Image-forming device

Abstract

To prevent variation in a conveyance speed when a paper sheet passes a paper sheet position adjustment roll from being simultaneously transferred to secondary transfer positions in two places.SOLUTION: A secondary transfer section 74 performs secondary transfer of a toner image formed on an intermediate transfer belt 40 onto a paper sheet PP conveyed on a paper sheet conveyance path. A secondary transfer section 76 also performs secondary transfer of a toner image formed on an intermediate transfer belt 60 onto the paper sheet PP conveyed on the paper sheet conveyance path. A resist roll 15 is a paper sheet position adjustment roll for conveying the paper sheet PP fed from a paper sheet storage section 12 to a secondary transfer position TJ2 in which secondary transfer is performed by the secondary transfer section 74 at predetermined timing. The distance between the resist roll 15 and a secondary transfer position TK2 in which secondary transfer is performed by the secondary transfer section 76 is configured to be longer than the maximum paper length that is the length in the conveyance direction of a paper sheet having the largest paper sheet size from among paper sheets that may be used.SELECTED DRAWING: Figure 6

Description

[Technical Field]

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

[0002] Patent document 1 discloses a printing device in which multiple engine units are stacked vertically, and a common discharge and conveying means, a speed switching control means, a high-speed rotation holding control means, and a timing regulation means are provided, so that the amount of print data can be shared and printed by each engine unit, and printed paper discharged from each engine unit can be discharged at high speed to a common paper receiver by the machine's own conveying means or the common discharge and conveying means.

[0003] Patent document 2 discloses an image forming apparatus in which a plurality of image forming units are arranged in parallel, for example vertically, and toner images are transferred sequentially onto a transfer material at the transfer site of each image forming unit, in which each image forming unit is provided with a transporting and transferring means, and the distance on the transfer material transport path between the nip transporting means on the entrance and exit sides is set to be shorter than the transport direction length of a transfer material of standard use size, or the transfer material of the minimum use size is nipped across the transporting and transferring means of at least a plurality of image forming units, without being nipped by the nip transporting means on the entrance and exit sides simultaneously. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 8-211673 [Patent Document 2] Japanese Patent Application Publication No. 9-325560 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, in order to expand the color gamut of images formed by image forming devices, images have begun to be formed using not only toners of the basic colors CMYK, but also toners of special colors other than CMYK. Such image forming devices may be configured to form toner images on paper using two image forming units, each equipped with multiple image forming sections that form toner images. Each image forming unit performs a primary transfer of the toner images formed by the multiple image forming sections onto an intermediate transfer body, and the toner image on the intermediate transfer body is then secondary transferred onto paper transported along a paper transport path. In other words, when a toner image is formed on paper using two image forming units, secondary transfer occurs at two secondary transfer positions.

[0006] An object of the present disclosure is to provide an image forming apparatus that can prevent fluctuations in the transport speed when paper passes through paper position adjustment rolls from being transmitted to two secondary transfer positions simultaneously. [Means for solving the problem]

[0007] The image forming apparatus of the first aspect of the present disclosure includes a first image forming unit having a plurality of first image forming sections and a first intermediate transfer body onto which toner images formed by the plurality of first image forming sections are primarily transferred; a second image forming unit provided downstream of the first image forming unit in a paper transport direction, the second image forming unit having a plurality of second image forming units and a second intermediate transfer body onto which toner images formed by the plurality of second image forming units are primarily transferred; a first secondary transfer unit provided corresponding to the first image forming unit, which performs a second transfer of the toner image formed on the first intermediate transfer body onto a sheet of paper transported on a paper transport path; a second secondary transfer unit provided corresponding to the second image forming unit, which performs a second transfer of the toner image formed on the second intermediate transfer body onto a sheet of paper transported on a paper transport path; a paper position adjustment roll that transports the fed paper at a predetermined timing to a first secondary transfer position where secondary transfer is performed by the first secondary transfer unit, The distance between the paper position adjustment roll and the second secondary transfer position where secondary transfer is performed by the second secondary transfer unit is longer than the maximum paper length, which is the length in the transport direction of the largest paper size that may be used.

[0008] An image forming apparatus according to a second aspect of the present disclosure is the image forming apparatus according to the first aspect, further comprising a fixing unit that fixes the toner image on the paper sheet after secondary transfer by the second secondary transfer unit, to the paper sheet; The distance between a fixing position where the fixing unit fixes the toner image onto the paper and a first secondary transfer position where the first secondary transfer unit performs secondary transfer is longer than the maximum paper length.

[0009] An image forming apparatus of a third aspect of the present disclosure is the image forming apparatus of the second aspect, in which the fixing section fixes the toner image to the paper while reducing the transport speed of the paper transported along the paper transport path at the fixing position.

