Image forming apparatus

Abstract

An image forming apparatus includes: a first image forming unit including a plurality of first image forming sections and a first intermediate transfer body to which a toner image formed by the plurality of first image forming sections is transferred at a time; a second image forming unit that is provided downstream of the first image forming unit in a sheet conveyance direction, and that has a plurality of second image forming sections and a second intermediate transfer body to which the toner images formed by the plurality of second image forming sections are transferred at a time; a first secondary transfer section that is provided corresponding to the first image forming unit and that secondarily transfers the toner image formed on the first intermediate transfer body onto a sheet conveyed on a sheet conveyance path; a second secondary transfer section that is provided corresponding to the second image forming unit and that secondarily transfers the toner image formed on the second intermediate transfer body onto a sheet conveyed on a sheet conveyance path; and a sheet position adjusting roller that conveys the supplied sheet at a predetermined timing to a first secondary transfer position at which the sheet is secondarily transferred by the first secondary transfer section. The distance between the sheet position adjustment roller and a second secondary transfer position at which secondary transfer is performed by the second secondary transfer section is longer than the maximum sheet length, which is the length of the sheet having the largest sheet size in the conveyance direction, among the sheets that are likely to be used.

Description

Technical Field

[0001] This invention relates to an image forming apparatus. Background Technology

[0002] Patent document 1 discloses a printing apparatus in which a plurality of engine units are stacked in the vertical direction and a common discharge conveying mechanism, a speed switching control mechanism, a high-speed rotation holding control mechanism and a timing limiting mechanism are provided. The apparatus is configured such that each engine unit can handle the amount of printing data and can discharge the printed paper discharged from each engine unit at high speed to a common paper receiving unit through its own conveying mechanism or the common discharge conveying mechanism.

[0003] Patent Document 2 discloses an image forming apparatus in which, for example, a plurality of image forming units are arranged side by side in a longitudinal direction, and toner images are sequentially transferred onto transfer material at the transfer sites of each image forming unit, a transfer mechanism is provided in each image forming unit, and the distance on the transfer material transport path between the interlocking transfer mechanisms on the inlet side and the outlet side is defined as a dimension shorter than the transport direction length of the transfer material of the standard size, or the transfer mechanism interlocks at least across a plurality of image forming units without causing the transfer material of the minimum size to be interlocked by the interlocking transfer mechanisms on the inlet side and the outlet side at the same time.

[0004] Patent Document 1: Japanese Patent Application Publication No. 8-211673

[0005] Patent Document 2: Japanese Patent Application Publication No. 9-325560

[0006] In recent years, to expand the color gamut of images formed by image forming apparatuses, not only toners based on the CMYK basic colors can be used, but also toners of special colors other than CMYK can be used for image formation. In such image forming apparatuses, a structure is sometimes used where two image forming units, each equipped with a plurality of image forming sections for forming toner images, are used to form toner images on paper. In each image forming unit, the toner image formed by the plurality of image forming sections is transferred once to an intermediate transfer body, and the toner image on the intermediate transfer body is then transferred a second time to the paper being transported along the paper transport path. That is, when using two image forming units to form toner images on paper, a second transfer is performed at two secondary transfer locations. Summary of the Invention

[0007] The purpose of this invention is to provide an image forming apparatus that can prevent changes in the conveying speed of paper as it passes through the paper position adjustment roller from being transmitted to two secondary transfer positions simultaneously.

[0008] The image forming apparatus of the first aspect of the present invention includes:

[0009] The first image forming unit has a plurality of first image forming sections and a first intermediate transfer body, wherein the first intermediate transfer body transfers a tonal image formed by the plurality of the first image forming sections at one time;

[0010] The second image forming unit is located downstream of the first image forming unit in the paper transport direction, and has a plurality of second image forming sections and a second intermediate transfer body, wherein the second intermediate transfer body transfers a tonal image formed by the plurality of second image forming sections at one time.

[0011] The first secondary transfer unit is provided corresponding to the first image forming unit, and transfers the toner image formed on the first intermediate transfer body to the paper conveyed on the paper transport path.

[0012] The second secondary transfer unit, corresponding to the second image forming unit, performs a secondary transfer of the toner image formed on the second intermediate transfer body onto the paper being transported along the paper transport path; and

[0013] The paper position adjustment roller conveys the supplied paper to the first secondary transfer position where the second secondary transfer is performed by the first secondary transfer unit at a predetermined time.

[0014] The distance between the paper position adjustment roller and the second transfer position where the second transfer is performed by the second transfer unit is longer than the length of the largest paper in the conveying direction, i.e., the maximum paper length, among the possible paper sizes.

[0015] The image forming apparatus of the second aspect of the present invention, in addition to the image forming apparatus of the first aspect, includes a fixing unit, which fixes the toner image on the paper after it has been transferred twice by the second secondary transfer unit onto the paper.

[0016] The distance between the fixing position of the tonal image on the paper by the fixing unit and the first secondary transfer position of the second secondary transfer unit is longer than the maximum paper length.

[0017] The image forming apparatus of the third aspect of the present invention is in the image forming apparatus of the second aspect.

[0018] The fixing unit fixes the toner image on the paper at a state where the conveying speed of the paper being conveyed on the paper conveying path is reduced at the fixing position.

[0019] The image forming apparatus of the fourth aspect of the present invention is an image forming apparatus of any one of the first to third aspects.

[0020] The distance between the paper position adjustment roller and the first secondary transfer position where the second transfer is performed by the first secondary transfer unit is shorter than the length of the smallest paper in the conveying direction, i.e., the minimum paper length, among the papers that may be used.

