, becoming a toner image BC for adjusting positional deviation.

[0055] As shown in FIG. 1, an optical sensor 150 as an example of a first detection unit that detects a toner image BC secondarily transferred onto the conveyor belt 21 is provided at a position facing the support roll 23 across the conveyor belt 21.

[0056] The optical sensor 150 is disposed downstream of the most downstream secondary transfer position TK2. From another perspective, the optical sensor 150 is disposed at a position where it can detect all of the toner images BC formed by all of the image forming units 32Y, 32M, 32C, 32W, 52T, 52S, 52G, and 52K.

[0057] The optical sensor 150 detects the toner image BC at a flat portion 21Q between the secondary transfer position TK2 and the upper support roll 23 around which the conveyor belt 21 is wound. In this embodiment, the optical sensor 150 detects the toner image BC at a position facing the support roll 23 in the flat portion 21Q.

[0058] The position of the optical sensor 150 is not limited to the above position, and in this embodiment, it is sufficient that it is placed at a position where it can detect the toner image BC upstream in the rotation direction of the most downstream secondary transfer position TK2 and upstream in the rotation direction of the cleaning position CL.

[0059] Further, optical sensors 154 and 156 as an example of a second detection unit that detects the toner image BC primarily transferred onto the intermediate transfer belts 40 and 60 are provided in the image forming units 30 and 50, respectively.

[0060] An optical sensor 154 provided in the image forming unit 30 detects the toner image BC near the backup roll on the flat portion 40Q of the intermediate transfer belt 40 between the most downstream primary transfer position TW1 and the backup roll .

[0061] An optical sensor 156 provided in the image forming unit 50 detects the toner image BC at the most downstream primary transfer position TK1, near the backup roll 62 on the flat portion 60Q of the intermediate transfer belt 60 between the primary transfer position TK1 and the backup roll 62.

[0062] In this embodiment, optical sensor 150, optical sensor 154, and optical sensor 156 have the same structure. Furthermore, optical sensor 150, optical sensor 154, and optical sensor 156 detect toner image BC at the same position in the axial direction of each roll (Z direction in FIG. 1).

[0063] The axial direction of each roll corresponds to the main scanning direction in the image forming units 30 and 50. The conveying direction of the conveyor belt 21 corresponds to the sub-scanning direction in the image forming units 30 and 50.

[0064] As shown in FIG. 4, the optical sensors 150, 154, and 156 of this embodiment have three detection sections 150A, 154A, and 156A, detection sections 150B, 154B, and 156B, and detection sections 150C, 154C, and 156C arranged at intervals along the axial direction of each roll.

[0065] The detecting sections 150A, 154A, 156A, the detecting sections 150B, 154B, 156B, and the detecting sections 150C, 154C, 156C are each disposed at a position corresponding to each row of the toner image BC for adjusting misregistration shown in FIG.

[0066] <Control unit> Next, the control unit 80 that controls the operation of the image forming apparatus 10 will be described with reference to FIG.

[0067] As shown in FIG. 5, the control unit 80 is electrically connected to the image forming unit 30, the image forming unit 50, the communication unit 90, the nonvolatile memory 92, the supply device 120, the power supply device 159, the optical sensors 150, 154, 156, etc.

[0068] The control unit 80 includes a CPU (Central Processing Unit) 81, a ROM (Read Only Memory) 82, a RAM (Random Access Memory) 83, and an input / output interface (I / O) 84, which are connected to each other via a bus.

[0069] Here, the ROM 82 stores an image formation control program (not shown) that is executed by the CPU 81. The CPU 81 reads the image formation control program (not shown) from the ROM 82 and loads it into the RAM 83, thereby executing a print process according to the image formation control program (not shown).

[0070] Also connected to the I / O 84 are the image forming unit 30, the image forming unit 50, a communication unit 90, and a non-volatile memory 92. The communication unit 90 is an interface for mutual data communication between a terminal device such as a personal computer (not shown) and the image forming apparatus 10. The non-volatile memory 92 stores information necessary for the image forming apparatus 10 to perform an image forming operation.