[0010] An image forming apparatus of a fourth aspect of the present disclosure is the image forming apparatus of the first aspect, wherein the distance between the paper position adjustment roll and the first secondary transfer position where secondary transfer is performed by the first secondary transfer unit is shorter than the minimum paper length, which is the length in the transport direction of the smallest paper size among the papers that may be used.

[0011] An image forming apparatus according to a fifth aspect of the present disclosure is the image forming apparatus according to the fourth aspect, further comprising a paper feed roll that feeds paper stored in a paper storage unit to the paper position adjustment roll; The paper position adjustment roll increases the transport speed of the paper fed by the paper feed roll and transports the paper to the first secondary transfer position.

[0012] An image forming apparatus according to a sixth aspect of the present disclosure is the image forming apparatus according to the first aspect, further comprising: a plurality of paper storage units for storing a plurality of paper sheets of different paper sizes; and a plurality of paper position adjustment rolls corresponding to the plurality of paper storage units; Of the plurality of paper storage units, the paper storage unit that is farthest from the first secondary transfer position is set to store paper of a large size. [Effects of the Invention]

[0013] According to the image forming apparatus of the first aspect of the present disclosure, it is possible to prevent fluctuations in the transport speed when the paper passes through the paper position adjustment roll from being transmitted to two secondary transfer positions simultaneously.

[0014] According to the image forming apparatus of the second aspect of the present disclosure, it is possible to prevent fluctuations in the conveyance speed when the paper passes through the fixing unit from being transmitted to two secondary transfer positions simultaneously.

[0015] According to the image forming apparatus of the third aspect of the present disclosure, it is possible to prevent fluctuations in the conveying speed when the conveying speed decreases as the paper passes through the fixing unit from being transmitted to two secondary transfer positions simultaneously.

[0016] According to the image forming apparatus of the fourth aspect of the present disclosure, even when the smallest paper size is used, it is possible to prevent the paper from falling off between the paper position adjustment roll and the first secondary transfer position.

[0017] According to the image forming apparatus of the fifth aspect of the present disclosure, it is possible to prevent fluctuations in the transport speed when the paper passes through the paper feed roll and the paper position adjustment roll from being transmitted to two secondary transfer positions simultaneously.

[0018] According to the image forming apparatus of the sixth aspect of the present disclosure, when multiple sheets of paper with different paper sizes are used, it is possible to make the distance between the paper position adjustment roll and the second secondary transfer position longer than the maximum paper length. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a diagram illustrating a configuration of an image forming apparatus 10 according to an embodiment of the present disclosure. [Figure 2]10A and 10B are diagrams for explaining the configuration of image forming units 32P, 32S, 32G, and 32Gr, and the configuration of image forming units 52Y, 52M, 52C, and 52K. [Figure 3] FIG. 2 is a diagram illustrating the configuration of a control device 80 that controls the operation of the image forming apparatus 10. [Figure 4] 10A and 10B are diagrams for explaining the mechanism by which positional deviation occurs when speed fluctuation of the paper PP is transmitted to two secondary transfer positions TJ2 and TK2 simultaneously. [Figure 5] 10A and 10B are diagrams illustrating an example of misregistration between colors that occurs at two secondary transfer positions TJ2 and TK2. [Figure 6] 10 is a diagram showing the positional relationship between the registration roll 15 and the secondary transfer position TK2. FIG. [Figure 7] 10 is a diagram showing the positional relationship between the fixing roll 16 and the secondary transfer position TJ2. FIG. [Figure 8] 10 is a diagram showing the positional relationship between the registration roll 15 and the secondary transfer position TJ2. FIG. [Figure 9] FIG. 1 is a diagram showing an example of a configuration in which a paper feeder 100 is retrofitted to an image forming apparatus 10. DETAILED DESCRIPTION OF THE INVENTION

[0020] Next, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0021] [Image forming equipment] FIG. 1 is a diagram showing a configuration of an image forming apparatus 10 according to an embodiment of the present disclosure.

[0022] As shown in FIG. 1, the image forming device 10 includes a paper storage section 12 in which paper PP is stored, a transport section 11 that transports the paper PP along a transport path 19, and an image forming unit 30 and an image forming unit 50 that form a toner image to be transferred onto the paper PP.

[0023] The paper 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.

[0024] The transport section 11 includes, in order from the upstream side in the transport direction, a delivery roll 13, a paper feed roll 14, a registration roll 15, a transport device 20, a fixing section 18, and a discharge roll 17.

[0025] The delivery roll 13 delivers the paper PP stored in the paper storage unit 12 to a transport path 19 that constitutes the transport unit 11. The paper feed roll 14 feeds the paper PP stored in the paper storage unit 12 along the transport path 19 to the registration roll 15.