[0021] The image forming apparatus of the fifth aspect of the present invention, in addition to the image forming apparatus of the fourth aspect, includes a paper feed roller that supplies paper stored in a paper storage section to the paper position adjusting roller.

[0022] The paper position adjustment roller increases the conveying speed of the paper supplied by the paper feed roller and conveys it to the first secondary transfer position.

[0023] The image forming apparatus of the sixth aspect of the present invention, in any one of the image forming apparatuses of the first to fifth aspects, includes: a plurality of paper storage sections for storing a plurality of papers of different sizes; and a plurality of paper position adjusting rollers corresponding to the plurality of paper storage sections.

[0024] The image forming apparatus is configured to store large-sized sheets of paper in the paper storage section that is far from the first secondary transfer position among the plurality of paper storage sections.

[0025] Invention Effects

[0026] According to the first aspect of the image forming apparatus of the present invention, it is possible to prevent changes in the conveying speed of the paper as it passes through the paper position adjusting roller from being simultaneously transmitted to two secondary transfer positions.

[0027] According to the second aspect of the image forming apparatus of the present invention, it is possible to prevent changes in the conveying speed of the paper as it passes through the fixing section from being simultaneously transmitted to the two secondary transfer positions.

[0028] According to the third aspect of the image forming apparatus of the present invention, it is possible to prevent the change in conveying speed when the paper passes through the fixing section and the conveying speed decreases, from being transmitted to two secondary transfer positions simultaneously.

[0029] According to the fourth aspect of the image forming apparatus of the present invention, even when using paper with the smallest paper size, it is possible to prevent the paper from falling off between the paper position adjusting roller and the first secondary transfer position.

[0030] According to the fifth aspect of the image forming apparatus of the present invention, it is possible to prevent changes in the conveying speed of the paper as it passes through the paper feed roller and the paper position adjusting roller from being simultaneously transmitted to two secondary transfer positions.

[0031] According to the sixth aspect of the image forming apparatus of the present invention, when using a plurality of sheets of different sizes, the distance between the paper position adjusting roller and the second secondary transfer position is longer than the maximum paper length. Attached Figure Description

[0032] The embodiments of the present invention will be described in detail with reference to the following figures.

[0033] Figure 1 This is a diagram showing the structure of an image forming apparatus 10 according to an embodiment of the present invention;

[0034] Figure 2 This is a diagram used to illustrate the structure of image forming units 32P, 32S, 32G, and 32Gr, and the structure of image forming units 52Y, 52M, 52C, and 52K;

[0035] Figure 3 This is a diagram illustrating the structure of the control device 80 that controls the operation of the image forming apparatus 10;

[0036] Figure 4 This diagram illustrates the mechanism of misalignment that occurs when the speed variation of the paper PP is simultaneously transmitted to two secondary transfer positions TJ2 and TK2.

[0037] Figure 5 This diagram illustrates an example of misalignment between colors occurring at two secondary transfer positions, TJ2 and TK2.

[0038] Figure 6 This is a diagram showing the positional relationship between the positioning roller 15 and the secondary transfer position TK2;

[0039] Figure 7 This is a diagram showing the positional relationship between the fixing roller 16 and the secondary transfer position TJ2;

[0040] Figure 8 This is a diagram showing the positional relationship between the positioning roller 15 and the secondary transfer position TJ2;

[0041] Figure 9 This is a diagram showing a structural example when the paper feeding device 100 is subsequently installed into the image forming apparatus 10. Detailed Implementation

[0042] Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0043] [Image forming apparatus]

[0044] Figure 1 This is a diagram showing the structure of an image forming apparatus 10 as an embodiment of the present invention.

[0045] like Figure 1 As shown, the image forming apparatus 10 includes: a paper storage section 12 for holding paper PP; a conveying section 11 for conveying paper PP along a conveying path 19; and an image forming unit 30 and an image forming unit 50 for forming a tonal image transferred onto paper PP.

[0046] The paper storage section 12 can be pulled out from the image forming apparatus body 10A, which is the main body of the image forming apparatus 10, and contains paper PP.

[0047] The conveying unit 11 includes, in sequence from the upstream side of the conveying direction, an output roller 13, a paper feed roller 14, a positioning roller 15, a conveying device 20, a fixing unit 18, and an output roller 17.

[0048] The feed roller 13 feeds the paper PP stored in the paper storage section 12 to the conveying path 19 that constitutes the conveying section 11. The paper feed roller 14 feeds the paper PP stored in the paper storage section 12 to the positioning roller 15 along the conveying path 19.

[0049] The positioning roller 15 increases the conveying speed of the paper PP supplied by the paper feed roller 14 and conveys it to the secondary transfer position TJ2, which will be described later. The positioning roller 15 clamps the paper PP and conveys it downstream in the conveying direction. In this way, the positioning roller 15 is a paper position adjustment roller that conveys the paper PP supplied from the paper storage section 12 to the secondary transfer position TJ2, where the secondary transfer is performed by the secondary transfer section 74, at a predetermined time.

[0050] The conveying device 20 transfers the toner image formed by the image forming units 30 and 50 onto the paper PP, and conveys the paper PP downstream in the conveying direction along the conveying path 19. Further details about the conveying device 20 will be described later.

[0051] The fixing unit 18 has two fixing rollers 16, and the paper PP passes between the two fixing rollers 16, thereby heating and pressurizing the paper PP on which the toner image has been transferred, so that the toner image is fixed on the paper PP. In addition, the position where the toner image is fixed on the paper PP by the two fixing rollers 16 is called the fixing position.