[0071] The control unit 80 performs various controls to form a toner image on the intermediate transfer belt 40 by the image forming unit 32 of each color in the image forming unit 30. Similarly, the control unit 80 performs various controls to form a toner image on the intermediate transfer belt 60 by the image forming unit 52 of each color in the image forming unit 50.

[0072] The control unit 80 also controls the developing biases applied to the developing rolls 39 and 59 of the developing devices 36 and 56. Furthermore, the control unit 80 controls the transfer biases applied to the secondary transfer rolls 24 and 25, respectively.

[0073] The control unit 80 also controls the timing, time, and amount of toner supplied from the toner cartridges of each color to the developing devices 36 and 56 .

[0074] Furthermore, the detection value of the toner image BC detected by the optical sensor 150 is input to the control unit 80. Then, based on these detection values, the timing of forming the toner image on the intermediate transfer belts 40 and 60 of the image forming units 30 and 50, specifically, the timing of exposure of the exposure devices 35 and 55, the developing bias applied to the developing rolls 39 and 59, the transfer bias applied to the secondary transfer rolls 24 and 25, etc. are controlled.

[0075] The details of various controls based on the detection value of the toner image BC detected by the optical sensor 150 will be described later.

[0076] <Image forming process> Next, an outline of the image forming process in the image forming apparatus 10 will be described.

[0077] First, the control unit 80 controls each image forming unit 32 so that a toner image is formed on the intermediate transfer belt 40 of the image forming unit 30. Similarly, the control unit 80 controls each image forming unit 52 so that a toner image is formed on the intermediate transfer belt 60 of the image forming unit 50.

[0078] Specifically, the control unit 80 applies a voltage to the charging members 34, 54, which charge the surfaces of the photoconductors 33, 53 to a predetermined potential. Next, the control unit 80 causes the exposure devices 35, 55 to irradiate light onto the surfaces of the photoconductors 33, 53 charged by the charging members 34, 54 based on image data acquired via the communication unit 90, thereby forming an electrostatic latent image. As a result, an electrostatic latent image corresponding to the image data is formed on the surfaces of the photoconductors 33, 53.

[0079] Next, the control unit 80 controls the developing devices 36, 56 to develop the electrostatic latent images formed by the exposure devices 35, 55, and visualize them as toner images. Furthermore, the control unit 80 controls the primary transfer rolls 37, 57 to transfer the toner images formed on the surfaces of the photoreceptors 33, 53 of each color onto the intermediate transfer belts 40, 60 in a superimposed manner.

[0080] In this way, in the image forming unit 30, a toner image in which, for example, special color pink, silver, gold, and special color green toners are superimposed is formed on the intermediate transfer belt 40. Similarly, in the image forming unit 50, a toner image in which, for example, yellow, magenta, cyan, and black toners are superimposed is formed on the intermediate transfer belt 60.

[0081] When the toner image is transferred onto the conveyor belt 21, the transfer area of ​​the conveyor belt 21 is sent to the secondary transfer position TJ2 under the control of the control unit 80. At this secondary transfer position TJ2, the conveyor belt 21 is conveyed between the backup roll 42 and the secondary transfer roll 24, so that the toner image on the outer circumferential surface of the intermediate transfer belt 40 is transferred onto the conveyor belt 21. Then, the transfer area of ​​the conveyor belt 21 onto which the toner image has been transferred is conveyed downstream in the conveyance direction to reach the secondary transfer position TK2 on the downstream side in the conveyance direction.

[0082] At this time, the control unit 80 adjusts the timing at which image formation begins so that the toner image formed on the intermediate transfer belt 60 of the image forming unit 50 is transferred and superimposed on the toner image on the transfer area of ​​the conveying belt 21 conveyed from the upstream side in the conveying direction.

[0083] Furthermore, when a toner image is transferred to paper PP, paper PP is sent from storage unit 12 to transport path 19 by delivery roll 13, and the transport timing is adjusted by registration roll pair 15 under the control of control unit 80, and then paper PP is sent to secondary transfer position TJ2. At secondary transfer position TJ2, paper PP is transported between backup roll 42 and secondary transfer roll 24, so that the toner image on the outer peripheral surface of intermediate transfer belt 40 is transferred to paper PP. Then, paper PP with the toner image transferred thereto is transported downstream in the transport direction to secondary transfer position TK2, which is also downstream in the transport direction.