[0026] The registration rolls 15 increase the transport speed of the sheet PP fed by the paper feed rolls 14 and transport it to a secondary transfer position TJ2, which will be described later. The registration rolls 15 sandwich the sheet PP and transport it downstream in the transport direction. In this way, the registration rolls 15 are paper position adjustment rolls that transport the sheet PP fed from the paper storage unit 12 to the secondary transfer position TJ2, where secondary transfer is performed by the secondary transfer unit 74, at a predetermined timing.

[0027] The transport device 20 transfers the toner images formed by the image forming units 30 and 50 onto the paper PP, and transports the paper PP downstream in the transport direction along the transport path 19. Details of the transport device 20 will be described later.

[0028] The fixing unit 18 has two fixing rolls 16, and as the paper PP passes between the two fixing rolls 16, the paper PP onto which the toner image has been transferred is heated and pressurized, thereby fixing the toner image to the paper PP. The position where the toner image is fixed to the paper PP by the two fixing rolls 16 is called the fixing position.

[0029] The discharge rollers 17 discharge the paper PP onto which the toner image has been fixed by the fixing unit 18 to the discharge unit 9.

[0030] 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.

[0031] The image forming unit 50 forms toner images of the basic colors of yellow (Y), magenta (M), cyan (C), and black (K).

[0032] The image forming unit 30 forms toner images in special colors other than the basic colors. The image forming unit 30 includes four image forming sections 32 and an endless intermediate transfer belt 40. The toner images formed by the four image forming sections 32 are transferred to the intermediate transfer belt 40, which is mounted so as to be rotatable counterclockwise when viewed from the front in FIG. 1.

[0033] Image forming units 32 include image forming unit 32P that forms a fluorescent pink (P) toner image, image forming unit 32S that forms a silver (S) toner image, image forming unit 32G that forms a gold (G) toner image, and image forming unit 32Gr that forms a fluorescent green (Gr) toner image. These four image forming units 32 are arranged in the following order from the upstream side in the rotation direction of intermediate transfer belt 40 (the side closer to support roll 44, described later). Image forming units 32P, 32S, 32G, and 32Gr have photoconductors 33P, 32S, 32G, and 32Gr, respectively.

[0034] In addition, when there is no need to distinguish between P, S, G, and Gr, they will be omitted.

[0035] 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.

[0036] The image forming unit 50 has the same configuration as the image forming unit 30 described above, except that the color of the image formed is different.

[0037] 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.

[0038] 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.

[0039] 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. In other words, within the image forming unit 52, image forming unit 52K is arranged furthest downstream in the rotation direction. The image forming units 52Y, 52M, 52C, and 52K have photoconductors 53Y, 53M, 53C, and 53K, respectively.

[0040] It should be noted that when there is no need to distinguish between Y, M, C, and K, they are omitted.

[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 primary transfer positions TY1, TM1, TC1, and TK1, respectively.

[0042] Next, the configuration of image forming sections 32P, 32S, 32G, and 32Gr will be described with reference to Fig. 2. The configuration of image forming sections 52Y, 52M, 52C, and 52K in image forming unit 50 will also be described.

[0043] 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.

[0044] 2, the image forming unit 52 includes a photoconductor 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 the developing roll 59.

[0045] Next, the transport device 20 will be described in detail.

[0046] As shown in FIG. 1, the conveying device 20 includes an endless conveying belt 21, support rolls 22 and 23 that support the conveying belt 21, and secondary transfer rolls 24 and 25 that are positioned opposite the backup rolls 42 and 62 across the intermediate transfer belts 40 and 60.

[0047] 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.

[0048] 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.

[0049] A transfer bias is applied to each of the secondary transfer rolls 24 and 25.

[0050] 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.

[0051] As described above, image forming unit 30 includes four image forming sections 33P, 33S, 33G, and 33Gr, and intermediate transfer belt 40 onto which toner images formed by these four image forming sections 33P, 33S, 33G, and 33Gr are primarily transferred. Image forming unit 50 is located downstream of image forming unit 30 in the paper transport direction and includes four image forming sections 53Y, 53M, 53C, and 53K, and intermediate transfer belt 60 onto which toner images formed by these four image forming sections 53 are primarily transferred. Secondary transfer section 74 is located corresponding to image forming unit 30 and performs secondary transfer of the toner image formed on intermediate transfer belt 40 onto paper PP transported on the paper transport path. Secondary transfer section 76 is located corresponding to image forming unit 50 and performs secondary transfer of the toner image formed on intermediate transfer belt 60 onto paper PP transported on the paper transport path.