[0052] The discharge roller 17 discharges the paper PP, which has been fixed with toner through the fixing section 18, to the discharge section 9.

[0053] The image forming unit 30 and the image forming unit 50 are arranged vertically. In this embodiment, the image forming unit 50 is positioned above the image forming unit 30. Alternatively, the image forming unit 50 may be positioned downstream of the image forming unit 30 in the paper transport direction.

[0054] In the image forming unit 50, tonal images of the basic colors yellow (Y), magenta (M), cyan (C), and black (K) are formed.

[0055] Then, in the image forming unit 30, a toner image of a special color other than the basic color is formed. The image forming unit 30 includes four image forming sections 32 and an annular intermediate transfer belt 40. The intermediate transfer belt 40 is configured to transfer the toner image formed by the four image forming sections 32, and when viewed from the front... Figure 1 It can rotate counterclockwise.

[0056] The image forming unit 32 includes an image forming unit 32P for forming a fluorescent pink (P) toner image, an image forming unit 32S for forming a silver (S) toner image, an image forming unit 32G for forming a gold (G) toner image, and an image forming unit 32Gr for forming a fluorescent green (Gr) toner image. These four image forming units 32 are arranged sequentially from the upstream side (the side closest to the support roller 44 described later) in the rotation direction of the intermediate transfer belt 40, in the order of image forming unit 32P, image forming unit 32S, image forming unit 32G, and image forming unit 32Gr. The image forming units 32P, 32S, 32G, and 32Gr each have photoreceptors 33P, 32S, 32G, and 32Gr, respectively.

[0057] Furthermore, unless it is necessary to distinguish between P, S, G, and Gr for explanation, they will be omitted from the description.

[0058] Furthermore, primary transfer rollers 37P, 37S, 37G, and 37Gr are positioned opposite each photoreceptor 33 across the intermediate transfer belt 40 to transfer the tonal image formed by the image forming unit 32 to the intermediate transfer belt 40. The intermediate transfer belt 40 is wound around a support roller 44 and a backup roller 42, which supports the intermediate transfer belt 40 and is located in the secondary transfer section 74 on the upstream side, as described later. The primary transfer section 70 is composed of the photoreceptor 33, the primary transfer roller 37, and the intermediate transfer belt 40. Primary transfer positions TP1, TS1, TG1, and TGr1 are respectively set between the photoreceptors 33P, 33S, 33G, and 33Gr and the intermediate transfer belt 40.

[0059] Except for the different colors formed in the image, the image forming unit 50 has the same structure as the aforementioned image forming unit 30.

[0060] The image forming unit 50 includes four image forming sections 52 and an intermediate transfer belt 60. The intermediate transfer belt 60 is configured to transfer the tonal image formed by the four image forming sections 52, and when viewed from the front... Figure 1 It can rotate counterclockwise.

[0061] In addition, except for the different colors formed in the image, the image forming unit 52 has the same structure as the image forming unit 32 of the image forming unit 30. Furthermore, the intermediate transfer belt 60 and the primary transfer roller 57 (described later) also have the same structure as the intermediate transfer belt 40 and primary transfer roller 37 of the image forming unit 30. Moreover, the other components constituting the image forming unit 50 are also the same as those of the image forming unit 30.

[0062] The image forming unit 52 includes an image forming unit 52Y for forming a yellow toner image, an image forming unit 52M for forming a magenta toner image, an image forming unit 52C for forming a blue-green toner image, and an image forming unit 52K for forming a black toner image. The four image forming units 52 are arranged sequentially from the upstream side of the rotation direction (the side closest to the support roller 64 described later) in the order of image forming unit 52Y, image forming unit 52M, image forming unit 52C, and image forming unit 52K. That is, in the image forming units 52, image forming unit 52K is located at the downstream end of the rotation direction. Furthermore, the image forming units 52Y, 52M, 52C, and 52K each have photosensitive elements 53Y, 53M, 53C, and 53K, respectively.

[0063] Furthermore, unless it is necessary to distinguish between Y, M, C, and K for explanation, they will be omitted from the description.

[0064] Furthermore, primary transfer rollers 57Y, 57M, 57C, and 57K are positioned opposite each photoreceptor 53, separated by the intermediate transfer belt 60. The intermediate transfer belt 60 is wound around the support roller 64 and the support roller 62 of the secondary transfer section 76 located downstream (described later). The primary transfer section 72 comprises the photoreceptor 53, the primary transfer roller 57, and the intermediate transfer belt 60. The primary transfer positions TY1, TM1, TC1, and TK1 are respectively defined between the photoreceptors 53Y, 53M, 53C, and 53K and the intermediate transfer belt 60.

[0065] Next, refer to Figure 2 The structures of image forming units 32P, 32S, 32G, and 32Gr will be described. Furthermore, the structures of image forming units 52Y, 52M, 52C, and 52K in image forming unit 50 will also be described.

[0066] like Figure 2 As shown, the image forming unit 32 includes: a photoreceptor 33; a charging member 34 that charges the surface of the photoreceptor 33; an exposure device 35 that exposes the charged photoreceptor 33 by irradiation; and a developing device 36 that develops the electrostatic latent image formed by the exposure to visualize it as a toner image. The developing device 36 has a developing roller 39 and is subjected to a developing bias voltage.

[0067] Similarly, as Figure 2 As shown, the image forming unit 52 includes a photosensitive element 53, a charged component 54, an exposure device 55, and a developing device 56. The developing device 56 has a developing roller 59 and is subjected to a developing bias voltage.