[0084] At this time, the control unit 80 adjusts the timing for starting image formation so that the toner image formed on the intermediate transfer belt 60 of the image forming unit 50 is transferred and superimposed on the toner image on the paper PP transported from the upstream side in the transport direction.

[0085] The paper PP onto which the toner images of each color formed by the image forming unit 30 and the image forming unit 50 are superimposed and transferred is fixed by the pair of fixing rolls 16 of the fixing device 18, and then discharged by the discharge roll 17 to the discharge section 9 provided at the top of the image forming device main body 10A.

[0086] <Adjusting misalignment> Next, we will explain the so-called color registration control, which is the adjustment of the positional deviation in the sub-scanning direction of the images obtained by superimposing the toner images of the special colors pink, silver, gold, green, yellow, magenta, cyan, and black formed by the image forming sections 32 of the image forming unit 30 and the image forming sections 52 of the image forming unit 50. Note that the color registration control in this embodiment is performed by timing the exposure of the exposure devices 35 and 55.

[0087] Specifically, the toner image BC for adjusting the positional deviation transferred onto the conveyor belt 21 is detected by the optical sensor 150, and the exposure timing of the exposure devices 35P, 35S, 35G, 35Gr, 55Y, 55M, 55C, and 55K is adjusted so that the toner image BC is positioned at a predetermined position.

[0088] Any method may be used to adjust the positional deviation, but in this embodiment, the positional deviation is adjusted as follows.

[0089] In this embodiment, the positional deviation is adjusted based on the black toner image BCK in the toner image BC for positional deviation adjustment, as shown in Fig. 6. Specifically, the positional deviation of the toner images of the colors sandwiched between the two black toner images BCK (hereinafter referred to as toner images BCn of the other colors) is adjusted as follows.

[0090] Main scanning misalignment: "The center position of the centers of gravity of the diagonal lines of the two black toner images BCK" - "The center position of the centers of gravity of the diagonal lines of the other color toner images BCn" - "Misalignment in the sub-scanning direction"

[0091] Misalignment in the cross-scan direction: "The center position of the horizontal lines of the two black toner images BCK" - "The center position of the horizontal lines of the other color toner images BCn"

[0092] The above adjustment is performed for the special colors pink, silver, gold, green, yellow, magenta, and cyan, excluding black.

[0093] <effect> Next, the operation of the image forming apparatus 10 of this embodiment will be described.

[0094] The flow of processing when adjusting misalignment in the image forming apparatus 10 of this embodiment is as shown in the flowchart of FIG.

[0095] First, in step S01, the control unit 80 determines whether or not to perform positional deviation adjustment. If it is determined in step S01 that positional deviation adjustment is not to be performed, the control unit 80 ends the process.

[0096] If it is determined in step S01 that misregistration adjustment is to be performed, the control unit 80 generates a toner image BC for misregistration adjustment using all colors and transfers it onto the conveyor belt 21 in step S02.

[0097] Next, in step S03, the control unit 80 uses the optical sensor 150 to obtain the amount of misregistration between the colors from the toner image BC transferred onto the conveyor belt 21.

[0098] Finally, in step S04, the control unit 80 calculates correction values ​​from the amounts of misregistration between colors, adjusts the exposure timings of the exposure devices 35P, 35S, 35G, 35Gr, 55Y, 55M, 55C, and 55K, and ends the process.

[0099] The relationship between the amount of misalignment in the intermediate transfer belts 40 and 60 of the image forming units 30 and 50 and the amount of misalignment in other parts is shown in the graph in Fig. 8. In the graph in Fig. 8, the horizontal axis represents the amount of misalignment (μm) in the intermediate transfer belt, and the vertical axis represents the amount of misalignment (μm) in other parts.