[0052] [Control device] Next, the control device 80 that controls the operation of the image forming apparatus 10 will be described with reference to FIG.

[0053] As shown in FIG. 3, the control device 80 is electrically connected to the image forming unit 30, the image forming unit 50, the conveying section 11, the communication section 90, and the like.

[0054] 3, the control device 80 has a CPU 81 (Central Processing Unit), a ROM 82 (Read Only Memory), a RAM 83 (Random Access Memory), a storage device 85 such as a hard disk drive, and an input / output interface (abbreviated as I / O) 84 that inputs and outputs data to and from each device via a network. These components are connected to one another via a control bus.

[0055] 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 printing processing according to the image formation control program (not shown).

[0056] In addition, the image forming unit 30, the image forming unit 50, the conveying unit 11, the communication unit 90, etc. are connected to the I / O 84. The communication unit 90 is an interface for mutual data communication between the image forming apparatus 10 and a terminal device such as a personal computer.

[0057] The control device 80 performs various controls to form a toner image on the intermediate transfer belt 40 by the image forming section 32 of each color of the image forming unit 30. Similarly, the control device 80 performs various controls to form a toner image on the intermediate transfer belt 60 by the image forming section 52 of each color of the image forming unit 50.

[0058] The control device 80 also controls the developing biases applied to the developing rolls 39 and 59 of the developing devices 36 and 56. The control device 80 also controls the transfer biases applied to the secondary transfer rolls 24 and 25.

[0059] The control device 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 .

[0060] [Image forming process] Next, an outline of the image forming process in the image forming apparatus 10 will be described.

[0061] First, the control device 80 controls each image forming section 32 so that a toner image is formed on the intermediate transfer belt 40 of the image forming unit 30. Similarly, the control device 80 controls each image forming section 52 so that a toner image is formed on the intermediate transfer belt 60 of the image forming unit 50.

[0062] Specifically, the control device 80 applies a voltage to the charging members 34, 54, which then charge the surfaces of the photoconductors 33, 53 to a predetermined potential. Next, based on image data acquired via the communication unit 90, the control device 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, thereby forming electrostatic latent images. As a result, electrostatic latent images corresponding to the image data are formed on the surfaces of the photoconductors 33, 53.

[0063] Next, the control device 80 causes 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 device 80 causes 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.

[0064] In this way, in the image forming unit 30, a toner image in which, for example, fluorescent pink (P), silver (S), gold (G), and fluorescent green (Gr) 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 (Y), magenta (M), cyan (C), and black (K) toners are superimposed is formed on the intermediate transfer belt 60.

[0065] Here, the sheet of paper PP sent from the paper storage section 12 to the transport path 19 by the delivery roll 13 has its transport timing adjusted by the two registration rolls 15 under the control of the control device 80, and is then sent to the secondary transfer position TJ2. At this secondary transfer position TJ2, the sheet of paper PP is transported between the backup roll 42 and the secondary transfer roll 24, so that the toner image on the outer peripheral surface of the intermediate transfer belt 40 is transferred onto the sheet of paper PP. Then, the sheet of paper PP with the toner image transferred thereto is transported downstream in the transport direction, and reaches the secondary transfer position TK2 on the downstream side in the transport direction.

[0066] At this time, the control device 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 paper PP transported from the upstream side in the transport direction.

[0067] 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 fixing roll 16 of the fixing section 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.

[0068] With the above-described configuration, the image forming apparatus 10 of this embodiment can form images using not only the basic CMYK toners but also toners in special colors other than CMYK. This image forming apparatus 10 is configured to form toner images on paper using two image forming units 30, 50, each of which includes a plurality of image forming sections 32, 52 that form toner images. Each image forming unit 30, 50 primarily transfers the toner images formed by the plurality of image forming sections 32, 52 onto intermediate transfer belts 40, 60, which serve as intermediate transfer bodies. The toner images on the intermediate transfer belts 40, 60 are then secondarily transferred onto paper PP transported by the transport device 20. In other words, when a toner image is formed on paper using the two image forming units 30, 50, the secondary transfer occurs at two secondary transfer positions TJ2, TK2.

[0069] Here, the sheet PP transported to the secondary transfer positions TJ2, TK2 needs to be transported at a predetermined timing synchronized with the image formation timing. Therefore, the sheet transported by the sheet feed rolls 14 has its transport timing adjusted by a sheet position adjustment roll called a registration roll 15, and is transported to the secondary transfer positions TJ2, TK2. If the transport speed by the sheet feed rolls 14 and the transport speed by the registration rolls 15 differ, fluctuations in the transport speed occur when the sheet PP passes through the sheet feed rolls 14 and the registration rolls 15.