[0068] Next, the details of the transmission device 20 will be explained.

[0069] like Figure 1 As shown, the conveying device 20 includes: an annular conveyor belt 21; support rollers 22 and 23 supporting the conveyor belt 21; and secondary transfer rollers 24 and 25, which are arranged opposite to the support rollers 42 and 62 across the intermediate transfer belts 40 and 60.

[0070] The secondary transfer roller 24 clamps the paper PP and the conveyor belt 21 between the secondary transfer roller 24 and the support roller 42, transferring the toner image formed on the intermediate transfer belt 40 of the image forming unit 30 onto the paper PP. Similarly, the secondary transfer roller 25 clamps the paper PP and the conveyor belt 21 between the secondary transfer roller 25 and the support roller 62, transferring the toner image formed on the intermediate transfer belt 60 of the image forming unit 50 onto the paper PP.

[0071] Furthermore, the secondary transfer section 74 is composed of a support roller 42, a secondary transfer roller 24, and an intermediate transfer belt 40. Also, the secondary transfer section 76 is composed of a support roller 62, a secondary transfer roller 25, and an intermediate transfer belt 60.

[0072] Apply transfer bias pressure to the secondary transfer rollers 24 and 25 respectively.

[0073] Furthermore, the intermediate transfer belt 40 of the image forming unit 30 and the conveyor belt 21 are designated as the secondary transfer position TJ2, and the intermediate transfer belt 60 of the image forming unit 50 and the conveyor belt 21 are designated as the secondary transfer position TK2. Additionally, the secondary transfer position TK2 is the downstream secondary transfer position.

[0074] As described above, the image forming unit 30 has four image forming sections 33P, 33S, 33G, and 33Gr, and an intermediate transfer belt 40 that transfers tonal images formed by the four image forming sections 33 in a single pass. Then, the image forming unit 50 is located downstream of the image forming unit 30 in the paper transport direction, and has four image forming sections 53Y, 53M, 53C, and 53K, and an intermediate transfer belt 60 that transfers tonal images formed by the four image forming sections 53 in a single pass. Then, a secondary transfer section 74 is provided corresponding to the image forming unit 30, and transfers the tonal images formed on the intermediate transfer belt 40 onto the paper PP being transported along the paper transport path. Furthermore, a secondary transfer section 76 is provided corresponding to the image forming unit 50, and transfers the tonal images formed on the intermediate transfer belt 60 onto the paper PP being transported along the paper transport path.

[0075] [Control Device]

[0076] Next, use Figure 3 The control device 80 that controls the operation of the image forming apparatus 10 will be described.

[0077] like Figure 3 As shown, the image forming unit 30, image forming unit 50, transmission unit 11, and communication unit 90 are electrically connected to the control device 80.

[0078] like Figure 3 As shown, the control device 80 includes a CPU 81 (Central Processing Unit), ROM 82 (Read Only Memory), RAM 83 (Random Access Memory), a hard disk drive, and other storage devices 85, as well as input / output interfaces (I / O) 84 that allow data input and output between the device and other devices via a network. These components are interconnected via a control bus.

[0079] Here, an image forming control program (not shown) that is executed by the CPU 81 is stored in ROM 82. Then, the CPU 81 reads the image forming control program (not shown) from ROM 82 and expands it into RAM 83, thereby executing the printing process based on the image forming control program (not shown).

[0080] Furthermore, the I / O84 is connected to the image forming unit 30, the image forming unit 50, the transmission unit 11, and the communication unit 90. The communication unit 90 is an interface for data communication between a terminal device such as a personal computer and the image forming apparatus 10.

[0081] The control device 80 performs various controls for forming toner images on the intermediate transfer belt 40 by the image forming units 32 of each color of the image forming unit 30. Similarly, the control device 80 performs various controls for forming toner images on the intermediate transfer belt 60 by the image forming units 50 of each color.

[0082] Furthermore, the control device 80 controls the developing bias voltage applied to the developing rollers 39 and 59 of the developing devices 36 and 56, respectively. Also, the control device 80 controls the transfer bias voltage applied to the secondary transfer rollers 24 and 25, respectively.

[0083] Furthermore, the control device 80 controls the timing, duration, and amount of toner supply from each color toner cartridge to the developing devices 36 and 56.

[0084] [Image forming process]

[0085] Next, a general description of the image forming process in the image forming apparatus 10 will be given.

[0086] First, the control device 80 controls each image forming unit 32 to form a toner image on the intermediate transfer belt 40 of the image forming unit 30. Similarly, the control device 80 controls each image forming unit 52 to form a toner image on the intermediate transfer belt 60 of the image forming unit 50.

[0087] Specifically, the control device 80 applies a voltage to the charged components 34 and 54, causing the surfaces of the photoreceptors 33 and 53 to become charged through the voltage-applied charged components 34 and 54, reaching a predetermined potential. Next, based on image data acquired via the communication unit 90, the control device 80 exposes the charged surfaces of the photoreceptors 33 and 53 to the exposure devices 35 and 55, forming an electrostatic latent image. Thus, an electrostatic latent image corresponding to the image data is formed on the surface of the photoreceptors 33 and 53.

[0088] Next, the control device 80 develops the electrostatic latent image formed by the exposure devices 35 and 55 through the developing devices 36 and 56, making it visible as a tonal image. Furthermore, the control device 80 overlaps and transfers the tonal images formed on the surfaces of the photoreceptors 33 and 53 of each color onto the intermediate transfer belts 40 and 60 through the primary transfer rollers 37 and 57.