[0100] As shown in the graph of FIG. 8, when another intermediate transfer belt is subjected to approximately the same load conditions, the amount of misregistration between the reference color and other colors on the intermediate transfer belt is approximately the same.

[0101] Furthermore, when the speed of the conveyor belt 21 is slower than that of the intermediate transfer belts 40 and 60, the amount of positional deviation becomes smaller.

[0102] In the above example, when a positional deviation of about 80 μm is detected on the conveyor belt 21, the correction amount during primary transfer onto the intermediate transfer belts 40 and 60 must be about 100 μm.

[0103] Furthermore, when the conveyor belt 21 conveys the paper PP, the degree of change in the amount of misalignment varies depending on the paper conditions. This is because when the conveyor belt 21 conveys the paper PP, the speed of the conveyor belt 21 changes due to the influence of the shape and / or weight of the paper PP, etc.

[0104] In other words, when the conveyor belt 21 is not transporting the paper PP, the detection value obtained by the optical sensor 150 detecting the toner image BC transferred to the conveyor belt 21 cannot accurately adjust the positional deviation when the toner image is transferred to the paper PP.

[0105] To solve this problem, in the image forming apparatus 10 of this embodiment, as shown in FIG. 9, while the paper PP is being transported by the transport belt 21, the toner image BC that has been secondarily transferred onto the transport belt 21 is detected by the optical sensor 150.

[0106] Specifically, the secondary transfer of the toner image BC from the intermediate transfer belt 40 of the lower image forming unit 30 to the conveying belt 21 is completed, and the paper PP is supplied to the conveying belt 21 before the toner image BC is detected by the optical sensor 150.

[0107] As a result, when the optical sensor 150 detects the toner image BC, the speed of the conveyor belt 21 becomes the same as the speed of the conveyor belt 21 when the toner image is transferred onto the paper PP.

[0108] Therefore, by using the detection value obtained by the optical sensor 150 detecting the toner image BC transferred onto the conveyor belt 21 under these conditions, it is possible to accurately adjust the positional deviation when the toner image is transferred onto the paper PP.

[0109] In the image forming apparatus 10 of this embodiment, the optical sensor 150 is configured to detect the toner image BC on the flat portion 21Q of the conveyor belt 21.

[0110] Here, the difference between detection on the flat portion 21Q of the conveyor belt 21 and detection on the curved portion will be described.

[0111] When the optical sensor 150 detects the curved portion of the conveyor belt 21, the amount of light detected by the optical sensor 150 decreases, so the amount of light emitted by the optical sensor 150 needs to be increased compared to when detecting the flat portion 21Q.

[0112] 10, when detecting at the curved portion, the magnitude of the diffuse waveform relative to the magnitude of the specular reflection waveform, which is the detected waveform of the toner image BC, is larger than when detecting at the flat portion 21Q. Also, the time difference between the peak position of the specular reflection waveform and the peak position of the diffuse waveform is larger.

[0113] Therefore, by performing detection at the flat portion 21Q of the conveyor belt 21 as in this embodiment, the toner image BC can be detected more accurately than when detecting at the curved portion.

[0114] In the image forming apparatus 10 of this embodiment, the optical sensor 150 is configured to detect the toner image BC at a position facing the support roll 23.

[0115] In this case, the deflection of the conveyor belt 21 during detection is suppressed compared to when the toner image BC is detected in a portion of the conveyor belt 21 where there is nothing behind it as seen from the optical sensor 150. Therefore, the toner image BC can be detected more accurately compared to when the toner image BC is detected in a portion of the conveyor belt 21 where there is nothing behind it as seen from the optical sensor 150.

[0116] [Second embodiment] Next, a second embodiment of the present disclosure will be described. In the above first embodiment, a mode in which misalignment adjustment is performed based on a detection signal of a toner image BC by optical sensor 150 has been described. In contrast, in the second embodiment, a mode in which misalignment adjustment is performed based on a detection signal of a toner image BC by optical sensors 150, 154, and 156 will be described. The configuration of image forming apparatus 10 of the second embodiment is the same as that of image forming apparatus 10 of the first embodiment, and therefore description thereof will be omitted.