[0070] However, if a fluctuation in the transport speed of the paper PP occurs while secondary transfer is being performed on the paper at the two secondary transfer positions TJ2 and TK2, this fluctuation in the transport speed is transmitted to both secondary transfer positions TJ2 and TK2 simultaneously. This fluctuation in the transport speed is then transmitted simultaneously to the multiple image forming sections 32 and 52 via the intermediate transfer belts 40 and 60 of the two image forming units 30 and 50. As a result, the image formation in the multiple image forming sections 32 and 52 is affected, and there is a possibility that the formed images will be misaligned.

[0071] The mechanism by which misregistration occurs when speed fluctuations in the paper PP are transmitted to the two secondary transfer positions TJ2 and TK2 simultaneously will be described with reference to Fig. 4. Note that Fig. 4 shows only the structures that are necessary for the explanation of the structure that constitutes the image forming apparatus 10, and other structures are omitted for the explanation. This also applies to the figures in the following explanation.

[0072] The sheet of paper PP sent out from the paper storage section 12 is transported to the registration rolls 15 at an increased transport speed by the paper feed rolls 14. However, the registration rolls 15 transport the transported sheet of paper PP to the secondary transfer position TJ2 of the transport device 20 at a predetermined transport timing. The registration rolls 15 are set to have a transport speed slightly faster than that of the paper feed rolls 14. However, the transport speed at the secondary transfer position TJ2 is set slower than the transport speed of the registration rolls 15. Therefore, the transport speed of the sheet of paper PP is reduced when it passes through the registration rolls 15 and it is transported to the secondary transfer position TJ2.

[0073] As described above, fluctuations in the conveyance speed occur when the sheet of paper PP passes through the registration roll 15. Therefore, when the sheet of paper PP reaches the two secondary transfer positions TJ2 and TK2 while still passing through the registration roll 15, the speed fluctuations of the sheet of paper PP are transmitted from the two secondary transfer positions TJ2 and TK2 to the intermediate transfer belts 40 and 60, respectively. As a result, the conveyance speed fluctuations are also transmitted to the primary transfer positions TP1, TS1, TG1, and TGr1, and the primary transfer positions TY1, TM1, TC1, and TK1 in the image forming units 30 and 50. Therefore, the speed fluctuations are also transmitted to the photoconductors 33P, 33S, 33G, and 33Gr, and the photoconductors 53Y, 53M, 53C, and 53K, causing misregistration of the overlapping positions of the toner images of each color. Furthermore, because the timing of secondary transfer at the two secondary transfer positions TJ2 and TK2 is different, different colors will experience different misregistrations at the two secondary transfer positions TJ2 and TK2.

[0074] An example of misregistration between colors that occurs in this way is shown in Figure 5. Figure 5(A) is a diagram showing how misregistration occurs between YMCK colors. Figure 5(B) is a diagram showing how misregistration occurs between the spot colors PSGGr. Referring to Figure 5, it can be seen that misregistration occurs where the colors overlap due to speed fluctuations being transmitted to photoconductors 33P, 33S, 33G, 33Gr and 53Y, 53M, 53C, 53K via intermediate transfer belts 40 and 60.

[0075] Therefore, the image forming apparatus 10 of this embodiment is configured as shown in Fig. 6 to prevent fluctuations in the conveying speed when the sheet PP passes through the registration rolls 15 from being transmitted to the two secondary transfer positions TJ2 and TK2 simultaneously. Fig. 6 is a diagram showing the positional relationship between the registration rolls 15 and the secondary transfer position TK2.

[0076] As can be seen from Figure 6, the distance between the registration roll 15, which is a paper position adjustment roll, and the secondary transfer position TK2 where secondary transfer is performed by the secondary transfer unit 76 is configured to be longer than the maximum paper length, which is the length in the transport direction of the largest paper size that may be used.

[0077] For example, let's say that the largest paper size that may be used is A4 size (210 mm x 297 mm). In this case, the length of A4 size paper in the transport direction is 297 mm, so the maximum paper length is also 297 mm. Therefore, in this case, the positional relationship between the image forming unit 50 and the registration roll 15 is set so that the distance between the registration roll 15 and the secondary transfer position TK2 is 297 mm or more. Note that the paper PP in FIG. 6 indicates the case where the paper size is A4 size.

[0078] With this configuration, as shown in FIG. 6, while the sheet of paper PP is sandwiched between the registration rolls 15, the leading edge of the sheet of paper PP does not reach the secondary transfer position TK2.

[0079] Therefore, the speed fluctuation that occurs when the paper PP passes through the registration rolls 15 is not transmitted to the secondary transfer position TK2. As a result, the speed fluctuation is not transmitted to the photoconductors 53Y, 53M, 53C, and 53K in the image forming unit 50.