[0089] Thus, in image forming unit 30, for example, a toner image superimposed with fluorescent pink (P), silver (S), gold (G), and fluorescent green (Gr) toners is formed on intermediate transfer belt 40. Similarly, in image forming unit 50, for example, a toner image superimposed with yellow (Y), magenta (M), cyan (C), and black (K) toners is formed on intermediate transfer belt 60.

[0090] Here, the paper PP, fed from the paper storage section 12 to the conveying path 19 by the feed roller 13, is conveyed to the secondary transfer position TJ2 after the conveying timing is adjusted by the two positioning rollers 15 under the control of the control device 80. At this secondary transfer position TJ2, the paper PP is conveyed between the support roller 42 and the secondary transfer roller 24, thereby transferring the toner image from the outer peripheral surface of the intermediate transfer belt 40 onto the paper PP. Then, the paper PP with the toner image transferred is conveyed downstream in the conveying direction and arrives at the secondary transfer position TK2 downstream in the conveying direction.

[0091] At this time, the control device 80 adjusts the timing of the start of image formation so that the toner image formed on the intermediate transfer belt 60 of the image forming unit 50 overlaps and is transferred onto the toner image on the paper PP conveyed from the upstream side of the conveying direction.

[0092] Paper PP, which has overlaid and transferred tones of various colors formed by image forming unit 30 and image forming unit 50, is fixed by the fixing roller 16 of fixing unit 18 and discharged by discharge roller 17 to discharge section 9 provided on the upper part of image forming apparatus body 10A.

[0093] By adopting the structure described above, the image forming apparatus 10 of this embodiment can not only use toners of the basic color CMYK, but also toners of special colors other than CMYK to form images. This image forming apparatus 10 uses the following structure: two image forming units 30 and 50, each equipped with a plurality of image forming sections 32 and 52 for forming toner images, are used to form toner images on paper. In each image forming unit 30 and 50, the toner image formed by the plurality of image forming sections 32 and 52 is transferred once onto intermediate transfer belts 40 and 60, which serve as intermediate transfer bodies. The toner image on the intermediate transfer belts 40 and 60 is then transferred a second time onto the paper PP conveyed by the transport device 20. That is, when using two image forming units 30 and 50 to form toner images on paper, a second transfer is performed at two secondary transfer positions TJ2 and TK2.

[0094] Here, the paper PP conveyed to the secondary transfer positions TJ2 and TK2 needs to be conveyed at a predetermined timing synchronized with the image formation timing. Therefore, the paper conveyed by the feed roller 14 is conveyed to the secondary transfer positions TJ2 and TK2 by adjusting the conveying timing via a paper position adjustment roller called the positioning roller 15. Then, when the conveying speed based on the feed roller 14 is different from the conveying speed based on the positioning roller 15, the conveying speed changes as the paper PP passes through the feed roller 14 and the positioning roller 15.

[0095] However, if the conveying speed of the paper PP changes while the paper has undergone secondary transfer at two secondary transfer positions TJ2 and TK2, this speed change is simultaneously transmitted to both secondary transfer positions TJ2 and TK2. Then, this speed change is simultaneously transmitted to the plurality of image forming units 32 and 52 via the intermediate transfer belts 40 and 60 of each of the two image forming units 30 and 50. As a result, it is possible that the image formation in the plurality of image forming units 32 and 52 will be affected, causing misalignment in the formed images.

[0096] refer to Figure 4 The mechanism of misalignment that occurs when the speed variation of the paper PP is simultaneously transmitted to the two secondary transfer positions TJ2 and TK2 is explained. Furthermore, Figure 4 In this description, only the structures necessary for explanation are shown in the structure constituting the image forming apparatus 10, and other structures are omitted. The same applies to the figures in the following description.

[0097] The paper PP fed from the paper storage section 12 is conveyed to the positioning roller 15 at an increased conveying speed via the feed roller 14. However, the positioning roller 15 conveys the incoming paper PP to the secondary transfer position TJ2 of the conveying device 20 at a predetermined conveying time. The positioning roller 15 is set to convey at a slightly faster speed than the feed roller 14.

[0098] However, the conveying speed at the secondary transfer position TJ2 is set to be slower than the conveying speed of the positioning roller 15. Therefore, the paper PP is conveyed to the secondary transfer position TJ2 while its conveying speed decreases as it passes through the positioning roller 15.

[0099] Thus, the conveying speed of the paper PP changes when the positioning roller 15 is added. Therefore, if the paper PP reaches the two secondary transfer positions TJ2 and TK2 while still passing through the positioning roller 15, the speed change of the paper PP is transmitted from the two secondary transfer positions TJ2 and TK2 to the intermediate transfer belts 40 and 60, respectively. As a result, the speed change is also transmitted to the primary transfer positions TP1, TS1, TG1, TGr1 and TY1, TM1, TC1, TK1 in the image forming units 30 and 50. Therefore, the speed change is also transmitted to the photoreceptors 33P, 33S, 33G, 33Gr and 53Y, 53M, 53C, 53K, and the overlapping positions of the tonal images of each color are misaligned. Moreover, since the timing of the secondary transfer at the two secondary transfer positions TJ2 and TK2 is different, different colors at the two secondary transfer positions TJ2 and TK2 are misaligned.