[0117] In this embodiment, the toner image BC used for misregistration adjustment has the pattern shown in FIG.

[0118] The toner image BC includes eight toner images of yellow, magenta, cyan, black, special pink, silver, gold, and special green. The toner images of each color have the same shape and include horizontal lines and diagonal lines that extend in the main scanning direction (the up-and-down direction in the figure) of the image forming units 30 and 50.

[0119] The toner image BC has three rows of patterns arranged in the sub-scanning direction (left-right direction in the drawing) in the image forming units 30 and 50. The patterns in each row are the same.

[0120] The toner image BC for adjusting misalignment is formed as follows: First, as shown in Fig. 11(A), of the toner image BC, the pink toner image BCP, the silver toner image BCS, the gold toner image BCG, and the green toner image BCGr are primarily transferred onto the intermediate transfer belt 40.

[0121] In the toner image BC that is primarily transferred onto the intermediate transfer belt 40, the toner image BCGr of the particular green color and the toner images of colors other than the particular green color are alternately arranged.

[0122] Also, as shown in Figure 11(B), of the toner image BC, the yellow toner image BCY, the magenta toner image BCM, the cyan toner image BCC, and the black toner image BCK are primarily transferred onto the intermediate transfer belt 60.

[0123] In the toner image BC that is primarily transferred onto the intermediate transfer belt 60, black toner images BCK and toner images of colors other than black are alternately arranged.

[0124] Finally, as shown in FIG. 11C, the toner image BC that has been primarily transferred onto the intermediate transfer belts 40 and 60 is secondarily transferred onto the conveyor belt 21, becoming a toner image BC for adjusting positional deviation.

[0125] In the toner image BC that is secondarily transferred onto the conveyor belt 21, a green toner image BCGr is disposed between two black toner images BCK in the area surrounded by the dotted line in Fig. 11(C). In addition, in the toner image BC that is secondarily transferred onto the conveyor belt 21, the individual toner images are disposed at equal intervals.

[0126] Next, the operation of the image forming apparatus 10 of this embodiment will be described.

[0127] The flow of processing when adjusting misalignment in the image forming apparatus 10 of this embodiment is as shown in the flowchart of FIG.

[0128] First, in step S11, the control unit 80 determines whether or not to perform misalignment adjustment. If it is determined in step S11 that misalignment adjustment is not to be performed, the control unit 80 ends the process.

[0129] If it is determined in step S11 that misregistration adjustment is to be performed, the control unit 80 generates a toner image BC for misregistration adjustment using all colors and primarily transfers it onto the intermediate transfer belts 40 and 60 in step S12.

[0130] Next, in step S13, the control unit 80 obtains the amount of misregistration between colors for each of the image forming units 30 and 50 from the toner images transferred onto the intermediate transfer belts 40 and 60 using the optical sensors 154 and 156.

[0131] When obtaining the amount of misregistration between colors in the image forming unit 30, the amount of misregistration of toner images other than the green special color is obtained using the green special color toner image BCGr as a reference. When obtaining the amount of misregistration between colors in the image forming unit 50, the amount of misregistration of toner images other than the black color is obtained using the black toner image BCK as a reference.

[0132] Next, in step S14, the control unit 80 performs second transfer of the toner images transferred onto the intermediate transfer belts 40 and 60 onto the conveyor belt 21.

[0133] Next, in step S15, the control unit 80 uses the optical sensor 150 to obtain the amount of misalignment between the image forming units 30 and 50 from the toner image transferred onto the conveyor belt 21.

[0134] Here, when obtaining the amount of misalignment between the image forming units 30 and 50, the amount of misalignment of the special green toner image BCGr formed by the image forming unit 30 is obtained using the black toner image BCK formed by the image forming unit 50 as a reference in the area surrounded by the dotted line in Figure 11 (C).

[0135] Finally, in step S16, the control unit 80 calculates a correction value from the amount of misalignment between colors within the image forming units 30 and 50 and the amount of misalignment between the image forming units 30 and 50, adjusts the exposure timing of the exposure devices 35P, 35S, 35G, 35Gr, 55Y, 55M, 55C, and 55K, and terminates the process.