[0080] In other words, by preventing the speed fluctuations when the paper PP passes through the registration roll 15 from being transmitted to the two secondary transfer positions TJ2 and TK2 simultaneously, misalignment between the colors of the toner images formed in the image forming unit 50 is suppressed.

[0081] Even with the above configuration, speed fluctuations that occur when the paper PP passes through the registration roll 15 are transmitted to the secondary transfer position TJ2. However, there is a technology that corrects misregistration between colors by performing image processing on image data for forming a toner image and correcting the position of the toner image for each color. Using such a technology, it is possible to correct misregistration that occurs in one area on the paper. However, even with such a technology, it is difficult to correct misregistration that occurs in two or more areas on the paper. Therefore, if speed fluctuations that occur when the paper PP passes through the registration roll 15 are simultaneously transmitted to the two secondary transfer positions TJ2 and TK2, causing misregistration in two areas on the paper, it is difficult to correct the misregistration.

[0082] In other words, by limiting the secondary transfer position to which the speed fluctuations that occur when the paper PP passes through the registration roll 15 are transmitted to one location, it is possible to suppress misregistration between colors that occurs on the paper.

[0083] Furthermore, as shown in FIG. 4, if the leading edge of the sheet PP reaches the secondary transfer position TK2 before the sheet PP has finished passing through the registration rolls 15, the sheet PP will be pressed down at three locations: the registration rolls 15 and the secondary transfer positions TJ2 and TK2. Therefore, when speed fluctuations that occur when the sheet PP passes through the registration rolls 15 are transmitted to the two secondary transfer positions TJ2 and TK2, it becomes difficult to predict what type of misalignment will occur due to the interaction between the two secondary transfer positions TJ2 and TK2. Therefore, when speed fluctuations that occur when the sheet PP passes through the registration rolls 15 are transmitted to the two secondary transfer positions TJ2 and TK2 simultaneously, it becomes more difficult to correct misalignment compared to when the speed fluctuations are transmitted to only one secondary transfer position TJ2.

[0084] The fixing unit 18 fixes the toner image on the paper PP after secondary transfer by the secondary transfer unit 76. At this time, the fixing unit 18 fixes the toner image on the paper PP in a state where the conveying speed of the paper PP conveyed along the paper conveyance path is reduced at the fixing position.

[0085] Since speed fluctuations also occur in the fixing unit 18 in this way, the image forming apparatus 10 of this embodiment is configured so that the distance between the fixing position where the fixing unit 18 fixes the toner image to the paper and the secondary transfer position TJ2 where the secondary transfer is performed by the secondary transfer unit 74 is longer than the maximum paper length, as shown in Fig. 7. Fig. 7 is a diagram showing the positional relationship between the fixing roll 16 of the fixing unit 18 and the secondary transfer position TJ2.

[0086] Referring to FIG. 7, it can be seen that this configuration prevents speed fluctuations when the sheet of paper PP passes through the fixing unit 18 from being transmitted to the two secondary transfer positions TJ2 and TK2 simultaneously.

[0087] Next, the positional relationship between the registration rolls 15 and the secondary transfer position TJ2 is shown in Figure 8. If the position of the registration rolls 15 is set too low in an attempt to increase the distance between the registration rolls 15 and the secondary transfer position TJ2, the distance between the registration rolls 15 and the secondary transfer position TJ2 will also increase. If the distance between the registration rolls 15 and the secondary transfer position TJ2 becomes too long, there is a possibility that the sheet of paper PP will drop off between the registration rolls 15 and the secondary transfer position TJ2 when a short sheet of paper PP is being transported.

[0088] Therefore, in the image forming apparatus 10 of this embodiment, the distance between the registration roll 15 and the secondary transfer position TJ2 where the secondary transfer is performed by the secondary transfer unit 74 is set to be shorter than the minimum paper length, which is the length in the conveying direction of the smallest paper size among the papers that may be used.

[0089] For example, let's say that the smallest paper size that may be used is L-size photo paper (89 mm x 127 mm). In this case, the length of L-size photo paper in the transport direction is 127 mm, so the minimum paper length is also 127 mm. Therefore, in this case, the positional relationship between the image forming unit 30 and the registration roll 15 is set so that the distance between the registration roll 15 and the secondary transfer position TJ2 is shorter than 127 mm. Note that the paper PP in FIG. 8 indicates a case where the paper size is L-size photo paper.

[0090] Next, a configuration example in which the sheet feeding device 100 is retrofitted to the image forming apparatus 10 is shown in FIG.