[0100] An example of such misalignment between colors is shown below. Figure 5 middle. Figure 5 (A) is a diagram representing the state where misalignment occurs between YMCK colors. Furthermore, Figure 5 (B) is a diagram representing the misalignment state between PSGGr colors, which are special colors. (See reference) Figure 5 It can be seen that the speed variation is transmitted to the photoreceptors 33P, 33S, 33G, 33Gr and 53Y, 53M, 53C and 53K through the intermediate transfer belts 40 and 60, and misalignment occurs in the overlap of the colors.

[0101] Therefore, in the image forming apparatus 10 of this embodiment, by setting it as follows Figure 6 The structure shown prevents changes in the conveying speed of the paper PP as it passes through the positioning roller 15 from being simultaneously transmitted to the two secondary transfer positions TJ2 and TK2. Figure 6 This is a diagram showing the positional relationship between the positioning roller 15 and the secondary transfer position TK2.

[0102] refer to Figure 6 It can be seen that the distance between the positioning roller 15, which is configured as a paper position adjustment roller, and the secondary transfer position TK2, which is subjected to secondary transfer by the secondary transfer unit 76, becomes longer than the length of the largest paper in the conveying direction, i.e., the maximum paper length, of the paper with the largest paper size that can be used.

[0103] For example, suppose the largest possible paper size is A4 (210mm × 297mm). In this case, the length of the A4 paper in the conveying direction is 297mm, therefore the maximum paper length is also 297mm. Therefore, the positional relationship between the image forming unit 50 and the positioning roller 15 is set such that the distance between the positioning roller 15 and the secondary transfer position TK2 is 297mm or more. Furthermore, Figure 6 In the text, PP indicates the paper size as A4.

[0104] By setting it to this structure, refer to Figure 6 During the period when the paper PP is sandwiched between the positioning rollers 15, the leading edge of the paper PP does not reach the secondary transfer position TK2.

[0105] Therefore, the speed variation that occurs when the paper PP passes through the positioning roller 15 will not be transmitted to the secondary transfer position TK2. As a result, the speed variation will not be transmitted to the photoreceptors 53Y, 53M, 53C, and 53K in the image forming unit 50.

[0106] That is, by preventing the speed variation of the paper PP as it passes through the positioning roller 15 from being simultaneously transmitted to the two secondary transfer positions TJ2 and TK2, the misalignment between the colors of the tonal image formed in the image forming unit 50 is suppressed.

[0107] Furthermore, even with the structure described above, speed variations occurring when the paper PP passes through the positioning roller 15 will be transmitted to the secondary transfer position TJ2. However, there is a technique in which image processing is performed on the image data used to form the toner image, and the positional correction of the toner images of each color is performed, thereby correcting misalignment between colors. By using this technique, it is possible to correct misalignment occurring in one area on the paper. However, even using this technique, it is difficult to correct misalignment occurring in more than two areas on the paper. Therefore, when speed variations occurring when the paper PP passes through the positioning roller 15 are simultaneously transmitted to two secondary transfer positions TJ2 and TK2, causing misalignment in two areas on the paper, it is difficult to perform misalignment correction.

[0108] That is, by limiting the secondary transfer position to 1 point through which the speed variation that occurs when the paper PP passes through the positioning roller 15 is transmitted, it is possible to suppress the misalignment between colors on the paper.

[0109] Moreover, such as Figure 4As shown, if the leading edge of the paper PP reaches the secondary transfer position TK2 before it finishes passing through the positioning roller 15, the paper PP will be pressed at three points: the positioning roller 15, the secondary transfer positions TJ2 and TK2. Therefore, when the speed change occurring when the paper PP passes through the positioning roller 15 is transmitted to the two secondary transfer positions TJ2 and TK2, it is difficult to predict what kind of misalignment will occur due to the interaction between the two secondary transfer positions TJ2 and TK2. Therefore, if the speed change occurring when the paper PP passes through the positioning roller 15 is transmitted to both secondary transfer positions TJ2 and TK2 simultaneously, it is more difficult to correct the misalignment compared to the case where the speed change is only transmitted to one secondary transfer position TJ2.

[0110] Additionally, the fixing unit 18 fixes the toner image on the paper after the secondary transfer by the secondary transfer unit 76 onto the paper PP. At this time, the fixing unit 18 fixes the toner image on the paper PP while the conveying speed of the paper PP conveyed on the paper conveying path is reduced at the fixing position.

[0111] Thus, speed variations also occur in the fixing unit 18, therefore, in the image forming apparatus 10 of this embodiment, such as Figure 7 As shown, the distance between the fixing position where the toner image is fixed to the paper by the fixing unit 18 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. Figure 7 This is a diagram showing the positional relationship between the fixing roller 16 of the fixing section 18 and the secondary transfer position TJ2.

[0112] refer to Figure 7 It can be seen that by setting it to this structure, the speed variation of the paper PP when passing through the fixing part 18 can be prevented from being transmitted to the two secondary transfer positions TJ2 and TK2 at the same time.

[0113] Next, the positional relationship between the positioning roller 15 and the secondary transfer position TJ2 is shown in... Figure 8 If the position of the positioning roller 15 is set too low to extend the distance between the positioning roller 15 and the secondary transfer position TJ2, the distance between the positioning roller 15 and the secondary transfer position TJ2 will become too long. Then, if the distance between the positioning roller 15 and the secondary transfer position TJ2 becomes too long, the paper PP, which is short in length, may fall off between the positioning roller 15 and the secondary transfer position TJ2 when it is to be conveyed.

[0114] Therefore, in the image forming apparatus 10 of this embodiment, the distance between the positioning roller 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 length of the smallest paper in the conveying direction, i.e., the minimum paper length, among the paper that can be used.