[0136] In this way, by using the optical sensors 154 and 156 provided in the image forming units 30 and 50 respectively, the amount of misregistration between colors can be adjusted for each of the image forming units 30 and 50 .

[0137] In addition, in the image forming apparatus 10 of this embodiment, the control unit 80 may be configured to detect a new toner image BC for adjusting the positional deviation using the optical sensors 150, 154, and 156 when the conditions for updating the positional deviation correction value are met.

[0138] Here, the following cases may be considered as "conditions that require updating of the positional deviation correction value," for example. The first condition is when the positional deviation correction value is in its initial state. The second condition is when either the image forming unit 30, 50 has been removed or replaced since the previous adjustment was performed. The third condition is when the conveyor belt device 20 has been removed or replaced since the previous adjustment was performed. Conditions other than those mentioned above may also be used.

[0139] The optical sensors 150, 154, and 156 are configured to detect the toner images at the same positions in a direction perpendicular to the conveying direction of the conveyor belt 21.

[0140] This allows for more accurate adjustment of the amount of misregistration between colors than when the optical sensors 150, 154, and 156 detect the toner images at different positions in a direction perpendicular to the conveyance direction of the conveyor belt 21.

[0141] [Variations] The image forming apparatus 10 has been described above as one embodiment of the information processing system of the present disclosure, but the technology of the present disclosure is not limited to the above embodiment and can be modified as appropriate.

[0142] For example, the number of image forming units provided in the image forming apparatus 10 is not limited to two, but may be three or more.

[0143] 13, the optical sensor 150 may be disposed at a position where the toner image BC is detected on the flat portion 21R of the conveyor belt 21 opposite the secondary transfer positions TJ2 and TK2 across the support rolls 22 and 23.

[0144] In the above embodiment, the term "processor" refers to a processor in a broad sense, and includes general-purpose processors (e.g., CPU: Central Processing Unit, etc.) and dedicated processors (e.g., GPU: Graphics Processing Unit, ASIC: Application Specific Integrated Circuit, FPGA: Field Programmable Gate Array, programmable logic device, etc.).

[0145] Furthermore, the operations of the processors in the above embodiments may not only be performed by a single processor, but may also be performed by multiple processors located at physically separate locations working together. Furthermore, the order of the operations of the processors is not limited to the order described in the above embodiments, and may be changed as appropriate.

[0146] [Note] The following additional notes are provided regarding the above-described embodiment.

[0147] (((1))) a plurality of image forming units each having a plurality of image forming sections and an intermediate transfer body onto which the toner images formed in the plurality of image forming sections are primarily transferred; a conveyor belt capable of conveying a recording medium onto which the toner image of the intermediate transfer body of each of the plurality of image forming units is secondarily transferred, and onto which the toner image of the intermediate transfer body of each of the plurality of image forming units is secondarily transferred; a first detection unit that detects a toner image downstream of a most downstream secondary transfer position; a recording medium supply unit that supplies a recording medium to the conveyor belt; a processor, The processor: In a state where the recording medium is conveyed by the conveyance belt, the toner image secondarily transferred onto the conveyance belt is detected by the first detection unit. Image forming device.

[0148] (((2))) a second detection unit that is provided in at least one of the image forming units and detects a toner image between a primary transfer position and a secondary transfer position on the most downstream side of the intermediate transfer body; The image forming apparatus according to (((1))).

[0149] (((3))) The processor: acquiring a positional deviation correction value using both the detection results of the first detection unit and the second detection unit, and adjusting a positional deviation of a toner image formed on a recording medium onto which the toner image of the intermediate transfer body of each of the plurality of image forming units is secondarily transferred using the acquired positional deviation correction value; When a condition requiring updating of the positional deviation correction value is satisfied, the first detection unit and the second detection unit newly detect the toner image. The image forming apparatus according to (((2))).

[0150] (((4))) The first detection unit and the second detection unit detect the toner image at the same position in a direction perpendicular to the conveying direction of the conveyor belt. The image forming apparatus according to (((2))) or (((3))).