[0091] The paper feeder 100 can be installed as an option after the image forming apparatus 10 is installed. The paper feeder 100 includes a paper storage section 12A, a delivery roll 13A, a paper feed roll 14A, and a registration roll 15A. In this configuration in which the paper feeder 100 is installed after the image forming apparatus 10 is installed, the image forming apparatus 10 is provided with two paper storage sections 12, 12A that store multiple sheets of paper of different sizes, and multiple registration rolls 15, 15A that correspond to the two paper storage sections 12, 12A.

[0092] When paper is fed to image forming apparatus 10 using such an additional paper feeder 100, the paper storage unit 12, 12A is set to store larger paper sizes in the paper storage unit that is farther from secondary transfer position TJ2 than the multiple paper storage units 12, 12A. By setting it in this way, when multiple sheets of different sizes are used, the distance between the registration rolls and secondary transfer position TJ2 can be made longer than the maximum paper length.

[0093] For example, if A3 size paper is stored in the paper storage section 12A on the paper feeder 100 side, it becomes easy to make the distance between the resist roll 15A and the secondary transfer position TJ2 longer than the length of the A3 size paper in the transport direction.

[0094] In each of the above embodiments, 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.).

[0095] Furthermore, the operations of the processor in each of the above embodiments may be performed not only by a single processor but also by multiple processors located at physically separate locations working together. Furthermore, the order of the operations of the processor is not limited to the order described in each of the above embodiments and may be changed as appropriate.

[0096] In this embodiment, the term "system" includes both a system made up of multiple devices and a system made up of a single device.

[0097] [Note] Preferred embodiments of the present disclosure will be described below.

[0098] (((1))) a first image forming unit having a plurality of first image forming sections and a first intermediate transfer body onto which the toner images formed by the plurality of first image forming sections are primarily transferred; a second image forming unit provided downstream of the first image forming unit in a paper transport direction, the second image forming unit having a plurality of second image forming units and a second intermediate transfer body onto which toner images formed by the plurality of second image forming units are primarily transferred; a first secondary transfer unit provided corresponding to the first image forming unit, which performs a second transfer of the toner image formed on the first intermediate transfer body onto a sheet of paper transported on a paper transport path; a second secondary transfer unit provided corresponding to the second image forming unit, which performs a second transfer of the toner image formed on the second intermediate transfer body onto a sheet of paper transported on a paper transport path; a paper position adjustment roll that transports the fed paper at a predetermined timing to a first secondary transfer position where secondary transfer is performed by the first secondary transfer unit, a distance between the paper position adjustment roll and a second secondary transfer position where secondary transfer is performed by the second secondary transfer unit is longer than a maximum paper length, which is the length in the transport direction of a paper with the largest paper size among paper that may be used; Image forming device.

[0099] (((2))) a fixing unit that fixes the toner image on the paper after the second secondary transfer by the second secondary transfer unit, a distance between a fixing position where the fixing unit fixes the toner image onto the paper and a first secondary transfer position where the first secondary transfer unit performs secondary transfer is longer than the maximum paper length; The image forming apparatus according to (((1))).

[0100] (((3))) the fixing unit fixes the toner image onto the paper in a state where the conveying speed of the paper conveyed through the paper conveyance path is reduced at the fixing position; The image forming apparatus according to (((2))).

[0101] (((4))) a distance between the paper position adjustment roll and a first secondary transfer position where secondary transfer is performed by the first secondary transfer unit is shorter than a minimum paper length, which is the length in the transport direction of a paper with the smallest paper size among paper that may be used; The image forming apparatus according to any one of (((1))) to (((3))).

[0102] (((5))) a paper feed roll that feeds paper stored in a paper storage unit to the paper position adjustment roll; the paper position adjustment roll increases the transport speed of the paper fed by the paper feed roll and transports it to the first secondary transfer position; The image forming apparatus according to (((4))).

[0103] (((6))) a plurality of paper storage sections for storing a plurality of paper sheets of different paper sizes, and a plurality of paper position adjustment rolls corresponding to the plurality of paper storage sections; Among the plurality of paper storage units, a paper storage unit that is farther away from the first secondary transfer position is set to store paper of a larger size. The image forming apparatus according to any one of (((1))) to (((5))).

[0104] The effects of the configuration described above will be described below.

[0105] According to the image forming apparatus (((1))), it is possible to prevent fluctuations in the transport speed when the paper passes through the paper position adjusting roll from being transmitted to two secondary transfer positions at the same time.

[0106] According to the image forming apparatus of (((2))), it is possible to prevent fluctuations in the conveyance speed when the paper passes through the fixing unit from being transmitted to two secondary transfer positions at the same time.

[0107] According to the image forming apparatus (((3))), it is possible to prevent fluctuations in the conveying speed when the conveying speed decreases as the paper passes through the fixing unit from being transmitted to two secondary transfer positions simultaneously.