[0115] For example, suppose the smallest sheet of paper that can be used is L-size photographic paper (89mm × 127mm). In this case, the length of the L-size photographic paper in the transport direction is 127mm, therefore the minimum paper length is also 127mm. Therefore, the positional relationship between the image forming unit 30 and the positioning roller 15 is set such that the distance between the positioning roller 15 and the secondary transfer position TJ2 is shorter than 127mm. Furthermore, Figure 8 In this context, PP indicates that the paper size is the L-size of the photograph.

[0116] Next, the structure when the paper feeding device 100 is subsequently installed into the image forming apparatus 10 is illustrated in the figure. Figure 9 middle.

[0117] Optionally, the paper feeding device 100 can be installed after the image forming apparatus 10. This paper feeding device 100 includes a paper storage section 12A, a feed roller 13A, a feed roller 14A, and a positioning roller 15A. Thus, in a structure where the paper feeding device 100 is subsequently installed into the image forming apparatus 10, it becomes a structure having two paper storage sections 12, 12A that respectively store a plurality of papers of different sizes, and a plurality of positioning rollers 15, 15A corresponding to the two paper storage sections 12, 12A.

[0118] When feeding paper to the image forming apparatus 10 using this post-installed paper feeding device 100, it is configured to store larger sheets of paper in the paper storage section 12, 12A that is farther from the secondary transfer position TJ2. With this configuration, when using multiple sheets of different sizes, the distance between the positioning roller and the secondary transfer position TJ2 can be longer than the maximum sheet length.

[0119] For example, if A3-sized paper is stored in the paper storage section 12A on the paper feeding device 100 side, it is easy for the distance between the positioning roller 15A and the secondary transfer position TJ2 to be longer than the length of the A3-sized paper in the conveying direction.

[0120] In the above embodiments, processor refers to processor in a broad sense, including general-purpose processors (e.g., CPU: Central Processing Unit, etc.) or dedicated processors (e.g., GPU: Graphics Processing Unit, ASIC: Application Specific Integrated Circuit, FPGA: Field Programmable Gate Array, Programmable Logic Device, etc.).

[0121] Furthermore, the operations of the processors in the above embodiments can be performed not only by a single processor, but also by a plurality of processors located in physically separate positions. Moreover, the order of the processor's operations is not limited to the order described in the above embodiments and can be appropriately varied.

[0122] In this embodiment, "system" includes both a system consisting of a plurality of devices and a system consisting of a single device.

[0123] [Postscript]

[0124] The following are descriptions of the methods of the present invention. (((1)))

[0126] An image forming apparatus comprising:

[0127] The first image forming unit has a plurality of first image forming sections and a first intermediate transfer body, wherein the first intermediate transfer body transfers a tonal image formed by the plurality of the first image forming sections at one time;

[0128] The second image forming unit is located downstream of the first image forming unit in the paper transport direction, and has a plurality of second image forming sections and a second intermediate transfer body, wherein the second intermediate transfer body transfers a tonal image formed by the plurality of second image forming sections at one time.

[0129] The first secondary transfer unit is provided corresponding to the first image forming unit, and transfers the toner image formed on the first intermediate transfer body to the paper conveyed on the paper transport path.

[0130] The second secondary transfer unit, corresponding to the second image forming unit, performs a secondary transfer of the toner image formed on the second intermediate transfer body onto the paper being transported along the paper transport path; and

[0131] The paper position adjustment roller conveys the supplied paper to the first secondary transfer position where the second secondary transfer is performed by the first secondary transfer unit at a predetermined time.

[0132] The distance between the paper position adjustment roller and the second transfer position where the second transfer is performed by the second transfer unit is longer than the length of the largest paper in the conveying direction, i.e., the maximum paper length, among the possible paper sizes. (((2)))

[0134] The image forming apparatus according to (((1))) further includes a fixing unit, which fixes the toner image on the paper after it has been transferred twice by the second secondary transfer unit onto the paper.

[0135] The distance between the fixing position of the tonal image on the paper by the fixing unit and the first secondary transfer position of the second secondary transfer unit is longer than the maximum paper length. (((3)))

[0137] According to the image forming apparatus described in ((2)), wherein,

[0138] The fixing unit fixes the toner image on the paper at a state where the conveying speed of the paper being conveyed on the paper conveying path is reduced at the fixing position. (((4)))

[0140] The image forming apparatus according to any one of ((1))) to ((3))) wherein,

[0141] The distance between the paper position adjustment roller and the first secondary transfer position where the second transfer is performed by the first secondary transfer unit is shorter than the length of the smallest paper in the conveying direction, i.e., the minimum paper length, among the papers that may be used. (((5)))

[0143] The image forming apparatus according to ((4)) further includes a paper feed roller that supplies paper stored in the paper storage section to the paper position adjusting roller.

[0144] The paper position adjustment roller increases the conveying speed of the paper supplied by the paper feed roller and conveys it to the first secondary transfer position. (((6)))

[0146] The image forming apparatus according to any one of ((1))) to ((5))) comprises: a plurality of paper storage sections for storing a plurality of papers of different sizes; and a plurality of paper position adjusting rollers corresponding to the plurality of paper storage sections.

[0147] The image forming apparatus is configured to store large-sized sheets of paper in the paper storage section that is far from the first secondary transfer position among the plurality of paper storage sections.

[0148] The effects of the appendix-based structure are described below.

[0149] According to the image forming apparatus (((1)), it is possible to prevent the change in the conveying speed of the paper as it passes through the paper position adjustment roller from being transmitted to the two secondary transfer positions simultaneously.