[0151] (((5))) The first detection unit is disposed at a position where the conveyance belt is flat and detects a toner image. The image forming apparatus according to any one of (((1))) to (((4))).

[0152] (((6))) a roller that contacts the belt surface of the conveyor belt and is disposed at a position facing the first detection unit across the conveyor belt; The image forming apparatus according to (((5))).

[0153] The effects of the configuration described above will be described below.

[0154] According to the image forming apparatus (((1))), the toner images secondarily transferred onto the conveyance belt from all image forming units provided in the apparatus can be detected under the same speed conditions as when conveying the recording medium.

[0155] According to the image forming apparatus of (((2))), it is possible to detect the toner image that has been primarily transferred in the image forming unit.

[0156] According to the image forming apparatus of (((3))), the first and second detection units can newly detect the toner image at the timing when the positional deviation correction value needs to be updated.

[0157] According to the image forming apparatus of (((4))), the first detection unit and the second detection unit can detect the same position of the toner image.

[0158] According to the image forming device (((5))), the influence of vibration of the belt surface can be reduced when detecting a toner image that has been secondarily transferred to the conveying belt, compared to when detecting a toner image at a position where the conveying belt is curved.

[0159] According to the image forming apparatus (((6))), it is possible to detect the toner image secondarily transferred onto the conveyor belt without being affected by vibration of the belt surface of the conveyor belt. [Explanation of symbols]

[0160] 10 Image forming device 11 Conveyor 12 Storage section 13 Sending Roll 14 Transport roll 15 Resist Roll Pair 16 Fixing roll pair 17 Ejection roll 18 Fixing device 19 Transport Route 20 Conveyor belt device 21 Conveyor belt 24, 25 Secondary transfer roll 30 Image forming unit 32 Image forming unit 40 Intermediate transfer belt 42 Backup Roll 44 Support Roll 50 Image forming unit 52 Image forming unit 60 Intermediate transfer belt 62 Backup Roll 64 Support Roll 78 Belt cleaning device 80 Control Unit 81 CPU 82 ROM 83 RAM 84 Input / Output Interface 90 Communications Department 92 Non-volatile memory 120 Feeding device 150, 154, 156 Optical sensors 159 Power supply

Claims

1. a plurality of image forming units each having a plurality of image forming sections and an intermediate transfer body onto which the toner images formed in the plurality of image forming sections are primarily transferred; a conveyor belt capable of conveying a recording medium onto which the toner image of the intermediate transfer body of each of the plurality of image forming units is secondarily transferred, and onto which the toner image of the intermediate transfer body of each of the plurality of image forming units is secondarily transferred; a first detection unit that detects a toner image downstream of a most downstream secondary transfer position; a recording medium supply unit that supplies a recording medium to the conveyor belt; a processor, The processor: In a state where the recording medium is conveyed by the conveyance belt, the toner image secondarily transferred onto the conveyance belt is detected by the first detection unit. Image forming device.

2. a second detection unit that is provided in at least one of the image forming units and detects a toner image between a primary transfer position and a secondary transfer position on the most downstream side of the intermediate transfer body; The image forming apparatus according to claim 1 .

3. The processor: acquiring a positional deviation correction value using both the detection results of the first detection unit and the second detection unit, and adjusting a positional deviation of a toner image formed on a recording medium onto which the toner image of the intermediate transfer body of each of the plurality of image forming units is secondarily transferred using the acquired positional deviation correction value; When a condition requiring updating of the positional deviation correction value is satisfied, the first detection unit and the second detection unit newly detect the toner image. The image forming apparatus according to claim 2 .

4. The first detection unit and the second detection unit detect the toner image at the same position in a direction perpendicular to the conveying direction of the conveyor belt. The image forming apparatus according to claim 2 .

5. The first detection unit is disposed at a position where the conveyor belt is flat and detects a toner image. The image forming apparatus according to claim 1 .

6. a roller that contacts the belt surface of the conveyor belt and is disposed at a position facing the first detection unit across the conveyor belt; The image forming apparatus according to claim 5 .

Images