[0108] According to the image forming device (((4))), even when the smallest paper size is used, it is possible to prevent the paper from falling off between the paper position adjustment roll and the first secondary transfer position.

[0109] According to the image forming apparatus of (((5))), it is possible to prevent fluctuations in the conveyance speed when the paper passes through the paper feed roll and the paper position adjustment roll from being transmitted to two secondary transfer positions at the same time.

[0110] According to the image forming apparatus (((6))), when multiple sheets of paper with different paper sizes are used, it is possible to make the distance between the paper position adjustment roll and the second secondary transfer position longer than the maximum paper length. [Explanation of symbols]

[0111] 9 Discharge section 10 Image forming device 10A Image forming device main body 11 Conveyor 12, 12A Paper storage section 13, 13A Delivery roll 14, 14A paper feed roll 15, 15A resist roll 16 Fixing roll 17 Ejection roll 18 Fixing section 19 Transport Route 20. Conveyor 21 Conveyor belt 22, 23 Support roll 24, 25 Secondary transfer roll 30 Image forming unit 32 Image forming unit 32P, 32S, 32G, 32Gr image forming section 33P, 33S, 33G, 33Gr photoconductor 34 Charging member 35 Exposure equipment 36 Developing device 37P, 37S, 37G, 37Gr primary transfer roll 39 Developing Roll 40 Intermediate transfer belt 42 Backup Roll 44 Support Roll 50 Image forming unit 52Y, 52M, 52C, 52K Image forming section 53Y, 53M, 53C, 53K photoconductor 54 Charging member 55 Exposure equipment 56 Developing device 57Y, 57M, 57C, 57K Primary transfer roll 59 Developing Roll 60 Intermediate transfer belt 62 Backup Roll 64 Support Roll 70, 72 Primary transfer section 74, 76 Secondary transfer section 80 Control device 81 CPU 82 ROM 83 RAM 84 I / O (input / output interface) 85 Storage device 90 Communications Department 100 Paper feeder PP paper TJ2, TK2 secondary transfer position TP1, TS1, TG1, TGr1 primary transcription position TY1, TM1, TC1, TK1 primary transcription position

Claims

1. a first image forming unit having a plurality of first image forming sections and a first intermediate transfer body onto which the toner images formed by the plurality of first image forming sections are primarily transferred; a second image forming unit provided downstream of the first image forming unit in a paper transport direction, the second image forming unit having a plurality of second image forming units and a second intermediate transfer body onto which toner images formed by the plurality of second image forming units are primarily transferred; a first secondary transfer unit provided corresponding to the first image forming unit, which performs a second transfer of the toner image formed on the first intermediate transfer body onto a sheet of paper transported on a paper transport path; a second secondary transfer unit provided corresponding to the second image forming unit, which performs a second transfer of the toner image formed on the second intermediate transfer body onto a sheet of paper transported on a paper transport path; a paper position adjustment roll that transports the fed paper at a predetermined timing to a first secondary transfer position where the first secondary transfer unit performs secondary transfer, a distance between the paper position adjustment roll and a second secondary transfer position where secondary transfer is performed by the second secondary transfer unit is longer than a maximum paper length, which is the length in the transport direction of a paper with a largest paper size among papers that may be used; Image forming device.

2. a fixing unit that fixes the toner image on the paper after the second secondary transfer by the second secondary transfer unit, a distance between a fixing position where the fixing unit fixes the toner image onto the paper and a first secondary transfer position where the first secondary transfer unit performs secondary transfer is longer than the maximum paper length; The image forming apparatus according to claim 1 .

3. the fixing unit fixes the toner image onto the paper in a state where the conveying speed of the paper conveyed through the paper conveyance path is reduced at the fixing position; The image forming apparatus according to claim 2 .

4. a distance between the paper position adjustment roll and a first secondary transfer position where secondary transfer is performed by the first secondary transfer unit is shorter than a minimum paper length, which is the length in the transport direction of a paper with a smallest paper size among papers that may be used; The image forming apparatus according to claim 1 .

5. a paper feed roll that feeds paper stored in a paper storage unit to the paper position adjustment roll; the paper position adjustment roll increases the transport speed of the paper fed by the paper feed roll and transports the paper to the first secondary transfer position; The image forming apparatus according to claim 4 .

6. a plurality of paper storage sections for storing a plurality of paper sheets of different paper sizes, and a plurality of paper position adjustment rolls corresponding to the plurality of paper storage sections; Among the plurality of paper storage units, a paper storage unit that is farther away from the first secondary transfer position is set to store paper of a larger size. The image forming apparatus according to claim 1 .

Images