[0150] According to the image forming apparatus (((2))), it is possible to prevent the change in the conveying speed of the paper as it passes through the fixing section from being transmitted to the two secondary transfer positions simultaneously.

[0151] According to the image forming apparatus ((3)), it is possible to prevent the change in conveying speed when the paper passes through the fixing section and the conveying speed decreases, and simultaneously transmit it to the two secondary transfer positions.

[0152] According to the image forming apparatus ((4)), even when using paper with the smallest paper size, it is possible to prevent the paper from falling off between the paper position adjustment roller and the first secondary transfer position.

[0153] According to the image forming apparatus ((5)), it is possible to prevent the change in the conveying speed of the paper as it passes through the paper feed roller and the paper position adjustment roller from being transmitted to the two secondary transfer positions simultaneously.

[0154] According to the image forming apparatus ((6)), when using multiple sheets of paper with different paper sizes, the distance between the paper position adjustment roller and the second transfer position can be longer than the maximum paper length.

[0155] The embodiments of the present invention described above are provided for illustrative purposes. Furthermore, these embodiments do not encompass the entirety of the invention, nor do they limit the invention to the disclosed methods. It will be apparent to those skilled in the art that various modifications and variations will be readily understood. These embodiments were chosen and described to most readily explain the principles and applications of the invention. Thus, those skilled in the art can understand the invention through various modifications that are assumed to be optimized for specific uses of various embodiments. The scope of the invention is defined by the foregoing claims and their equivalents.

[0156] Symbol Explanation

[0157] 9-Discharge section, 10-Image forming apparatus, 10A-Image forming apparatus body, 11-Transfer section, 12, 12A-Paper storage section, 13, 13A-Feed roller, 14, 14A-Paper feed roller, 15, 15A-Positioning roller, 16-Fixing roller, 17-Discharge roller, 18-Fixing section, 19-Transfer path, 20-Transfer device, 21-Conveyor belt, 22, 23-Support roller, 24, 25-Secondary Transfer roller, 30-image forming unit, 32-image forming section, 32P, 32S, 32G, 32Gr-image forming section, 33P, 33S, 33G, 33Gr-photoreceptor, 34-charged component, 35-exposure device, 36-developing device, 37P, 37S, 37G, 37Gr-primary transfer roller, 39-developing roller, 40-intermediate transfer belt, 42-support roller, 44-support roller 50 - Image forming unit; 52Y, 52M, 52C, 52K - Image forming section; 53Y, 53M, 53C, 53K - Photosensitive element; 54 - Charged component; 55 - Exposure device; 56 - Developing device; 57Y, 57M, 57C, 57K - Primary transfer roller; 59 - Developing roller; 60 - Intermediate transfer belt; 62 - Support roller; 64 - Support roller; 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 - Communication unit; 100 - Paper feeding device; PP - Paper; TJ2, TK2 - Secondary transfer position; TP1, TS1, TG1, TGr1 - Primary transfer position; TY1, TM1, TC1, TK1 - Primary transfer position.

Claims

1. An image forming apparatus comprising: The first image forming unit has a plurality of first image forming sections and a first intermediate transfer body, wherein the first intermediate transfer body transfers a tonal image formed by the plurality of the first image forming sections at one time; The second image forming unit is located downstream of the first image forming unit in the paper transport direction, and has a plurality of second image forming sections and a second intermediate transfer body, wherein the second intermediate transfer body transfers a tonal image formed by the plurality of second image forming sections at one time. The first secondary transfer unit is provided corresponding to the first image forming unit, and transfers the toner image formed on the first intermediate transfer body to the paper conveyed on the paper transport path. The second secondary transfer unit, corresponding to the second image forming unit, performs a secondary transfer of the toner image formed on the second intermediate transfer body onto the paper being transported along the paper transport path; and The paper position adjustment roller conveys the supplied paper to the first secondary transfer position where the second secondary transfer is performed by the first secondary transfer unit at a predetermined time. The distance between the paper position adjustment roller and the second transfer position where the second transfer is performed by the second transfer unit is longer than the length of the largest paper in the conveying direction, i.e., the maximum paper length, among the possible paper sizes.

2. The image forming apparatus according to claim 1, further comprising a fixing unit, the fixing unit fixing the toner image on the paper after the second secondary transfer unit has performed a secondary transfer onto the paper. The distance between the fixing position of the tonal image on the paper by the fixing unit and the first secondary transfer position of the second secondary transfer unit is longer than the maximum paper length.

3. The image forming apparatus according to claim 2, wherein, The fixing unit fixes the toner image on the paper at a state where the conveying speed of the paper being conveyed on the paper conveying path is reduced at the fixing position.

4. The image forming apparatus according to any one of claims 1 to 3, wherein, The distance between the paper position adjustment roller and the first secondary transfer position where the second transfer is performed by the first secondary transfer unit is shorter than the length of the smallest paper in the conveying direction, i.e., the minimum paper length, among the papers that may be used.

5. The image forming apparatus according to claim 4, further comprising a paper feed roller that supplies paper stored in the paper storage section to the paper position adjusting roller. The paper position adjustment roller increases the conveying speed of the paper supplied by the paper feed roller and conveys it to the first secondary transfer position.

6. The image forming apparatus according to any one of claims 1 to 5, comprising: a plurality of paper storage sections for storing a plurality of papers of different sizes; and a plurality of paper position adjusting rollers corresponding to the plurality of paper storage sections. The image forming apparatus is configured to store large-sized sheets of paper in the paper storage section that is far from the first secondary transfer position among the plurality of paper storage sections.

Images